Chevrolet Light Duty Truck 1973 Service Manual

Document

FOREWORD
This manual includes theory of operation and procedures
for diagnosis, maintenance and adjustments, minor service
operations, and removal and installation for components of
Chevrolet Light Duty Trucks. Procedures involving dis&shy;
assembly and assembly of major components for these
vehicles are contained in the 1973 Chevrolet Passenger Car
and Light Duty Truck Overhaul Manual. Wiring diagrams for
1973 trucks are contained in a separate Wiring Diagram
Booklet.
The Section Index on the contents page enables the user to
quickly locate any desired section. At the beginning of each
section containing more than one major subject is a Table of
Contents, which gives the page number on which each major
subject begins. An Index is placed at the beginning of each
major subject within the section.
Summaries of Special Tools, when required, are found at
the end of major sections while specifications covering
vehicle components are presented at the rear of the manual.
This manual should be kept in a handy place for ready
reference. If properly used, it will enable the technician to
better serve the owners of Chevrolet vehicles.
All information, illustrations and specifications contained
in this literature are based on the latest product information
available at the time of publication approval. The right is
reserved to make changes at any time without notice.
CHEVROLET MOTOR DIVISION
General Motors Corporation
DETROIT, MICHIGAN
IMPORTANT SAFETY NOTICE
Proper service and repair is important to the safe, reliable operation of all
motor vehicles. The service procedures recommended and described in this
service manual are effective methods, for performing service operations.
Some of these service operations require the use of tools specially designed
for the purpose. The special tools should be used when and as recommended.
#
It is important to note that some warnings against the use of specific service
methods that can damage the vehicle or render it unsafe are stated in this
service manual. It is also important to understand these warnings are not
exhaustive. We could not possibly know, evaluate and advise the service
trade of all conceivable ways in which service might be done or of the
possible hazardous consequences of each way. Consequently, we have not
undertaken any such broad evaluation. Accordingly, anyone who uses a
service procedure or tool which is not recommended by the manufacturer
must first satisfy himself thoroughly that neither his safety nor vehicle safety
will be jeopardized by the service method he selects.
S E C T IO N IN D E X
SECTION
0
1A
IB
2
3
4
5
6
6K
6M
6T
6Y
7
8
9
10
11
12
13
14
15
1973
LIGHT DUTY
TRUCK
(SERIES 10-30)
SERVICE
MANUAL
NAME
GENERAL INFORMATION
AND LUBRICATION
HEATER AND
AIR CONDITIONING
BODY
FRAME
FRONT SUSPENSION
4-WHEEL DRIVE
REAR SUSPENSION
AND DRIVELINE
BRAKES
ENGINE
ENGINE COOLING
FUEL SYSTEM
EMISSION CONTROL
SYSTEMS
ENGINE ELECTRICAL
CLUTCH AND TRANSMISSION
FUEL TANK AND
EXHAUST SYSTEM
STEERING
WHEELS AND TIRES
CHASSIS SHEET METAL
ELECTRICAL— BODY
AND CHASSIS
RADIATOR AND GRILLE
BUMPERS
ACCESSORIES
SPECIFICATIONS
&copy;
1972 General Motors Corporation
Printed in U.S.A.
GENERAL IN F O R M A T IO N A N D L UBRICATION
0-1
SECTION 0
GENERAL INFORMATION AND LUBRICATION
CONTENTS OF THIS SECTION
I
General Inform ation........................................................................ 0-1
Lubrication........................................................................................... 0-12
GENERAL INFO RM ATIO N
INDEX
Model Line U p ................................................................. .....0-1
Truck Model Designation............................................... .....0-1
Vehicle Identification Number and Rating Plate .........0-1
Engine Number................................................................. .....0-2
Unit and Serial Number Locations ............................ .....0-2
MODEL LINE UP
The 10 through 35 Series truck model line-up for 1973
consists of the models shown in the Charts in this
section.
Truck Model Designation
A five digit number preceded by a letter is used to
designate truck models. For example, vehicle C 10703
would be: Conventional C, 4500 lbs.-6800 lbs. GVW _l_j
42 in. -47 in. Cab-to-Axle dimension 07, Chassis cab 03,
as listed below.
Service Parts Identification Plate .................. ...................0-2
Keys and Locks ................................................ ...................0-3
Emergency Starting .......................................... ...................0-3
Towing.................................................................. ...................0-4
Load Capacity Chart ...................................... ...................0-4
08 - 48-53 in.
09 - 54-59 in.
10 - 60-65 in.
14 - 84-89 in.
Fourth and Fifth Numbers-Body Styles
C - Conventional (Conventional Cab, Suburban)
G - Light Duty Forward Control
K - Four-Wheel Drive
P - Forward Control
Pickup boxes, tailgate and drop glass, van bodies, and
trim are options.
03.- Cab
05 - Van (windowless)
06 - Suburban and Van (with windows)
14 - Utility
32 - Motor Home Chassis
42 - Forward Control Chassis
63 - Four-Door Crew Cab
First Number-GVW Range
VEHICLE IDENTIFICATION NUMBER
AND RATING PLATE
First Letter • Chassis
J_- 4500-7150 lbs.
2 - 5500-8200 lbs.
3 - 6200-14000 lbs.
Second and Third NumbersCab-To-Axle Dimension
05 - 30-35 in.
07 - 42-47 in.
A combination vehicle identification number and rating
plate used on all models (fig. 1) is located on the left
door pillar, except on School Bus, and some Forward
Control Motor Home models. On School Bus models the
plate is attached to the air intake plenum panel. On
Forward Control models (P10, P20, P30 except P30
Motor Home Chassis) it is attached to the dash and toe
panel.
The vehicle identification num ber stamped on the plate
decodes into the information shown in Figure 2.
LIGHT DUTY TRUCK SERVICE MANUAL
0 -2 GENERAL IN F O R M A TIO N A N D LU B R IC A TIO N
ENGINE
DESIGNATION
ENGINE NUMBER
The engine number indicates manufacturing plant,
month and day of manufacture, and transmission type.
A typical engine number would be F1210TFA, which
would breakdown thus:
F - M anufacturing Plant (F-Flint, T-Tonawanda)
12 - Month of Manufacture (December)
10 - Day of Manufacture (tenth)
T - Truck
FA - Transmission and engine type
UNIT AND SERIAL NUMBER LOCATIONS
For the convenience of service technicians and engineers
when writing up certain business papers such as
W arranty Reports, Product Information Reports, or
reporting product failures in any way, the location of the
various unit numbers have been indicated. These unit
numbers and their prefix or suffix are necessary on these
papers for various reasons - such as accounting, followup on production, etc.
The prefixes on certain units identify the plant in which
the unit was manufactured and thereby permits proper
follow-up of the plant involved to get corrections made
when necessary.
Always include the prefix in the number.
Axles
• Series 10 Rear Axle Serial Number Located at the
Bottom Flange of Carrier Housing.
• Series 20-30 Rear Axle Located at the Forward
Upper Surface of Carrier.
Transmissions
• 3-Speed Transmission Unit Number Located on
Lower Left Side of Case Adjacent to Rear of Cover.
• 4-Speed Transmission Unit Num ber Stamped on
Rear of Case, Above Output.
w
G E N E R A L M O T O R S C O R P O R A T IO N
w
WARRANTY MAY BE VOIDED IF WEIGHT EXCEEDS ANY OF RATINGS SHOWN. GROSS
VEHICLE WEIGHT INCLUOES WEIGHT OF BASE TRUCK, ALL ADOED EQUIPMENT, DRIVER
AND PASSENGERS, AND ALL PROPERTY LOADED INTO TRUCK.
* REFER TO OWNERS MANUAL FOR EQUIPMENT REQUIRED FOR INTERMEDIATE ORMAXIMUM
GVW RATINGS, AND FOR OTHER LOADING INFORMATION, INCLUDING TIRE INFLATION.
DIVISION
Q = L6-2 5 0
T = L 6-292
X = V8
Y = V8
Z — V8
MODEL YEAR
C = CHEVROLET
T = GMT
3 = 1973 fo r all
Series.
SEQUENTIAL NUMBER
CHASSIS T Y P E
C = 2 WHEEL DRIVE
G = L IG H T DUTY
FO RW ARD CO NTRO L
K = 4 WHEEL DRIVE
P = FO RW AR D C O NTRO L
BODY
2-Forw ard Control
chassis only
3-Cab-chassis
4-C a b a n d pickup
5-F orw ard Control
chassis only
(S teel-A lum inum
6-S ub urban body
ASSEMBLY PLANT
A -L ak ew o o d
STYLE
B -B altim ore
C-So uth gate
D -D o raville
F-Flint
box
G -F ra m in g h a m
J-Janesville
K-Leeds
Body) L-Van N uys
N -N o rw o o d
V -G M Truck-Pontiac
R -A rlington
S-St. Louis
T-Tarrytow n
U-Lordstown
W -W illo w Run
Y -W ilm in g to n
Z-Frem ont
1-Oshawa
2-Ste. Therese
7-Forw ard Control
(Rec. Vehicle Chassis)
8-U tility (Blazer)
Fig. 2—Vehicle Identification Number
• Turbo Hydra-Matic 350 Transmission Unit Number
Located on Right Rear Vertical Surface of Oil Pan.
• The Turbo Hydra-Matic Transmission 400 Serial
Number is Located on the Light Blue Plate on the
Right Side of the Transmission.
Engines
• 6-Cylinder Engine
Right Hand Side
Distributor.
• 8-Cylinder Engine
Front, Right Hand
Unit N um ber Located on Pad at
of Cylinder Block at Rear of
Unit N um ber Located on Pad at
Side of Cylinder Block.
Deicotrons
Delcotron Unit Serial Num ber Located at Top of
Rear Housing.
Batteries
Battery Code Number Located on Cell Cover Top of
Battery.
RATINGS IN POUNDS - AS MANUFACTURED *MAXIMUM CAPABILITY
GROSS VEH IC LE W EIGHT FOR THIS VEHICLE
MAXIMUM FR O N T END W EIGHT AT GROUND
Starters
Starter Serial N um ber and Production Date
Stamped on Outer Case, Toward Rear.
M AXIMUM R EA R END W EIGHT AT GROUNO
VEHIC LE IDENTIFIC ATIO N NO.
v!
Fig. 1—Vehicle Identification Number and Rating
Plate Information
SERVICE PARTS IDENTIFICATION PLATE
The Service Parts Identification Plate (fig. 3) is provided
on all Truck models. On most series it will be located on
the inside of the glove box door, or, on Forward Control
series, it will be located on an inner body panel. The
plate lists the vehicle serial number, wheelbase, and all
Production options or Special Equipment on the vehicle
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N AND LUBRICATION
SERVICE
IN . ■
NOTE:
■
■
■
■
P A R TS
■
I D E N T I F I C A T I O N ____________
W /B A S E ■
■
■
S E B B H B
V I N —VEHICLE IDENTIFICATION NUMBER
T H E S P E C IA L E Q U IP M E N T L IS T E D B E L O W H A S BEEN IN S T A L L E D ON
IMPORTANT: RETAIN THIS PLATE AS A PERMANENT RECORD
Fig. 3—Service Parts Identification Plate
when it was shipped from the factory including paint
information. ALWAYS REFER TO THIS INFORM ATIO N
WHEN ORDERING PARTS.
KEYS AND LOCKS
Two keys are provided with each vehicle. Different lock
cylinders operated by a separate key are available as an
option for the sliding side load door and rear load doors.
EMERGENCY STARTING
• Never tow the vehicle to start because the surge
forward when the engine starts could cause a collision
with the tow vehicle.
• Engines in vehicles with automatic transmissions
cannot be started by towing or pushing the vehicle.
• To start the vehicle when the Energizer (battery) is
discharged, use a single auxiliary battery or
Energizer of the same nominal voltage (12 volts) as
the discharged battery, with suitable jum per cables.
• Make connections as set forth below under &quot;Jump
Starting With Auxiliary (Booster) Battery&quot; to lessen
the chance of personal injury or property damage.
CAUTION: Never expose battery to open flame
or electric spark-battery action generates
hydrogen gas which is flammable and explo&shy;
sive. Don’t allow battery fluid to contact skin,
eyes, fabrics, or painted surfaces-fluid is a
sulfuric acid solution which could cause serious
personal injury or property damage. Wear eye
protection when working with battery.
0-3
discharged batteries. Lay a cloth over the open vent
wells of each battery. These two actions help reduce
the explosion hazard always present in either
battery when connecting &quot;live&quot; booster batteries to
&quot;dead&quot; batteries.
3. Attach one end of one jum per cable to the positive
terminal of the booster battery (identified by a red
color, &quot; + &quot; or &quot;P&quot; on the battery case, post or
clamp) and the other end of same cable to positive
terminal of discharged battery Do NOT permit
vehicles to touch each other, as this could establish
a ground connection and counteract the benefits of
this procedure.
4. Attach one end of the remaining negative(—) cable
to the negative terminal (black color,
or &quot;N &quot;)
of the booster battery, and the other end to the
engine lift bracket on 6 cylinder models and the
delcotron mounting bracket on V-8 models (see
Figure 4) (do not connect directly to negative post
of dead battery)-taking care that clamps from one
cable do not touch the clamps on the other cable.
Do not lean over the battery when making this
connection.
Reverse this sequence exactly when removing the
jumper cables. Re-install vent caps and throw cloths
away as the cloths may have corrosive acid on them.
CAUTI0N:^4/iy procedure other than the above
could result in: (1) personal injury caused by
electrolyte squirting out the battery vents, (2)
personal injury or property damage due to
battery explosion, (3) damage to the charging
system of the booster vehicle or of the
immobilized vehicle.
L 6 ENGINE
Jump Starting With Auxiliary
(Booster) Battery
Both booster and discharged battery should be treated
carefully when using jum per cables. Follow exactly the
procedure outlined below, being careful not to cause
sparks:
1. Set parking brake and place automatic transmission
in &quot;PARK&quot; (neutral for manual transmission).
Turn off lights, heater and other electrical loads.
2. Remove vent caps from both the booster and the
V 8 ENGINE
Fig. 4—Booster Battery Cable Ground Connection
LIGHT DUTY TRUCK SERVICE MANUAL
0 -4 GENERAL IN F O R M A T IO N A N D LUBRICATIO N
PUSH STARTING
If your truck is equipped with a manual 3-speed or
4-speed transmission, it can be started in an emergency
by pushing. When being pushed to start the engine, turn
off all unnecessary electrical loads, turn ignition to
&quot;O N ,&quot; depress the clutch pedal and place the shift lever
in high gear. Release the clutch pedal when speed
reaches 10 to 15 miles per hour. Bumpers and other parts
contacted by the pushing vehicle should be protected
from damage during pushing. Never tow the truck to
start.
TOWING
All Except Four Wheel Drive Trucks
Normally your vehicle may be towed with all four wheels
on the ground for distances up to 50 miles at speeds of
less than 35 MPH. The engine should be off and the
transmission in neutral.
However, the rear wheels must be raised off the ground
or the drive shaft disconnected when the transmission is
not operating properly or when a speed of 35 MPH or
distance of 50 miles will be exceeded.
CAUTION: I f a truck is towed on its front
wheels only, the steering wheel must be secured
with the wheels in a straight ahead position.
Four Wheel Drive Trucks
It is recommended that the truck be towed with the front
wheels off the ground. The truck can be towed, however,
with the rear wheels off the ground if there is damage in
the rear wheel area. In this event, the transmission
selector lever should be placed in the &quot;N &quot; (neutral)
position and with conventional four wheel drive the
front drive disengaged. With Full Time four wheel drive
the transfer case should be in high. Towing speeds
LOAD CAPACITY Ch
The first column of the Load Capacity Chart on the
following pages shows the basic model series.
The next column reflects the wheelbases available within
each series.
The third column shows the Gross Vehicle Weight
(GVW) rating applicable to each series vehicle. GVW
means the maximum design weight of the vehicle
including the vehicle itself and all equipment added to
the vehicle after it has left the factory, the driver weight
and occupant weight and everything that is loaded into
or onto the vehicle.
Following the GVW columns are the minimum
recommended tires to qualify the vehicle for each GVW
rating.
should not exceed 35 MPH for distances up to 50 miles.
If truck is towed on its front wheels, the steering wheel
should be secured to keep the front wheels in a straight&shy;
ahead position.
When towing the vehicle at slow speeds (approx. 20
MPH), for a very short distance only, the transmission
must be in NEUTRAL and with conventional four wheel
drive the transfer case M UST be in &quot;T W O WHEEL
H IG H &quot; . With Full Time four wheel drive the transfer
case should be in high.
When towing the vehicle at faster speeds for greater
distances, the following steps MUST be taken:
• If front wheels are on the road, disconnect the front
drive shaft.
• If rear wheels are on the road, disconnect the rear
drive shaft.
STEEL TUBING REPLACEMENT
In the event that replacement of steel tubing is required
on brake line, fuel line, evaporative emission, and
transmission cooling lines, only the recommended steel
replacement tubing should be used.
Only special steel tubing should be used to replace brake
line. That is, a double wrapped and brazed steel tubing
meeting G.M. Specification 123 M. Further, any other
steel tubing should be replaced only with the released
steel tubing or its equivalent. Under no condition should
copper or aluminum tubing be used to replace steel
tubing. Those materials do not have satisfactory fatigue
durability to withstand normal vehicle vibrations.
All steel tubing should be flared using the upset (double
lap) flare method which is detailed in Section 5 of this
Manual.
\T INTERPRETATION
The tire pressures listed in the column adjacent to the
tire sizes in the chart are the minimum required tire
pressures for maximum permissible loads.
The letter under the Front and Rear Axle and Spring
columns indicates that base equipment is satisfactory to
qualify the vehicle for any given GVW rating. When the
letters &quot;RPO&quot; denoting Regular Production Option,
followed by a number appears in these columns
(example RPO G50), the vehicle must be equipped with
the extra cost equipment specified by the RPO to qualify
the vehicle for the given GVW rating.
In loading the vehicle, the combined front and rear end
weights at the ground must not exceed the GVW
specified for the vehicle as manufactured.
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N A ND LUBR IC A TION
LOADED-MAXIMUM GVW: 6000-LBSFRONT AXLE CAPACITY: 3250 LBS.
Front Curb
Front Cargo
Load
2100 lbs.
400 lbs.
2500 lbs.
REAR AXLE CAPACITY: 3582 LBS.
Rear Curb
Rear Cargo
Load
0-5
In trailer hauling applications, the vehicle rear end
weight at the ground with trailer attached must not
exceed the &quot;Maximum Rear End Weight at Ground&quot;
rating of the vehicle.
A typical example of a Truck in a loaded condition is
shown in Figure 5. Note that the axle or GVW
capabilities are not exceeded.
1585 lbs.
1915 lbs3500 lbs.
TOTAL WEIGHT AT GROUND: 6000 lbs.
Fig. 5—Typical Vehicle Loaded Condition
LIGHT DUTY TRUCK SERVICE MANUAL
.
4
0 6 GENERAL IN F O R M A T IO N A N D LUBRICATIO N
LOAD CAPACITY CHART
W HEEL
BASE
C l0514 and
C10514 + Z58 or Z59
C l0703
Cab Chassis
C10703 + E62 or E63
ickups
C10903
Cab Chassis
C10903 + E62 or E63
Pickups
106.5
•
117.5
•
117.5
•
131.5
•
131.5
C10906, and
C10906 + E55
Suburbans
129.5
C20903
Cab Chassis
131.5
C20903 + E62 or E63
Pickups
131.5
C20906, and
C20906 + E55
Suburbans
C20963
Crew Cab Chassis
C20963 + E63
GROSS
V EHICLE
W EIGHT
RATING
(POUNDS)*
129.5
4900
5200
5700
4900
5400
6000
4900
5400
6000
4900
5400
6000
4900
5400
6000
5400
6000
6800
6400
7500
8200
6400
7500
8200
6650
7500
8200
FRONT
T IR E
PRES&shy;
SURE
FRONT
TIR ES
E78-15B
G78-15B
H78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15D
8.75-16.5C
9.50-16.5D
9.50-16.5D
8.57-16.5C
9.50-16.5D
9.50-16.5D
8.75-16.5C
9.50-16.5D
9.50-16.5D
b
b
b
b
b
b
b
b
b
30
32
32
32
30
28
32
30
28
32
30
28
32
30
28
32
30
30
40
30
30
40
30
30
40
30
30
REAR
TIRES
E78-15B
G78-15B
H78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15D
8.75-16.5C
9.50-16.5D
9.50-16.5D
8.57-16.5C
9.50-16.5D
9.50-16.5D
8.75-16.5C
9.50-16.5D
9.50-16.5D
M INIMUM M A N D A T O R Y E Q U IP M E N T F O R GVW R A T IN G
GROSS
REAR
AXLE
W EIGHT
TIR E
FRONT
FRONT
REAR
PRES
RATIN G
AXLE
SPRINGS
FRONT*
AXLE
SURE
b
b
b
b
b
b
b
b
b
30
32
32
32
30
32
32
30
32
32
30
32
32
30
32
32
32
36
45
55
60
45
55
60
45
55
60
3250
3250
3250
3100
3100
3250
3100
3100
3250
3100
3100
3250
3100
3100
3250
3100
3100
3250
3800
3800
3800
3800
3800
3800
3800
3800
3800
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
3100 b
3100 b
3250 F60
3100 b
3100 b
3250 F60
3100 b
3100 b
3250 F60
3100 b
3100 b
3250 F60
3100 b
3100 b
3250 F60
3100 b
3250 F60
3250 F60
3500 b
3500 b
3800 F60
3500 b
3500 b
3800 F60
3500 b
3500 b
3800 F60
2546
2946
3218
2946
3100
3250
2946
3100
3250
2946
3100
3250
2946
3100
3250
2946
3100
3250
3500
3500
3800
3500
3500
3800
3500
3500
3800
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
5700
5700
5700
5700
5700
5700
5700
5700
5700
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
REAR
SPRINGS
GROSS
AXLE
W EIGHT
RATING
REAR*
3000 b
3000 b
3400 G50
3100 b
3100 b
4000 G50
3100 b
3100 b
4000 G50
3100 b
3100 b
4000 G50
3100 b
3100 b
4000 G50
3100 b
4000 G50
4000 G50
4000 b
5200 G50
5700 G51
4000 b
5200 G50
5700 G51
4000 b
5200 G50
5700 G51
2546
2946
3218
2946
3100
3582
2946
3100
3582
2946
3100
3582
2946
3100
3582
2946
3218
3750
3980
5200
5560
3980
5200
5560
3980
5200
5560
164.5
8200
9.50-16.5D b
35
9.50-16.5D b
60
3800 b
3800 b
3800
7500 b
5700 b
5560
164.5
8200
9.50-16.5D b
35
9.50-16.5D b
60
3800 b
3800 b
3800
7500 b
5700 b
5560
6600
8200
9000
6600
8200
9000
8.75-16.5C b
9.50-16.5D
9.50-16.5D
8.75-16.5C b
9.50-16.5D
9.50-16.5D
40
30
35
40
30
35
8.75-16.5C b
9.50-16.50
9.50-16.5E
8.75-16.5C b
9.50-16.5D
9.50-16.5E
45
60
75
45
60
75
3800
3800
3800
3800
3800
3800
3500 b
3500 b
3800 F60
3500 b
3500 b
3800 F60
3500
3500
3800
3500
3500
3800
7500
7500
7500
7500
7500
7500
4800 b
5700 G50
7000 G51
4800 b
5700 G50
7000 G51
3980
5560
6340
3980
5560
6340
C30903
Cab Chassis w ith
single rear wheels
131.5
C30903 + E62 or E63
Pickups
131.5
b
b
b
b
b
b
b
b
b
b
b
b
REQUIRED
OPTIONS
J70
J70
J70
J70
J70
J70
J70
J70
AS3 or A T 5
* Refer to the Gross Vehicle Weight Rating plate on the vehicle. Gross A xle Weight Rating-Front, and Gross A xle Weight Rating-Rear on this chart are based upon component
m inim um capacity o f axles, springs, or tires.
b = base equipment
RESTRICTIONS
C10703-10903 and C10703-10903 + E62 or +63, w ith LF8 V8 engines on 4900 GVWR vehicles:
RPO J70 power brakes required.
C10906 and C10906 + E55:
RPO A T5 not available on 5400 GVW.
When RPO A T 5 is used on 6000 GVWR, RPO F60 is required.
RPO AS3 available o nly on 6800 GVWR vehicles, AS3 requires F59.
When RPO AS3 or A T 5 are not specified, GVWR is restricted to 5400 or 6000.
L78-15 and 9.50-16.5 tires:
Heavy d u ty wheels are required w ith these tires, and are included when installed at the factory.
For detailed inform atio n , see tire and wheel restrictions in &quot;O w ner’s and D river’s Manual&quot;.
* - 5 3 0 0 GVW avail, these models w ith J70 Power Brakes add requirement.
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N A N D LUBRICATION
0-7
LOAD CAPACITY CHART
1973 M O D E L S
C31003
Cab Chassis w ith
single rear wheels
C31403
Cab Chassis w ith
single rear wheels
C30903 + E63
Pickup w ith
dual rear wheels
C31003
Cab Chassis w ith
dual rear wheels
C31403
Cab Chassis w ith
dual rear wheels
C30963
Crew Cab chassis w ith
W HEEL&shy;
BASE
135.5
159.5
131.5
135.5
159.5
GROSS
VEHICLE
W EIGHT
RATIN G
(POUNDS)*
M INIM UM M A N D A T O R Y E Q U I P M E N T F O R GVW R A T IN G
GROSS
REAR
AXLE
TIR E
W EIGHT
PRES
FRONT
FRONT
RATING
REAR
SURE
AXLE
SPRINGS
FRONT*
AXLE
FRONT
TIR ES
FRONT
TIR E
PRES
SURE
REAR
TIR ES
6600
8200
9000
6600
8200
9000
8.75 16.5C b
9.50 16.5D
9 50-16.5D
8.75-16.5C b
9.50-16.5D
9.50-16.5D
40
30
35
40
30
35
8.75-16.5C b
9.50-16.5D
9.50-16.5E
8.75 16.5C b
9.50-16.5D
9.50-16.5E
10000
8.75-16.5C b
45
8.75-16.5C b
8000
9000
10000
8000
9000
10000
7.00-16C
7.00-16C
7.50-16C
7.00-16C
7.0016C
7.50-16C
45
45
45
45
45
45
7.00-16C
7.00-16C
7.50-16C
7.00-16C
7.00- 16C
7.50 16C
b
b
b
b
b
b
b
b
45
60
75
45
60
75
3800
3800
3800
3800
3800
3800
REAR
SPRINGS
GROSS
AXLE
W EIGHT
RATIN G
REAR *
4800 b
5700 G50
7000 G51
4800 b
5700 G50
7000 G51
3980
5560
6340
3980
5560
6340
b
b
b
b
b
b
3500 b
3500 b
3800 F60
3500 b
3500 b
3800 F60
3500
3500
3800
3500
3500
3800
45
3800 b
3800 F60
3800
7500 Ft 05
7500 G60
7000
40
45
45
40
45
45
3800
3800
3800
3800
3800
3800
3500 b
3800 F60
3800 F60
3500 b
3800 F60
3800 F60
3500
3600
3800
3500
3600
3800
7500
7500
7500
7500
7500
7500
5700 b
7000 G51
7500 G60
5700 b
7000 G51
7500 G60
5700
6320
7260
5700
6320
7260
b
b
b
b
b
b
7500
7500
7500
7500
7500
7500
b
b
b
b
b
b
R05
R05
R05
R05
R05
R05
164.5
9000
9.50-16.5E b
35
9.50-16.5E b
75
3800 b
3800 b
3800
7500 b
7000 G51
6340
164.5
9000
9.50 16.5E b
35
9.50-16.5E b
75
3800 b
3800 F60
3800
7500 b
7000 G51
6340
164.5
10000
8.75-16.5C b
45
8.75-16 5C b
45
3800 b
3800 F60
3800
7500 R05
7500 G60
7000
164.5
10000
8 75-16.5C b
45
8.75 16.5C b
45
3800 b
3800 F60
3900
7500 R05
7500 G60
7000
REQUIRED
OPTIONS
LS9 or LF8
single rear wheels
C30963 + E63
w ith single rear wheels
C30963
Crew Cab chassis w ith
dual rear wheels
C30963 + E63
w ith dual rear wheels
Refer to the Gross Vehicle Weight Rating plate on the vehicle. Gross A xle Weight R ating-Front, and Gross A xle Weight Rating-Rear on this chart are based upon component
m inim um capacity o f axles, springs, or tires,
b = base equipment.
LIGHT DUTY TRUCK SERVICE MANUAL
r
r
—
tf-8 GENERAL IN F O R M A T IO N A N D LU BR IC A TIO N
LOAD CAPACITY CHART
1973 M O D E L S
+Z58 or +Z59
K10703
Cab Chassis
(Not Merchandised)
W HEEL&shy;
BASE
106.5
117.5
K10703 + E62 or E63
Pickups
117.5
K 10903
Cab Chassis
(Not Merchandised)
131.5
K 10903 + E62 or E63
Pickups
K 10906, and
K10906 + E55
131.5
129.5
GROSS
VEHICLE
W EIGHT
R A TIN G
(POUNDS) #
4900
5350
5800
6200
5200
5600
6000
5200
5600
6000
5200
5600
6000
5200
5600
6000
5600
6000
6600
7150
6800
K20903
Cab Chassis
131.5
7500
8200
6800
K20903 + E62 or E63
Pickups
131.5
7500
8200
6800
K20906, and
K 2 0 9 0 6 + E55
Suburbans
129.5
7500
8200
MINIMUM M A N D A T O R Y EQ U IP M EN T FO R GVW R A T IN G
GROSS
REAR
AXLE
TIR E
W EIGHT
PRES&shy;
FRONT
FRONT
RATING
REAR
REAR
SURE
AXLE
SPRINGS F R O N T *
AXLE
SPRINGS
FRONT
TIR E
FRONT
TIRES
E78-15B
G 78 1 5B
H78-15B
H78-15B
G78-15B
H78-15B
L 7815B
G78 15B
H78-15B
L78-15B
G78-15B
H78-15B
L 7815B
G 7815B
H78 15B
L78-15B
G 7815B
H78 15B
L78-15B
L78-15D
8.75 16.5C
or 7.50-16C
8.75-16.5C
or 7.50-16C
9.50-16.5D
or 7.50 16C
8.75-16.5C
or 7.50-16C
8.75-16.5C
or 7.50-16C
9.50-16.5D
or 7.50 16C
8.75 16 5C
or 7.50 16C
8.75-16.5C
or 7.50-16C
9.50-16.5D
or 7.50-16C
PRES&shy;
SURE
b
b
b
b
b
b
b
b
b
b
32
32
32
32
. 32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
40
40
40
40
30
40
40
40
40
40
30
40
40
40
40
40
30
40
REAR
TIRES
E78-15B
G 78 1 5B
H 7815B
H78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
G78-15B
H78-15B
L78-15B
L78-15D
8.75-16.5C
or 7.50-16C
8.75-16.5D
or 7.50-16D
9.50-16.5D
or 7.50-16E
8,75-16.5C
or 7.50-16C
8.75-16.5D
or 7.50 16D
9.50-16.5D
or 7.50-16E
8.75-16.5C
or 7.50 16C
8.75-16.5D
7.50-16D
9.50-16.5D
7.50-16E
b
b
b
b
b
b
b
b
b
b
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
36
45
45
60
60
60
75
45
45
60
60
60
75
45
45
60
60
60
75
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3400
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
3300
3300
3300
3300
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
3700
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
2546
2946
3218
3218
2946
3218
3400
2946
3218
3400
2946
3218
3400
2946
3218
3400
2946
3218
3400
3400
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3500
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
3750
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
GROSS
AXLE
W EIGHT
R A TIN G
REAR *
3400 b
3400 b
3400 b
3400 b
3400 b
3400 b
4000 G50
3400 b
3400 b
4000 G50
3400 b
3400 b
4000 G50
3400 b
3400 b
4000 G50
4500 b
4500 b
4500 b
4500 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
5600 b
2546
2946
3218
3218
2946
3218
3582
2946
3218
3582
2946
3218
3582
2946
3218
3582
2946
3218
3582
3750
3980
4120
4700
4880
5560
5560
3980
4120
4700
4880
5560
5560
3980
4120
4700
4880
5560
5560
REQUIRED
OPTIONS
F58
AS3, F58
F58
F58
F58
F58
F58
F58
F58
A T 5, F58
F58, A T5
F58
F58
F58
F58
F58
F58
F58
F58
F58
F58
F58
F58
'R e fe r to the Gross Vehicle Weight Rating plate on the vehicle. Gross A xle Weight Rating-Front, and Gross A xle Weight Rating Rear on this chart are based upon component
m inim um capacity o f axles, springs, or tires.
b = base equipment
RESTRICTIONS
K10514 and K10514 + Z58 or Z59
RPO AS3 rear seat not available on 4900 GVWR vehicles.
K 10906 and K10906 + E55
RPO A T5 or AS3 not available on 5600 GVWR models
RPO AS3 not available on 6000 GVWR models
L78-15 and 9.50-16.5 Tires
Heavy d uty wheels are required w ith these tires, and are included when installed at the factory.
For detailed inform ation, see tire and wheel restrictions in &quot;O wner's and Driver's Manual&quot;.
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N A N D LUBRICATION
0 -9
LOAD CAPACITY CHART
GROSS
VEHICLE
1973 M O D E L S
W HEEL
BA SE
P10542
Forward Control
Chassis
102
P10542+ E32
Forward Control
w ith steel body
102
W EIGHT
RATING
(POUN DS)*
4900
5200
5600
6000
4900
5200
5600
6000
6800
P20842
P21042
Forward Control
chassis
125
133
P20842, P21042
Forward Control
+ E32 (steel body), or
+ E33 (aluminum body)
125
133
P30842, P31042, P31442
Forward Control chassis
w ith single rear
wheels
125
133
157
7500
8000
6800
7500
8000
7600
8200
9000
9000
P30842, P31042, P31442
Forward Control
chassis with
dual rear wheels
125
133
157
P30842, P31042, P31442
Forward Control + E32
(steel body), or + E33
(aluminum body), w ith
single rear wheels.
125
133
157
P30842, P31042, P31442
forward Control + E32
(steel body), or + E33
(aluminum body) w ith
dual rear wheels.
125
133
157
10000
12000
14000
7600
8200
9000
9000
10000
12000
14000
M I N I M U M M A N D A T O R Y E Q U I P M E N T F O R G VW R A T I N G
G R OS S
REAR
AXLE
TIR E
W EIGHT
PRES&shy;
FRONT
RATING
REAR
REAR
FRONT
AXLE
SURE
AXLE
S PR I N G S F R O N T *
SPRINGS
FRONT
TIR E
FRONT
TIR ES
G 7815B
G78-15B
H78-15B
L78-15B
G78-15B
G78-15B
H78-15B
L78-15B
8.75-16.5C
or 7.50-16C
8.75-16.5C
or 7.50 16C
9.50-16.5D
or 7.50-16C
8.75-16.5C
or 7.50-16C
8.75-16.5C
or 7.50-16C
9.50-16.5D
or 7.50-16C
8.75-16.5C
or 7.50-16C
9.50-16.5D
or 7.50-16C
9.50-16.5D
8.00-16.5D
or 7.50 16C
8.00-16.5D
or 7.50-16C
7.00-18D
8-19.5D
8.75-16.5C
or 7.50-16C
9.50-16.5D
or 7.50-16C
9.50-16.5D
8.00-16.5D
or 7.50-16C
8.00-16.50
or 7.50-16C
7.00-18D
8-19.5D
PRES&shy;
SURE
b
b
b
b
b
b
32
32
32
26
32
32
32
26
40
40
40
40
30
40
40
40
40
40
30
40
45
45
35
45
35
60
45
60
45
55
50
45
45
35
45
35
60
45
60
45
55
50
REAR
TIR ES
G 78 1 5B
G78-15B
H78-15B
L78-15B
G78-15B
G78-15B
H78-15B
L78 15B
8.75-16.5C
or 7.50-16C
8.75-16.5D
or 7.50-16D
9.50-16.5D
or 7.50-16E
8.75-16.5C
or 7.50-16C
8.75-16.5D
or 7.50-16D
9.50-16.5D
or 7.50-16E
8.75-16.5D
or 7.50-16D
9.50-16.5D
or 7.50-16E
9.50-16.5E
8.00 16.5D
or 7.50 16C
8 00 16.5D
or 7.50-16C
7.00-18D
8-19.5E
8.75 16.5D
or 7.50-16D
9.50-16.5D
or 7.50-16E
9.50 16.5E
8.00 16.5D
or 7.50-16C
8.00-16.5D
or 7.50-16C
7.00-18D
8-19.5E
b
b
b
b
b
b
32
32
32
32
32
32
32
32
45
45
60
60
60
75
45
45
60
60
60
75
60
60
60
75
65
60
45
60
45
65
80
60
60
60
75
65
60
45
60
45
65
80
3100 b
3100 b
3100 b
3100 b
3100 b
3100 b
3100 b
3100 b
3700 b
3700 b
3700 b
3700 b
3700 b
3700 b
3700 b
3700 b
3700 b
3700 b
3700 b
3700 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 H22
4000 H22
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 b
4000 H22
4000 H22
3100 b
3100 b
3100 b
3100 b
3100 b
3100 b
3100 b
3100 b
3600 b
3600 b
3600 b
3600 b
3600 b
3600 b
3600 b
3600 b
3600 b
3600 b
3600 b
3600 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 H22
4400 H22
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 b
4400 H22
4400 H22
2946
2946
3100
3100
2946
2946
3100
3100
3600
3600
3600
3600
3600
3600
3600
3600
3600
3600
3600
3600
3980
4000
4000
4000
4000
4000
4000
4000
4000
4000
4000
3980
4000
4000
4000
4000
4000
4000
4000
4000
4000
4000
3000 b
3500 b
3500 b
3000 b
4400 G50
3500 b
3500 b
4400 G50
3500 b
3000 b
3000 b
3500 b
4400 G50
3500 b
3500 b
4400 G50
4400 b
5700 b
5700 b
4400 b
5700 b
5700 G50
5700 G50
5700 b
5700 b
5700 G50
5700 b
5700 G50
5700 b
4400 b
4400 b
5700 b
5700 b
5700 G50
5700 G50
5700 b
5700 b
5700 G50
5700 G50
5700 b
7500 b
6200 b
7500 b
6200 b
7500 b
6200 b
7500 b
6200 b
6200 b
7500 b
6200 b
7500 R05
7500 R05
6200 b
8000 G60
7500 R05
8000 G60
7500 R05
11000 H22 11800 H22
11000 H22 11800 H22
6200 b
7500 b
6200 b
7500 b
7500 b
6200 b
6200 b
7500 b
7500 b
6200 b
6200 b
7500 R05
7500 R05
6200 b
8000 G60
7500 R05
8000 G60
7500 R05
11000 H22 11800 H22
11000 H22 11800 H22
* Refer to the Gross Vehicle Weight Rating plate on the vehicle. Gross Axle Weight Rating-Front, and Gross A xle Weight Rating-Rear on this chart are based upon component
m inim um capacity of axles, springs, or tires.
b. Base equipment.
RESTRICTIONS
L78-1 5 and 9.50-16.5 tires
Heavy d uty wheels are required w ith these tires, and are included when installed at the factory. For detailed in form ation,
see tire and wheel restrictions in &quot;O wner's and Driver's Manual&quot;.
RPO H22 rear axle
When RPO LS9 (350 V8) is used instead of the 307 V8, RPO H23 is required, replacing H22.
LIGHT DUTY TRUCK SERVICE MANUAL
GROSS
AXLE
W EIGHT
RATIN G
REAR *
2946
2946
3218
3500
2946
2946
3218
3500
3980
4120
4700
4880
5560
5560
3980
4120
4700
4880
5560
5560
4700
4880
5560
5560
6200
6200
6200
7200
7260
9080
11000
4700
4880
5560
5560
6200
6200
6200
7200
7260
9080
11000
REQUIRED
OPTIONS
J70
J70
J70
J70
J70
J70
f
/0 - 1 0
GENERAL IN F O R M A T IO N A N D LUBRIC ATIO N
LOAD CAPACITY CHART
1973 M O D E L S
W HEEL
BA SE
P30832, P31132, P31432
Forward Control M otor
Home chassis w ith
single rear wheels
125
137
158.5
P30832,P31132, P31432
Forward Control m otor
home chassis w ith
dual rear wheels.
125
137
158,5
P31432,P31832
Forward Control M otor
home chassis w ith dual
GROSS
V EHICLE
W EIGHT
R ATIN G
(POUNDS)*
GROSS
AXLE
W EIGHT
RA TIN G
REAR *
FRONT
TIRES
FRONT
T IR E
PRES&shy;
SURE
REAR
TIR ES
8.75-16 5C b
or 7.50-16C
9 50 16.5D
45
45
40
8.75 16.5D b
or 7.50-16D
9.50-16 5E
60
60
65
4300 b
4300 b
4300 b
4400 b
4400 b
4400 b
4120
4300
7500 b
7500 b
7500 b
6200 b
6200 b
8.00-16.5D
60
45
8.00-16 5D
or 7.50-16C
60
45
4300 b
4300 b
4400 b
4400 b
4090
4120
7500 R05
7500 R05
6200 b
6200 b
6200
o r 7.50-16C
10500
7.50-16D
45
7.50-16C
45
4300 b
4400 b
4300
7500 R05
6200 b
6200
11300
11800
7.50-16D
7.50-16D
50
50
7.50-16C
7.50-16D
45
50
4300 b
4300 b
4400 b
4400 b
4300
4300
7500 R05
7500 R05
7500 G50
7500 G50
7260
7500
14000
7.00-18D
or 8-19.5D
75
65
7.00-18D
or 8-19.5D
65
65
5000 HF7
5000 HF7
5000 HF7
5000 HF7
5000
5000
10000 HF7
10000 HF7
9500 HF7
9500 HF7
9080
9500
7600
9000
10100
158.5
178
MINIMUM M A N D A T O R Y EQ U IP M EN T FO R GVW R A T IN G
GROSS
REAR
AXLE
TIR E
W EIGHT
FRONT
PRES
FRONT
RATIN G
REAR
REAR
SURE
AXLE
SPRINGS F R O N T *
AXLE
SPRINGS
3980
6200 b
REQUIRED
OPTIONS
4700
4880
6200
6200
Refer to the Gross Vehicle Weight Rating plate on the vehicle. Gross A xle Weight Rating-Front, and Gross A xle Weight Rating-Rear on this chart are based upon component
m inim um capacity of axles, springs, or tires.
b. Base equipment.
RESTRICTIONS
9.50-16.5 tires
Heavy d uty wheels are required w ith these tires, and are included when installed at the factory. For detailed inform ation, see tire and wheel restrictions in
&quot;O wner's and Driver's M anual&quot;.
RPO HF7 rear axle has a 4.56-to-1 gear ratio. RPO HF8, which has a 4.88-to-1 gear ratio, may be specified in place of HF7.
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N A N D LUBR IC A TION
0-11
LO A D C A P A C ITY C H A R T
M I N I M U M M A N D A T O R Y E Q U I P M E N T F O R G VW R A T I N G
G R OS S
1973 M O D E L S
W HEEL
B ASE
VEHICLE
W EIGHT
RATIN G
(P O U N D S ) *
4500
G11005
G11305
125
G31005
G31305
110
125
E78-14B
32
b
5000
F78-14B
or 7.00- 14D
4600
F78-14B
or 7.00-14C
32
60
32
45
32
60
32
32
32
32
45
35
35
45
45
45
35
35
45
45
5100
G21305
TIRES
45
125
110
FRONT
or 7.00-14C
110
G21005
FRONT
TIR E
PRES
SURE
5500
6000
5600
6000
6200
6900
7100
7700
8100
6400
7100
7300
7900
8300
F78-14B
or 7.00-14D
G78-15B
H78-15B
G78-15B
H78-15B
8.00-16.5C
8.75-16.5C
8.75-16.5D
8.75-16.5D
8.75-16.5E
8.00-16.5C
8.75-16.5C
8.75-16.5D
8.75 16.5D
8.75-16.5E
b
b
b
b
b
TIRES
REAR
TIR E
PRES&shy;
SURE
E78-14B
b
or 7.00-14C
40
REAR
F78-14B
or 7.00 14D
F78-14B
b
or 7.00-14C
F78-14B
or 7.00-14D
G78-15B
b
H78-15B
G78-15B
b
H78-15B
8 .0 0 1 6 .5C b
8.75-16.5C
8.75-16.5D
8.75-16.5D
8.75-16.5E
8.00-16.5C b
8.75-16.5C
8.75-16.5D
8.75-16.5D
8.57-16.5E
32
32
60
32
/.0
32
60
32
32
32
32
45
45
50
60
75
45
45
50
60
75
GR OS S
AXLE
W EIGHT
RATIN G
FRONT *
REAR
AXLE
REAR
S PR I N G S
GROSS1
AXLE
W EIGHT
R A TIN G
REAR *
2546
2620
3100 b
3100 b
2300 b
2300 b
2300
2300
3100 F60
3100 F60
2620 b
2620 b
3100 F60
3100 F60
3200 b
3200 b
3200 b
2728
3000
2620
2620
3100
3100
3100
3100
3100
b
b
b
b
b
3200 G50
3200 G50
2300 b
2300 b
2728
3100
2300
2300
J70
J70
b
b
b
b
3200 b
3400 b
3400 b
3400 b
3900 F60
3900 F60
3400 b
3400 b
3400 b
3900 F60
3900 F60
3200
3400
3400
3400
3900
3900
3400
3400
3400
3900
3900
3500
5700
5700
5700
5700
5700
5700
5700
5700
5700
5700
b
b
b
b
b
b
b
b
b
b
b
3200 G50
3200 G50
3200 b
3200 b
3200 b
3200 b
2728
3100
2946
3200
2946
3200
J70
3100
3500
3500
3500
4200 b
4200 b
4200 b
5500 G50
5500 G50
4200 b
4200 b
4200 b
5500 G50
5500 G50
3460
3980
4200
4700
5360
3460
3980
4200
4700
5360
FRONT
AXLE
FRONT
S PR I N G S
3000 b
3000 b
2620 b
3000
3000
3000
3000
3000
3000
3200
3200
3200
3200
3900
3900
3900
3900
3900
3900
3900
3900
3900
3900
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
2620 b
2728
3000
2946
3200
2946
REQUIRED
OPTIONS
J70
LS9, F59
LS9, F59
LO AD C A P A C IT Y C H A R T
1973 M O D E L S
G 11006, and
G 11006+ E94
G11306, and
G11306 + E94
G21006, and
G21006 + E94
G21306, and
G21306 + E94
G31306, and
G 3 1 3 0 6 + E94
W HEEL
B A SE
GROSS
VEHICLE
W EIGHT
RATIN G
(POUN DS)*
FRONT
TIR E
PRES&shy;
SURE
FRONT
TIR ES
REAR
TIR ES
3000 b
3100 b
2946
3100 b
3200 b
2946
32
32
32
32
3200
3200
3200
3200
3900
3900
3900
3900
3900
3200 b
3200 b
3200 b
3200 b
3400 b
3400 b
3400 b
3900 F60
3900 F60
2946
3200
2946
3500 b
3500 b
3500 b
3200 b
3200 b
3200 b
3200
3400
3400
3500 b
5700 b
5700 b
5700 b
5700 b
5700 b
3200 b
4200 b
4200 b
4200 b
5500 G50
5500 G50
2946
3200
2946
3200
32
45
35
35
45
45
H78-15B
8.00-16.5C
8.75-16.5C
8.75-16.5D
8.75-16.5D
8.75-16.5E
5400
G78-14B
b
32
5700
G78 15B
H78-15B
b
32
G 78 1 5B
H78-15B
8.00-16.5C
8.75-16.5C
b
8.75-16.5D
8.75-16.5D
8.75-16.5E
32
32
32
125
7800
8300
2728
2946
b
F78-14B
G78-14B
125
3200 b
3200 b
b
32
32
7100
7300
3100 b
3100 b
G78-15B
H78 15B
G78-15B
b
b
2728
2946
G78-14B
F78-14B
G78-14B
125
3100 b
3100 b
32
32
5200
5400
b
b
GROSS
AXLE
W EIGHT
RATING
REAR *
3000 b
3000 b
b
110
6000
5800
6200
6600
MINIM UM M A N D A T O R Y E Q U I P M EN T F O R GVW R A T IN G
G RO S S
AXLE
REAR
W EIGHT
TIR E
REAR
REAR
FRONT
RATIN G
PRES
FRONT
AXLE
SPRINGS
AXLE
SPRINGS F R O N T *
SURE
45
45
50
60
75
b
b
b
b
b
b
b
b
b
3400
3900
3900
3460
3980
4200
4700
5360
REQUIRED
OPTIONS
LS9, F59
' Refer to the Gross Vehicle Rating plate on the vehicle. Gross Axle Weight Rating-Front, and Gross Axle Weight Rating-Rear on this chart are based upon component
minim um capacity of axles, springs, or tires.
b = base equipment.
RESTRICTIONS
G 11006 and G11006 + E94
RPO C62, C63 not available on 5200 GVWR models.
G 11306+ E94
RPO C62, C63 not available.
G21006 + E94
RPO C62, C63 not available on 5700 GVWR models having RPO AQ3.
G21306 and G21306 + E94
RPO C62, C63 not available on 5800 GVWR models.
RPO AQ3 not available on 5800 GVWR models.
G21306
RPO C62, C63 not available on 5800 GVWR models w ith AQ3.
G31306 and G31306 + E94
RPO AQ4 not available on 6600 GVWR models,
7800 and 8300 GVWR models, and RPO F60 (heavy duty fro n t springs), and RPO G50 (heavy d uty rear springs) are not recommended fo r normal passenger use
LIGHT DUTY TRUCK SERVICE MANUAL
0 -1 2 GENERAL IN F O R M A T IO N A N D LUBRIC ATIO N
LUBRICATION
INDEX
Maintenance Schedule........................................................
E ngine.....................................................................................
Oil and Filter Recommendations................................
Drive Belts...........................................................................
Positive Crankcase V entilation.....................................
Air Injection Reactor System .......................................
Controlled Combustion System ....................................
GM Evaporation Control System................................
Manifold Heat Control V alve......................................
Air Cleaner..........................................................................
Fuel Filter............................................................................
Distributor............................................................................
G overnor..............................................................................
Accelerator Linkage..........................................................
Automatic Transmission Fluid Recommendations...
Manual Transmission.........................................................
Transmission Shift Linkage............................................
Clutch......................................................................................
Rear Axle
S tandard...............................................................................
Positraction..........................................................................
Propeller Shaft Slip Joints..............................................
Universal Joints...................................................................
0-12 Wheel Bearings
0-12 Front.......................................................................................
0-12 R ear........................................................................................
0-13 Brake Master Cylinder......................................................
0-13 Brake and Clutch Pedal Springs...................................
0-13 Parking Brake.......................................................................
0-13 Steering
0-13 Manual Steering G ear.....................................................
0-13 Steering Linkage and Suspension................................
0-14 Hood Latch and Hood H inge........................................
0-14 Body Lubrication..................................................................
0-14 Four Wheel Drive
0-14 Propeller Shaft Centering Ball.....................................
0-14 Front A xle...........................................................................
0-14 Air Vent H ose....................................................................
0-14 Transfer Case......................................................................
0-14 Control Lever and Linkage...........................................
0-14 Speedometer A dapter.........................................................
0-15
0-15
0-15
0-15
MAINTENANCE SCHEDULE
&raquo;&gt;
A separate maintenance folder has been provided with
each car which contains a complete schedule and brief
explanation of the safety, emission control, lubrication
and general maintenance it requires. The maintenance
folder information is supplemented by this section of
this manual, as well as the separate emission control
systems folder also furnished with each car. Read all
three publications for a full understanding of vehicle
maintenance requirements.
The time or mileage intervals for lubrication and
maintenance services outlined in this section are
intended as a general guide for establishing regular
maintenance and lubrication periods. Sustained heavy
duty and high speed operation or operation under
adverse conditions may require more frequent servicing.
ENGINE
0-15
0-15
0-15
0-15
0-15
0-15
0-16
0-16
0-16
0-17
0-17
0-17
0-17
0-17
0-17
Lubrication Diagrams
Conventional and Forward Control Models............ 0-18
Four Wheel Drive M odels............................................. 0-19
1/2, 3/4 and 1 ton G Models..................................... 0-20
than 6,000 miles are driven in a 4-month period,
change oil each 6,000 miles.
• Change oil each 2 months or 3,000 miles, whichever
occurs first, under the following conditions:
—Driving in dusty conditions
—Trailer pulling or camper use.
—Frequent long runs at high speeds and high
ambient temperatures.
—Motor Home use.
—Stop and go type service such as delivery trucks,
etc.
—Extensive idling
—Short-trip operation at freezing temperatures
(engine not thoroughly warmed-up).
Oil &amp; Filter Recommendations
The letter designation &quot;SE&quot; has been established to
correspond with the requirements of GM 6136-M. &quot;SE&quot;
engine oils will be better quality and perform better than
those identified with &quot;SA&quot; through &quot;SD &quot; designations
and are recommended for all light-duty gasoline trucks
regardless of model year and previous engine oil quality
recommendations.
Oil Change Period
• Use only SE engine oil.
• Change oil each 4 months or 6,000 miles. If more
• Operation in dust storms may require an immediate
oil change.
• Replace the oil filter at the first oil change, and
every second oil change thereafter. AC oil filters
provide excellent engine protection.
The above recommendations apply to the first
change as well as subsequent oil changes. The oil
change interval for the engine is based on the use of
SE oils and quality oil filters. Oil change intervals
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N AND LU BRICATION
longer than those listed above will seriously reduce
engine life and may affect the m anufacturer’s
obligation under the provisions of the New Vehicle
W arranty.
A high quality SE oil was installed in the engine at
the factory. It is not necessary to change this
factory-installed oil prior to the recommended
normal change period. However, check the oil level
more frequently during the break-in period since
higher oil consumption is normal until the piston
rings become seated.
NOTE: Non-detergent and other low quality
oils are specifically not recommended.
Oil Filter Type and Capacity
• Throwaway type, l quart U.S. measure, .75 quart
Imperial measure.
• 250 cu. in., 292 cu. in., AC Type PF-25. 307 cu. in.,
350 cu. in. 454 cu. in., AC Type PF-35.
Crankcase Capacity (Does Not Include Filter)
• 292 L6 Engine; 5 quarts U.S. measure, 4.25 quarts
Imperial measure.
• All other engines; 4 quarts U.S. measure, 3.25 quarts
Imperial measure.
Recommended Viscosity
Select the proper oil viscosity from the following chart:
0 -1 3
mark on the dipstick, oil should be added as necessary.
The oil level should be maintained in the safety margin,
neither going above the &quot;FU LL&quot; line nor below &quot;ADD
OIL&quot; line.
NOTE: The oil gauge rod is also marked
&quot;Use SE Engine Oil&quot; as a reminder to use
only SE oils.
Supplemental Engine Oil Additives
The regular use of supplemental additives is specifically
not recommended and will increase operating costs.
However, supplemental additives are available that can
effectively and economically solve certain specific
problems without causing other difficulties. For example,
if higher detergency is required to reduce varnish and
sludge deposits resulting from some unusual operational
difficulty, a thoroughly tested and approved additive &quot;Super Engine Oil Supplement&quot;- is available.
Drive Belts
Drive belts should be checked every 6,000 miles or 4
months for proper tension. A loose belt will affect water
pump and generator operation.
POSITIVE CRANKCASE VENTILATION
VALVE
Every 24,000 miles or 24 months the valve should be
replaced. Connecting hoses, fittings and flame arrestor
should be cleaned. At every oil change the system should
be tested for proper function and serviced, if necessary.
RECOMMENDED SAE VISCOSITY NUMBER
AIR INJECTION REACTOR SYSTEM (A.I.R.)
CONTROLLED COMBUSTION SYSTEM
(C.C.S.)
10W , 5W -3 0 , I0 W -3 0 , 10W -40
r
.3 0
i
i
i
i
i— i
-2 0
0
20
40
60
80
TEMPERATURE RANGE ANTICIPATED BEFORE NEXT OIL CHANGE, &deg;F.
100
NOTE: SAE 5W-20 oils are not recom&shy;
mended for sustained high-speed driving.
SAE 30 oils may be used at temperatures
above 40&deg;F. SAE 5W-30 oils are recom&shy;
mended for all seasons in vehicles normally
operated in Canada.
The proper oil viscosity helps assure good cold and hot
starting.
Checking Oil Level
The engine oil should be maintained at proper level. The
best time to check it is before operating the engine or as
the last step in a fuel stop. This will allow the oil
accumulation in the engine to drain back in the
crankcase. To check the level, remove the oil gauge rod
(dip stick), wipe it clean and reinsert it firmly for an
accurate reading. The oil gauge rod is marked &quot;FU LL&quot;
and &quot;ADD OIL&quot;. If the oil is at or below the &quot;A DD &quot;
The Air Injection Reactor system should have the drive
belt inspected for wear and tension every 12 months or
12,000 miles, whichever occurs first. In addition,
complete effectiveness of either system, as well as full
power and performance, depends upon idle speed,
ignition timing, and idle fuel mixture being set
according to specification. A quality tune-up which
includes these adjustm ents should be perform ed
periodically to assure normal engine efficiency, operation
and performance.
GM EVAPORATION CONTROL SYSTEM
Every 24 months or 24,000 miles (more often under
dusty conditions) the filter in the base of the canister
must be replaced and the canister inspected.
MANIFOLD HEAT CONTROL VALVE
Every 6,000 miles or 4 months, check valve for freedom
of operation. If valve shaft is sticking, free it up with
GM Manifold Heat Control Solvent or its equivalent.
LIGHT DUTY TRUCK SERVICE MANUAL
0 - 1 4 GENERAL IN F O R M A T IO N A N D LUBRICATIO N
AIR CLEANER
CAUTION: Do not remove the engine air
cleaner unless temporary removal is necessary
during repair or maintenance of the vehicle.
When the air cleaner is removed backfiring can
cause fire in the engine compartment.
NOTE: Under prolonged dusty driving
conditions, it is recommended that these
operations be performed more often.
011 Wetted Paper Element Type
L-6 engine, replace every 12,000 miles. V-8 engine, every
12,000 miles inspect element for dust leaks, holes or
other damage. Replace if necessary. If satisfactory,
rotate element 180&deg; from originally installed position.
Replace at 24,000 miles. Element must not be washed,
oiled, tapped or cleaned with an air hose.
Crankcase Ventilation Filter
(Located Within Air Cleaner)
If so equipped, inspect every oil change and replace if
necessary. Replace at least every 24,000 miles; more
often under dusty driving conditions.
FUEL FILTER
Replace filter element located in carburetor inlet every
12 months or 12,000 miles whichever occurs first, or, if
an in-line filter is also used, every 24,000 miles. Replace
in-line filter every 24,000 miles.
DISTRIBUTOR
Replace cam lubricator at 24,000 mile intervals.
GOVERNOR
The attaching bolts should be kept tight, the optionally
available governor should be kept clean externally and
the filter element should be replaced every 12,000 miles.
ACCELERATOR LINKAGE
Lubricate with engine oil every 12,000 miles as follows:
1. On V8 engine, lubricate the ball stud at the
carburetor lever.
2. On L6 engine, lubricate the two ball studs at the
carburetor lever and lubricate the lever mounting
stud. Do not lubricate the accelerator cable.
AUTOMATIC TRANSMISSION
FLUID RECOMMENDATION
Use only automatic transmission fluids identified with
the mark DEXRON (or equivalent). These fluids have
been specially formulated and tested for use in the
automatic transmission.
Check the fluid level at each engine oil change period.
To make an accurate fluid level check:
1. Drive vehicle several miles, making frequent starts
and stops, to bring transmission up to normal
operating temperature (approximately 180-190&deg;F).
2. Park vehicle on a level surface.
3. Place selector lever in &quot;Park&quot; and leave engine
running.
4. Remove dipstick and wipe clean.
5. Reinsert dipstick until cap seats.
6. Remove dipstick and note reading.
If oil level is at or below the ADD mark on the dipstick,
oil should be added as necessary. One pint raises the
level from ADD to FULL. Do not overfill.
Under normal driving conditions, the transmission fluid
should be changed every 24,000 miles. If the vehicle is
driven extensively in heavy city traffic during hot
weather, or is used to pull a trailer, change fluid every
12,000 miles. Likewise, operators of trucks in commercial
use where the engine idles for long periods, should
change fluid every 12,000 miles.
To Change Turbo Hydra-Matic 400 and Turbo HydraMatic 350 fluid,
remove fluid from the transmission
sump, add approximately 7.5 pints U.S. measure (6.25
pints Imperial measure) for the Turbo Hydra-Matic 400
and 2 1/2 qts. U.S. measure (2 qts. Imperial measure) for
the Turbo Hydra-Matic 350 of fresh fluid, to return level
to proper mark on the dipstick.
Every 24,0 00 Miles—the Turbo Hydra-M atic 400
transmission sump filter should be replaced.
3-AND 4-SPEED MANUAL TRANSMISSION
LUBRICANT
Every 4 months or 6,000 miles, whichever occurs first,
check lubricant level and add lubricant, if necessary, to
fill to level of filler plug hole with SAE 80 or SAE 90 GL5 Gear Lubricant. If temperatures below + 32&deg;F are
expected, use SAE 80 GL-5 Gear Lubricant only.
For those vehicles normally operated in Canada, use
SAE 80 GL-5 Gear Lubricant.
TRANSMISSION SHIFT LINKAGE
(MANUAL AND AUTOMATIC)
Every 6,000 miles or 4 months-lubricate shift linkage
and, on Manual transmission floor control, lever
contacting faces with water resistant EP chassis lubricant
which meets General Motors Specification GM6031-M.
Clutch
The clutch pedal free travel should be checked at regular
intervals.
Lubricate the clutch cross-shaft at fitting (on Series 10
Forward Control models also lubricate the clutch linkage
idler lever at fitting) every 6,000 miles or 4 months with
water resistant EP chassis lubricant which meets General
Motors Specification GM 6031-M.
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N A ND L UBRICATION
REAR AXLES
Standard
Every 4 months or 6,000 miles, whichever occurs first,
check lubricant level and add lubricant, if necessary, to
fill to level of filler plug hole. Use GL-5 G ear Lubricant
as shown in the following table. (For vehicles normally
operated in Canada, use SAE 80 GL-5 G ear Lubricant.)
0 -1 5
The bearings should be thoroughly cleaned before
repacking with lubricant.
Front wheels are equipped with tapered roller bearings
on all trucks. Wheel bearings should be lubricated every
24.000 miles. Do not mix wheel bearing lubricants.
CAUTION: &quot; Long fibre&quot; type greases should
not be used on roller bearing front wheels.
Rear
O u tsid e T e m p e ra tu re
BELOW
10&deg;F
Viscosity Lu b ric a n t T o Be Used
SAE 80
UP TO 100&deg;F
SAE 90
ABOVE 100&deg;F
C ONSISTENTLY
SAE 140
On 20 or 30 Series trucks, drain lubricant every 24,000
miles. If vehicle is operated in exceptionally heavy work
or at continuous high speeds, the lubricant should be
changed every 12,000 miles. It may be necessary to
change lubricant more often if vehicle is used off road in
dusty areas.
Positraction
Drain and refill at first 12,000 miles then maintain same
as standard axle but use only the special Positractign
lubricant available at your authorized dealer.
PROPELLER SHAFT SLIP JOINTS
Propeller shaft slip joints should be lubricated every
6,000 miles or 4 months with water resistant EP chassis
lubricant which meets General Motors Specification GM
6031-M.
UNIVERSAL JOINTS
All universal joints are the needle bearing type.
Lubricate those universal joints (depending on truck
model) equipped with lube fittings every 6,000 miles or 4
months with water resistant EP chassis lubricant which
meets General Motors Specification GM 6031-M. More
frequent lubes may be required on heavy duty or &quot;Off
the Road&quot; operations.
WHEEL BEARINGS
Front
NOTE: Use wheel bearing lubricant GM
Part No. 1051344 or equivalent. This is a
premium high melting point lubricant which
meets all requirements of General Motors
Specification GM 6031-M.
Due to the weight of the tire and wheel assembly it is
recommended that they be removed from hub before
lubricating bearings to prevent damage to oil seal. Then
remove the front wheel hub to lubricate the bearings.
The rear wheel bearings receive their lubrication from
the rear axle. When installing bearings which have been
cleaned, prelube with wheel bearing grease.
BRAKE MASTER CYLINDER
Check master cylinder fluid level in both reservoirs every
6.000 miles or 4 months. If the fluid is low in the
reservoir, it should be filled to a point about 1/4&quot; from
the top rear of each reservoir with Delco Supreme No.
11 or D.O.T.-3 Hydraulic Brake Fluid or equivalent.
BRAKE AND CLUTCH PEDAL SPRINGS
Lubricate brake and clutch pedal springs every 6,000
miles or 4 months with engine oil for all models.
PARKING BRAKE
Every 6,000 miles or 4 months clean and lubricate all
parking brake pivot points with water resistant EP
chassis lubricant which meets General Motors Specifica&shy;
tion GM 6031-M.
STEERING
Manual Steering Gear
The steering gear is factory-filled with steering gear
lubricant. Seasonal change of this lubricant should not
be performed and the housing should not be drained-no
lubrication is required for the life of the steering gear.
Every 36,000 miles, the gear should be inspected for seal
leakage (actual solid grease-not just oily film). If a seal is
replaced or the gear is overhauled, the gear housing
should be refilled with No. 1051052 (13 oz. container)
Steering Gear Lubricant which meets GM Specification
GM 4673-M, or its equivalent.
NOTE: Do not use EP Chassis Lube, which
meets GM Specification GM 6031-M, to
lubricate the gear. DO NOT OVER-FILL the
gear housing.
NOTE: Lubricate intermediate steering shaft
with water resistant EP chassis lubricant
which meets General Motors Specification
GM 6031-M every 6,000 miles or 4 months
on P-10 models only.
Power Steering System
Check the fluid level in the pump reservoir at each oil
change period. Add GM Power Steering Fluid or
LIGHT DUTY TRUCK SERVICE MANUAL
0 - 1 6 GENERAL IN F O R M A T IO N A N D LUBRICATIO N
DEXRON automatic Transmission Fluid or equivalent as
necessary to bring level into proper range on filler cap
indicator depending upon fluid temperature.
2. Apply Lubriplate or equivalent to latch pilot bolt
and latch locking plate.
3. Apply light engine oil to all pivot points in release
mechanism, as well as prim ary and secondary latch
mechanisms.
4. Lubricate hood hinges.
5. Make hood hinge and latch mechanism functional
check to assure the assembly is working correctly.
BODY LUBRICATION
If at operating temperature (approximately 150&deg;F—hot to
the touch), fluid should be between &quot;HOT&quot; and
&quot;COLD&quot; marks.
If at room temperature (approximately 70&deg;F), fluid
should be between &quot;A DD &quot; and &quot;COLD&quot; marks. Fluid
does not require periodic changing.
STEERING LINKAGE AND SUSPENSION
M aintain correct front end alignment to provide easy
steering, longer tire life, and driving stability.
Check control arm bushings and ball joints for wear.
Lubricate tie rods, upper and lower control arms, and
ball joints at fittings with water resistant EP chassis
lubricant which meets General Motors Specification GM
6031-M every 6,000 miles or 4 months.
Lubricate every 3,000 miles or 2 months whichever
occurs first under the following conditions:
• Driving in dusty or muddy conditions.
• Extensive ofF-road use.
NOTE: Ball joints must be at + 10&deg;F. or
more before lubricating.
Keep spring to axle U bolts and shackle bolts properly
tightened (see Specifications Section for torque recom&shy;
mendations). Check U bolt nuts after the first 1,000 miles
of operation if the U bolt or U bolt nuts are changed in
service.
HOOD LATCH AND HOOD HINGE
Every 6,000 miles or 4 months, whichever occurs first,
lubricate hood latch assembly and hood hinge assembly
as follows:
1. Wipe off any accumulation of dirt or contamination
on latch parts.
Normal use of a truck causes metal-to-metal movement
at certain points in the cab or body. Noise, wear and
improper operation at these points will result when a
protective film of lubricant is not provided.
For exposed surfaces, such as door checks, door lock
bolts, lock striker plates, dovetail bumper wedges, etc.,
apply a thin film of light engine oil.
Where oil holes are provided in body parts a dripless oil
can be safely used, but any lubricant should be used
sparingly, and after application all excess should be
carefully wiped off.
The seat adjusters and seat track, ordinarily overlooked,
should be lubricated with water resistant EP chassis
lubricant which meets General Motors Specification GM
6031-M.
There are other points on bodies which may occasionally
require lubrication and which are difficult to service.
Window regulators and controls are confined in the
space between the upholstery and the outside door panel.
Easy access to the working parts may be made by
removing the trim. Door weatherstrips and rubber hood
bumpers should be lightly coated with a rubber
lubricant.
UNDERBODY MAINTENANCE
The effects of salt and other corrosive materials used for
ice and snow removal and dust control can result in
accelerated rusting and deterioration of underbody
components such as brake and fuel lines, frame,
underbody floor pan, exhaust system, brackets, parking
brake cables. These corrosive effects, however, can be
reduced by periodic flushing of the underbody with plain
water. In geographic areas having a heavy concentration
of such corrosive materials, it is recommended that the
complete underbody be inspected and flushed at least
once a year, preferably after a winter’s exposure.
Particular attention should be given to cleaning out
underbody members where dirt and other foreign
materials may have collected.
FOUR WHEEL DRIVE
Most lubrication recommendations and procedures for 4
wheel drive-equipped trucks are the same for corre&shy;
sponding components of conventional drive trucks.
In addition, the following items require lubrication at the
intervals mentioned.
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N A ND LUBRIC ATIO N
0 -1 7
Conventional Four Wheel Drive
Propeller Shaft Centering Ball
A centering ball at the transfer case end of the front
propeller shaft on Four Wheel Drive Models should be
lubricated every 24,000 miles with water resistant EP
chassis lubricant which meets General Motors Specifica&shy;
tion GM 6031-M. More frequent lubrication may be
required on heavy duty off the road operations.
NOTE: A special needle nose grease gun
adapter for flush type grease fitting is
required to lubricate the centering ball.
Front Axle
The front axle should be checked every 6,000 miles or 4
months and refilled with SAE 90 GL-5 Gear Lubricant
when necessary. With the differential at operating
temperature, fill to the level of filler plug hole. If
differential is cold, fill to level of 1/2&quot; below the filler
plug hole. For vehicles normally operated in Canada use
SAE 80 GL-5 Gear Lubricant.
Add SAE 80 or SAE 90 GL-5 Gear Lubricant to bring to
level of filler plug hole.
Full Time Four Wheel Drive
Add engine oil to bring to level 1/2&quot; below filler plug
hole.
Control Lever and Linkage
Since no grease fitting is provided in the control lever it
is necessary to brush or spray engine oil on the lever
pivot point and on all exposed control linkage every
6,000 miles or 4 months.
SPEEDOMETER ADAPTER
On vehicles so equipped, lubricate adapter at fitting with
water resistant EP chassis grease which meets General
Motors Specification GM 6031-M every 6,000 miles.
Air Vent Hoses
Check vent hose at front axle and at transfer case for
kinks and proper installation every 6,000 miles or 4
months.
Transfer Case
Check the transfer case level every 6,000 miles or 4
months and, if necessary, add lubricant as follows:
DRIVE O N HOIST
BUMPER JACK LIFTING
FLOOR JACK OR HOIST LIFT
Fig. 7—G Model Lifting Points
LIGHT DUTY TRUCK SERVICE MANUAL
0 -1 8 GENERAL IN F O R M A T IO N A N D LUBRIC ATIO N
Fig. 8—Lubrication—Conventional Models
Lubrication
Period
No.
Lubrication Points
1
2
3
b
6
/
Lower Control Arms
Upper Control Arms
Upper and Lower Control
Arm Ball Joints
Intermediate Steering
Shaft (PA10)
Tie Rod Ends
Wheel Bearings
Steering Gear
6,000 Miles
30,000 Miles
36,000 Miles
8
A ir Cleaner — Element
12,000 Miles
9
10
11
D istributor — L-6
D istributor — V-8
Master Cylinder
12,000 Miles
12,000 Miles
6,000 Miles
12
Transmission — Manual
— Autom atic
T hrottle Bell Crank — L-6
Carburetor Linkage — V-8
Brake and Clutch Pedal
Springs
Universal Joints
Propeller Shaft Slip Joint
Rear Axle
4
13
14
15
16
17
18
Type of
Lubrication
Quantity
Remarks
6,000 Miles
6,000 Miles
6,000 Miles
Chassis Lubricant
Chassis Lubricant
Chassis Lubricant
4 places as required
4 places as required
4 places as required
6,000 Miles
Chassis Lubricant
2 places as required
Chassis Lubricant
Whl. Brq. Lubricant
4 places as required
2 places as required
6.000
6.000
6,000
6,000
6,000
Miles
Miles
Miles
Miles
Miles
6,000 Miles
6,000 Miles
6,000 Miles
Delco Supreme
No. 11 or equivalent
GL-5
Dexron or equivalent
Enqine Oil
Enqine Oil
Engine Oil
As required
As
As
As
As
As
Chassis Lubricant
Chassis Lubricant
GL-5
As required
As required
As required
required
required
required
required
required
Check fo r Grease Leak—
Do not Lubricate
Replace L-6. Rotate V-8
Replace V-8 at 24.000 miles.
Replace cam lubricator*
Replace cam lubricator*
Check — add fluid
when necessary
Keep even w /fille r plug.
See Lubrication Section
Not shown
Check
See Lubrication section
* Replace Points and Lubricator at 24,000 mile intervals.
LIGHT DUTY TRUCK SERVICE MANUAL
GENERAL IN F O R M A T IO N A N D LUBRICATION
0 -1 9
Fig. 9—Lubrication—Four Wheel Drive Models
No.
Lubrication Points
Lubrication
Period
1
A ir Cleaner
12,000 Miles
2
Distributor — L-6
12,000 Miles
3
Distributor — V-8
12,000 Miles
4
Control Linkage Points
7
8
Tie Rod Ends
Wheel Bearings
6,000 Miles
30,000 Miles
9
Steering Gear
36,000 Miles
10
Master Cylinder
6,000 Miles
11
Transmission — Manual
— Autom atic
Carburetor Linkaqe — V-8
Universal Joints
Propeller Shaft Slip Joints
Front and Rear Axle
6.000
6.000
6,000
6,000
6,000
6,000
21
Drag Link
Brake and Clutch
Pedal Sprinqs
Transfer Case
22
T hrottle Bell Crank — L-6
12
13
14
15
17
18
6,000 Miles
Type of
Lubrication
Engine Oil
As required
Chassis Lubricant
Wheel Bearing
Grease
2 places as required
2 places as required
As required
Delco Supreme No.
11 or equivalent
GL-5
Dexron or equivalent
Enqine Oil
Chassis Lubricant
Chassis Lubricant
G L-6
As required
As required
As required
As required
3 places as required
As required
6,000 Miles
Chassis B
2 places as required
6,000 Miles
6,000 Miles
Enqine Oil
GL-5
As required
As required
6,000 Miles
Engine Oil
As required
Miles
Miles
Miles
Miles
Miles
Miles
Remarks
Quantity
Replace L-6. Rotate V-8.
Replace V-8 at 24,000
miles.
Replace Cam
Lubricator*
Replace Cam
Lubricator*
Brush or Spray
to apply
Check fo r Grease Leak
Do not Lubricate
Check — add fluid
when necessary
Keep even w /fille r plug
See Lubrication Section
See Lubrication Section
Check
See Lubrication Section
Check
See Lubrication Section
* Replace Points and Lubricator at 24,000 mile intervals.
LIGHT DUTY TRUCK SERVICE MANUAL
0 -2 0 GENERAL IN F O R M A T IO N A N D LUBRIC ATIO N
Fig. 10—Lubrication—1/2, 3/4 and 1 Ton G Models
No.
1
Lubrication Points
Lubrication
Period
Type of
Lubrication
8
9
Control Arm Bushings and
Ball Joints
Tie Rod Ends
Wheel Bearings
Steering Gear
Clutch Cross-Shaft
Trans. Control Shaft
A ir Cleaner—Element
6,000
6,000
30,000
36,000
6,000
6,000
12,000
10
D istributor—L-6, V-8
12,000 Miles
11
12
13
T ransmission—Synchromesh
—A utom atic
Rear Axle
Oil Filter
GL-5
Dexron or Equivalent
GL-5
14
Battery
6.000 Miles
6.000 Miles
6,000 Miles
Every Second
Oil Change
5,000 Miles
15
Brake Master Cylinder
6,000 Miles
16
Parking Brake Linkage
6,000 Miles
Delco Supreme
No. 11 or Equivalent
Chassis Lubricant
2
4
b
Miles
Miles
Miles
Miles
Miles
Miles
Miles
Q uantity
Chassis Lubricant
Chassis Lubricant
Whl. Brq. Lubricant
12 places as required
4 places as required
2 places as required
Chassis Lubricant
Chassis Lubricant
As required
As required
As required
As required
As required
Engine Oil
As required
Remarks
2 fittinqs each side
Replace L-6, Rotate
V-8, Replace V-8 at
24.000 Miles.
Replace Cam
Lubricator*
See Lubrication Section
See Lubrication Section
See Lubrication Section
Oil Terminals and
Felt Washers
Check—Add fluid when
necessary
Lubricate Linkage
and Cables
* Replace Points and Lubricator at 24,000 Mile Intervals.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-1
SECTION 1A
HEATER AND AIR CONDITIONING
CONTENTS OF THIS SECTION
Standard H eater.............................................................................. 1A-1
Auxiliary H eater.............................................................................. 1A-14
Air C onditioning............................................................................. 1A-18
STANDARD HEATER
INDEX
General Description........................................................
Theory of Operation.......................................................
System Components.......................................................
System Controls...............................................................
Component Replacement and R ep air......................
Blower M otor...................................................................
Heater Distributor and Core Assembly.................
Heater Hoses....................................................................
1A-1
1A-3
1A-3
1A-3
1A-4
1A-4
1A-4
1A-5
Center Distributor Duct - G M odels.....................
Left Distributor Duct - G M odels.........................
Defroster D uct................................................................
Control Assembly...........................................................
Control Cables.................................................................
Blower Switch...................................................................
Resistor U nit....................................................................
Diagnosis.............................................................................
1A-5
1A-6
1A-6
1A-7
1A-7
1A-9
1A-9
1A-10
GENERAL DESCRIPTION
Heating components are attached to the dash panel on
the right side of the vehicle. The blower and air inlet
assembly and water hoses are located on the forward
side of the dash panel while the heater core and
distributor duct are on the passenger side.
The heater system is an air mix type system in which
outside air is heated and then mixed in varying amounts
with cooler outside air to attain the desired air
temperature. The system consists basically of three parts:
(1) the blower and air inlet assembly, (2) the heater
distributor assembly and (3) the heater control assembly.
Fig. 1A--Heater A ir Flow Schematic G Models
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A
DEFROSTER ASM
(H E AT E R IN OFF P O S I T I O N )
1 A- 2 HEATER
H EA TE R A D E F R O S T E R A S M
AND
AIR
AI R OU T L E T
VI EW A
S T E E RI N G
COLUMN
VI EW B
DEFROSTER DUCT ASM
B L O W E R A AIR
I NLE T A SM
VIEW
B
LIGHT
AI R F L O W L E G E N D
DUTY
TRUCK
H E A T ER A S M
SERVICE
C-K MODELS
MANUAL
Fig. 1B--Heater A ir F lo w Schematic C -K Models
CONDITIO NING
AIR OUTLET
HEATER A N D AIR C O N D IT IO N IN G
1A-3
THEORY OF OPERATION
BLOWER AND AIR INLET ASSEMBLY
The blower and air inlet assembly draws outside air
through the outside air inlet grille located forward of the
windshield reveal molding and channels the air into the
heater distributor assembly. The operation of the blower
motor is controlled by the FAN switch on the heater
control. The motor is connected in series with the FAN
switch and also the blower resistor assembly. Located in
the fuse block, in series between the blower motor and
the battery, is a 25 amp. fuse C-K models - a 20 amp
fuse on G models.
TURE door in the heater distributor assembly. All
incoming &quot;outside&quot; air is directed around the heater core
in the COLD position or through the core in the HOT
position. The desired outlet temperature is obtained by
blending the heated and unheated air according to the
setting of the temperature lever.
Heater-Def Lever
The heater distributor assembly houses the heater core
and the doors necessary to control mixing and
channeling of the air. Since the unit has no water valve,
water circulation keeps the core hot at all times. That
portion of the air passing through the core receives
maximum heat from the core. Air entering the
distributor assembly is channeled as follows:
The HEATER-DEF lever controls the position of the
DEFROSTER door and the PURGE door. In the OFF
position, the blower is &quot;on&quot; and incoming air is directed
up under the dash through the purge door opening. As
the lever is moved to the right of the OFF position, the
door closes, directing airflow on into the distributor
assembly. With the lever at HEATER, the DEFROSTER
door directs almost all airflow to the heater (floor) outlets
- a small amount of air is directed to the defroster (dash)
outlets. In the DEF position, most airflow is diverted to
the defroster outlets. Moving the lever part way, as
desired, will split airflow between the floor and defroster
outlets.
C-K Models
Fan Control
HEATER DISTRIBUTOR ASSEMBLY
Air entering the distributor can be directed out the purge
door opening, on the right end of the distributor
assembly, by the purge door. If the purge door is closed,
then air is directed through and/or around the heater
core by the temperature door. Air is then directed into
the passenger compartment through the heater (floor)
outlets and/or the defroster (dash) outlets by the
defroster door. The temperature of the outlet air is
dependent on the ratio of heated to unheated air
(controlled by the temperature door).
The blower fan lever is located at the left hand side of
the control assembly. The blower motor will operate as
soon as the ignition switch is turned to the RUN
position. The control has three positions only; LO, MED,
HI. There is no OFF position.
G Models (Fig. 3)
The controls are located in the instrument panel, just to
the right of the instrument cluster. In operation, two
levers control all heating operations.
G Models
Airflow is controlled by three doors in the distributor
assembly. The air door can be adjusted to vary airflow. If
air is allowed to enter the distributor assembly, it is then
directed through and/or around the heater core by the
temperature door. Air is directed into the passenger
compartment through the heater (floor) and/or defroster
(dash) outlets by the defroster door. The temperature of
the outlet air is dependent on the ratio of heated to
unheated air (controlled by the temperature door).
—
Hl
-
I - ■
.
HOI
C01D
j f
~
DEF
_ ■j
HEATER
■
OFF
\
&lt;
10
n
, j
-
FAN
Fig. 2-Heater Control--C-K Models
CONTROLS
C-K Models (Fig. 2)
These controls are mounted in the center of the dash,
above the radio assembly. The control incorporates two
levers which make use of bowden cables to control
positioning of the purge, temperature and defroster
doors.
Temperature Lever
This lever controls the positioning of the TEMPERA-
Fig. 3-Heater Control-G Models
LIGHT DUTY TRUCK SERVICE MANUAL
1 A-4 HEATER A N D AIR C O N D IT IO N IN G
Temperature Lever
This lever controls the positioning of the TEMPERA&shy;
TURE door in the heater distributor assembly. All
incoming &quot;outside&quot; air is directed around the heater core
in the COLD position on through the core in the HOT
position. The desired outlet temperature is obtained by
blending heated and unheated air according to the
setting of the temperature lever.
the system. Moving the lever to the right (toward
HEATER) opens the air door with the AIR door being
fully open at the HEATER position. Incoming air is
directed to the heater outlets (with slight air bleed to the
defroster outlets). Moving the lever between HEATER
and DEF, directs increasing amounts of air to the
defroster outlets until all air is directed to the defroster
outlets in the DEF position.
Fan Control
Heater-Def Lever
The HEATER-DEF lever controls positioning of the AIR
and DEFROSTER doors in the heater distributor
assembly. In the OFF position, no air is allowed to enter
The blower fan lever is located on the left hand side of
the control assembly. When the lever is fully down, the
blower motor is inoperative. Moving the lever upward
actuates the three speed blower motor (LOW-MED-HI).
C O M P O N E N T PART REPLACEMENT
BLOWER MOTOR
Removal (Fig. 4)
1. Disconnect battery ground cable.
G Models - Remove the battery.
2. Disconnect the blower motor lead wire.
3. Remove the five blower motor mounting screws and
remove the motor and wheel assembly. Pry gently
on the blower flange if the sealer acts as an
adhesive.
4. Remove the blower wheel to motor shaft nut and
separate the wheel and motor assemblies.
5. To install a new motor, reverse Steps l-4 above.
NOTE: The following precautions should be
taken to assure proper installation:
a. Assemble the blower wheel to the motor with
the open end of the wheel away from the blower
motor.
b. If the motor mounting flange sealer has
hardened, or is not intact, remove the old sealer
and apply a new bead of sealer to the entire
circumference of the mounting flange.
c. Check blower operation; blower wheel should
rotate freely with no interference.
HEATER DISTRIBUTOR AND CORE
ASSEMBLY
C-K Models
Replacement (Fig. 5)
Fig. 4-Blower Motor Assembly
1. Disconnect the battery ground cable.
2. Disconnect the heater hoses at the core tubes and
drain engine coolant into a clean pan. Plug the core
tubes to prevent coolant spillage at removal.
3. Remove the nuts from the distributor duct studs
projecting into the engine compartment.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
4. Remove the glove box and door assembly.
5. Disconnect the Air-Defrost and Temperature door
cables.
6. Remove the floor outlet and remove the defroster
duct to heater distributor duct screw.
7. Remove the heater distributor to dash panel screws.
Pull the assembly rearward to gain access to wiring
harness and disconnect all harness attached to the
unit.
8. Remove the heater-distributor from the vehicle.
9. Remove the core retaining straps and remove the
core.
10. To install, reverse Steps 1-9 above.
NOTE: Be sure core to case and case to dash
panel sealer is intact before assembling unit.
G Models
Replacement (Fig. 6)
1. Disconnect the battery ground cable.
2. Place a clean pan under the vehicle and then
disconnect the heater core inlet and outlet hoses at
the core connections (see &quot;H eater Hoses-Replacem ent&quot; later in this section). Quickly plug the heater
hoses and support them in a raised position. Allow
the coolant in the heater core to drain into the pan
on the floor.
3. Disconnect the right hand air distributor hose from
the heater case and rotate it up out of the way.
4. Pry off the temperature door cable eyelet clip and
then remove the bowden cable attaching screw.
5. Remove the distributor duct to heater case screws
and pull the duct rearward out of the heater case
retainer.
6. Remove the four heater case to dash screws and
1A-5
then remove the heater case and core as an
assembly. Tilt the case assembly rearward at the top
while lifting up until the core tubes clear the dash
openings.
7. Remove the core retaining strap screws and remove
the core.
8. To install a new core, reverse Steps 1-7 above.
NOTE: Be sure core to case and case to dash
panel sealer is intact before assembling unit.
HEATER HOSES
Heater hoses are routed from the water pump and
thermostat housing (radiator on automatic transmission
vehicles) to the core inlet and outlet pipes as shown in
Figure 7. Hoses are attached at each end with screw type
clamps.
Replacement
The heater core can be easily damaged in the area of the
core tube attachment seams whenever undue force is
exerted on them. Whenever the heater core hoses do not
readily come off the tubes, the hoses should be cut just
forward of the core tubes. The portion of the hose
remaining on the core tube should then be split
longitudinally. Once the hoses have been split, they can
be removed from the tubes without damage to the core.
CENTER DISTRIBUTOR DUCT - G Models
Replacement (Fig. 8)
1. Disconnect the battery ground cable.
2. Unsnap the engine cover front latches. Remove the
two cover to floorpan screws and remove the cover.
3. Remove the heater core case and core as an
LIGHT DUTY TRUCK SERVICE MANUAL
1A-6 HEATER A N D AIR C O N D IT IO N IN G
Fig. 7 -Heater Hose Routings
4.
5.
6.
7.
assembly (see &quot;Heater Distributor and CoreReplacement&quot;).
Disconnect the right hand heater outlet hose and
the two defroster hoses from the distributor duct.
Disconnect the air and defroster door cables by
prying off the eyelet clips and removing the cable
attaching screws.
Pull the center distributor duct to the right and
remove it from the vehicle.
To install, reverse Steps 1-6 above.
NOTE: Check cable and door operation;
cables should be free from kinks or binding
and doors should close properly. If cable
adjustment is necessary, see &quot;Bowden CableAdjustment.&quot;
LEFT DISTRIBUTOR DUCT - G Models
Replacement (Fig. 8)
1. Disconnect the battery ground cable.
2. Unsnap the engine cover front latches. Remove the
two cover to floorpan screws and remove the cover.
3. Remove the duct bracket screw and remove the
duct.
4. To install, reverse Steps 1-3.
NOTE: All three bowden cables are routed
under the duct. It may be necessary to hold
the cables down as the duct is being installed.
Be sure the left duct is fully installed over the
center duct.
DEFROSTER DUCT
The defroster hose and outlet assemblies are illustrated
in Figure 9.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-7
LEFT
DISTRIBUTOR
DUCT
CENTER
DISTRIBUTOR
DUCT
HEATER
CORE
CASE
Fig. 8-Distributor Ducts-G Models
CONTROL ASSEMBLY
C-K Models
Replacement (Fig. 10)
1. Disconnect the battery ground cable.
2. Remove the radio as outlined in Setction 15 of this
manual.
3. Remove the instrument panel bezel.
4. Remove the control to instrument panel screws and
lower the control far enough to gain access to the
bowden cable attachments.
CAUTION: Be careful not to kink the bowden
cables.
5. Disconnect the bowden cables and the blower
switch wiring harness.
6. Remove the control through the radio opening.
7. If a new unit is being installed, transfer the blower
switch to the new unit.
8. To reinstall, reverse Steps 1-6 above.
G Models
Replacement (Fig. 11)
1. Disconnect the battery ground cable.
2. Remove the ignition switch from the instrument
panel (see Section 12 of this manual).
3. Remove the control to instrument panel mounting
screws and carefully lower the control far enough to
gain access to the bowden cable attachments.
CAUTION: Care should be taken to prevent
kinking the bowden cables while lowering the
control.
4. Disconnect the three bowden cables, the control
illumination bulb, the blower switch connector and
remove the control from the vehicle.
5. Remove the blower switch screws and remove the
blower switch.
6. To install, reverse Steps 1-5 above.
CONTROL CABLES
C-K Models
Replacement
1.
2.
3.
4.
Disconnect the battery ground cable.
Remove the instrument panel bezel.
Remove the control to instrument panel screws.
Raise or lower control as necessary to remove cable
push nuts and tab attaching screws.
5. Remove glove box and door as an assembly.
6. Remove cable push nut and tab attaching screw at
door end of cable.
LIGHT DUTY TRUCK SERVICE MANUAL
1 A-8 HEATER A N D AIR C O N D IT IO N IN G
C-K MODELS
DEFROSTER HOSES
G MODELS
Fig. 9 - D e f r o s t e r O u tle ts
7. Remove cable from retaining clip and remove cable
assembly.
8. To install, reverse Steps l-7 above.
CAUTION: Be careful not to kink the cable
during installation. Be sure to route the cable
as when removed.
G Models
Replacement (Fig. 12)
1. Disconnect the battery ground cable.
2. Unsnap the engine cover front latches. Remove the
two cover to floorpan screws and remove the cover.
3. Remove the left distributor duct attaching screw
and remove the duct.
4. Defroster Cable Only - Remove the radio speaker
bracket to dash panel (2) screws.
5. Pry off the cable eyelet clip at both the door and
control lever. Remove the cable attaching screw at
both door and control locations.
6. Attach a 4’ piece of wire to the door end of the
cable. Place protective tape around the cable
mounting tab and attached wire and carefully pull
the cable from the vehicle. Remove the tape and
disconnect the 4’ piece of wire.
NOTE: On defroster cables, pull rearward
slightly on the radio speaker bracket to get
clearance for cable removal.
7. To install, attach the new cable to the 4’ piece of
wire. Tape the mounting tab and attached wire.
Carefully pull the new cable into position.
8. Reverse Steps 1-5.
NOTE: If cable adjustment is required, see
below.
Adjustment
1. Disconnect the battery ground cable.
2. G Model Air and Defroster Door Cables-Unsnap the
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
1A-9
DEFROSTER
CABLE
JER CABLE
AIR CABLE
W ITHOUT RADIO
WITH RADIO
VIEW A
Fig. 1 2 -Control Cable Routing-G Models
3.
4.
5.
6.
engine cover front latches. Remove the two cover to
floorpan screws and remove the engine cover.
C-K Models-Remove glove box and door as an
assembly.
Pry off the appropriate cable eyelet clip and
disconnect the cable from the door.
Remove the cable retaining screw.
While holding the cable with pliers, rotate the
mounting tab on the cable to lengthen or shorten
the cable, whichever is required.
NOTE: Do not pinch the cable too tightly or
damage to the cable could result.
Install the cable, reversing Steps 1-4 above.
BLOWER SWITCH
C-K Models
Replacement (Fig. 10)
1. Disconnect the battery ground cable.
2. Remove the instrument panel bezel.
3. Remove the control to instrument panel screws and
lower the control onto the radio.
4. Disconnect the switch electrical harness.
5. Remove the switch attaching screws and remove the
switch.
6. To install, reverse Steps 1-5 above.
G Models
Replacement (Fig. 11)
1. Disconnect the battery ground cable.
2. Disconnect the blower switch wiring harness
connector at the switch.
3. Remove the two switch attaching screws and
remove the switch assembly.
4. To install a new switch, reverse Steps 1-3 above.
RESISTOR
Replacement (Figs. 4 and 6)
1. Disconnect the wiring harness at the resistor
connector.
2. Remove the two resistor mounting screws and
remove the resistor.
3. To install a new resistor, reverse Steps 1 and 2
above.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-10 HEATER A N D AIR C O N D IT IO N IN G
DIAGNOSIS
C AUSE AND C O R R E C T I O N
TROUBLE
Temperature o f heater a i r a t o u tle ts
senger compartment.
too
Temperature o f heater a i r a t o u tle ts
w i l l n o t b u i l d up s u f f i c i e n t h e a t .
adequate but
Inadequate d e fr o s tin g
Inadequate c i r c u l a t i o n
Erratic
or
h e a t up p a s &shy;
the
action.
of
heated a i r
heater o p e ra tio n .
Hard o p e r a t i n g
low to
through
ve h ic le .
1.
See &quot; I n s u f f i c i e n t
Check f o r
vehicle
1.
Floor
2.
Leaking
Heat
body le a ks
side
kick
Diagnostic
such a s :
pad v e n t i l a t o r s
grommets
Chart&quot;.
partially
open.
in dash.
3.
Lea kin g welded
4.
Leaks
s e a ms a l o n g
5.
Leaking
6.
L ea ks bet ween s e a l i n g edge o f
and d a s h , and b e t we e n s e a l i n g
a ss e m b l y and d a s h .
1.
Check t h a t D E FR O ST l e v e r c o m p l e t e l y opens d e f r o s t e r d o o r
in DEF p o s itio n - A d ju s t i f necessary.
2.
Insure
3.
Look f o r o b s tru ctions
obstructions.
4.
Check f o r a i r l e a k i n d u c t i n g b e t we e n d e f r o s t e r o u t l e t on
h e a t e r a s s e m b l y and d e f r o s t e r d u c t u n d e r i n s t r u m e n t panel Seal a r e a as n e c e s s a r y .
5.
Check p o s i t i o n o f
Adjust.
6.
Check p o s i t i o n o f d e f r o s t e r n o z z l e op e ni n gs
ment panel o p e n i n g s .
Mounting tabs provide
i f properly in stalle d .
1.
Check h e a t e r a i r o u t l e t
2.
I n spec t f l o o r c a r p e t to i n su re t h a t c a r p e t l i e s f l a t under
f r o n t s e a t and does n o t o b s t r u c t a i r f l o w u n d e r s e a t , and
a l s o i n s p e c t around o u t l e t du ct s to i n s u r e t h a t c a r p e t is
well fastened to f l o o r to prevent cupping o f a i r flow - Correc t
as n e c e s s a r y .
1.
Check c o o l a n t
2.
Check f o r
3.
Check o p e r a t i o n
necessary.
4.
S e d i m e n t i n h e a t e r l i n e s and r a d i a t o r c a u s i n g e n g i n e t h e r m o &shy;
s t a t t o s t i c k open - f l u s h s ys t e m and c l e a n o r r e p l a c e t h e r m o &shy;
s t a t as n e c e s s a r y .
5.
Partially
1.
Ch eck f o r l o o s e bowden c a b l e t a b
ca b le s - C o r r e c t as r e q u i r e d .
2.
Check f o r s t i c k i n g h e a t e r
using a s ilic o n e spray.
through access
rubber molding
that
ro cker
holes
and
b l o w e r and a i r i n l e t a ss e m b l y
edge o f h e a t e r d i s t r i b u t o r
kinked
plugged
for
Fill
heater
of all
doo rs open f u l l y
in d e f r o s te r ducts
bottom o f
-
and w i n d s h i e l d .
ar o u n d d o o r and w i nd o ws .
t e m p e r a t u r e and a i r
level
panel
s cr ew h o l e s .
nozzle
to
correct
to
hoses
proper
-
heater core
-
Adjust.
Remove a n y
heater
locating
relative
positive
installation
-
tab
-
to i n s t r u &shy;
position
Reinstall.
level.
relieve
bowden c a b l e s
-
-
kinks or
and doo rs
backflush
re place
hoses.
- A d j u s t as
c o r e as
necessary.
broken c o n t r o l s .
scr ews
system d o o r ( s )
or mis-adjusted
-
Lubricate
bowden
as r e q u i r e d
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-11
INSUFFICIENT HEAT DIAGNOSIS
P o sitio n th e c o n tro ls so th a t the:
T e m p eratu re lever is o n fu ll heat.
S elector o r heater lever is on Heater.
Fan sw itch is o n Hi.
•CHECK DUMP DOOR OUTLET FOR A IR FLOW
NO AIR FLOW
CHECK DEFROSTER OUTLETS FOR AIR FLOW
A d ju s t d u m p d o o r fo r no air flo w .
( I f in d o u b t as to High o r L o w a ir flo w
set selector on DEF w h ich is High and
com pare. Reset selector on Heater)
| NO OR LOW AIR FLOW |
| HIGH AIR FLOW
CHECK HEATER OUTLET A IR FLOW
|
A d ju s t d e fro ste r d o o r fo r lo w a ir flo w .
( If in d o u b t, sw itch fan
sw itch fro m Hi to Lo)
CHANGE IN AIR FLOW
Z .
I
LITTLE OR NO CHANGE IN A IR FLOW
...—
NORMAL AIR FLOW
|
LOW OR NO A IR FLOW
Check heater o u tle t te m pe ra ture
w ith 2 20 F range the rm o m e te r.
* *C h e c k s h u to ff d o o r p o s itio n fo r fu ll
system a ir flo w . A d ju s t if necessary.
(a p p ro x im a te o u tle t a ir tem peratures)
O u tle t A ir
A m b ie n t A ir
145
0
150
25
155
40
165
75
LOW A IR FLOW
NO A IR FLOW
Check heater o u tle t fo r o b s tru c tio n - re &shy;
move.
CHECK FUSE
NORMAL TEMPERATURE
Remove a ll o b s tru c tio n s u nd er fr o n t seat.
Check m o to r voltage at closest m o to r lin e
co n n e c tio n w ith a vo ltm e te r.
Car does n o t b u ild up heat - o perate ve nt
c o n tro ls and see th a t th e a ir ve nt d oors
close c o m p le te ly , if n o t, a djust.
I
FUSE B LO W N - replace fuse.
A IR F L O W -s y s te m okay.
LOW TEMPERATURE
IE
(Check th e system te m p e ra tu re a fte r re &shy;
p airin g th e item checked to c o m p le te th e
diagnosis.)
Check c o o la n t level; if
or feel all ra d ia to r and
co n n e ctio n s fo r leaks.
Check th e ra d ia to r cap
place if re q uired .
lo w , f ill. L o o k fo r
heater hoses and
Repair o r replace.
fo r damage and re&shy;
UNDER 10 VOLTS
Check b a tte ry v o lts - u nd er 10 vo lts,
recharge th e n recheck m o to r voltage.
Check w irin g and c o n n e ctio n s fo r
u nd er 10 v o lts fro m m o to r to fan
s w itch . Repair o r replace last p o in t
o f u nd er 10 v o lt reading.
Check heater a nd ra d ia to r hoses fo r k in k s
stra ig hte n and replace as necessary.
Check te m p e ra tu re d o o r fo r m ax heat po&shy;
sitio n . A d ju s t if necessary.
BLOWS FUSE
OVER 10 VOLTS
Remove p o sitive lead fro m m o to r and
replace fuse.
FUSE R E M A IN S O K - rem ove m o to r
and check fo r o b s tru c tio n in system
opening, if none, R E P LA C E M O T O R .
If o b s tru c tio n , rem ove m aterial and
re -in s ta ll m o to r.
BLO W S FUSE - check fo r shorted
w ire in b lo w e r e lectric c ir c u it See Heater C irc u it D ia g no stic C h art.
A p p ly exte rn a l g ro un d, (ju m p e r w ire) to
m o to r case. IN C R E A S E D A l R FLO W re p air g round.
| HEATER CORE |
FUSE OK
| Feel tem peratures o f heater in le t and o u tle t hoses. [
WARM INLE T AND OUTLET HOSES
S AM E A l R FLO W - rem ove m o to r and
check f o r o b s tru c tio n in system o p e n &shy;
ing. I f none, R E P LA C E M O T O R . If
o b s tru c tio n , rem ove m aterial and re &shy;
install m o to r.
|
FUSE O K - See Heater C irc u it
D iagnostic C h art.
Check engine th e rm o s ta t.
| HOT IN LET AND WARM O UTLET HOSES |
Check p u lleys, b e lt te n sio n , etc., f o r p ro &shy;
per o p e ra tio n . Replace o r service as neces&shy;
sary.
I
............
'CH ECK FOR C-K MODELS
ONLY
■CHECK FOR G MODELS
ONLY
Remove hoses fro m heater core. Reverse
flu sh w ith tap w a ter. I f plugged, re p air or
replace.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-12
HEATER
HEATER C I R C U I T D I A G N O S I S *
BLOW ER M OTO R IN O P E R A T IV E
(A N Y SPEED)
AND
Check fuse
in fuse panel.
AIR
X
FUSE BLOW N
FUSE OK
I
C O N D IT IO N IN G
' 1
The fo llo w in g tests should be made w ith
W ith Ig n itio n sw itch in
&quot; R U N &quot; p o s itio n and blow er
the ig n itio n switch in &quot; R U N &quot; po s itio n
speed sw itch &quot; O N &quot; use
the blow er speed sw itch &quot; O N &quot; and the
lever on heat position.
meter to locate sh o rt in one
I
o f the fo llo w in g w ires:
1. From fuse panel to blow er
Check blower m o to r ground
speed sw itch .
1
2. From b lo w e r speed sw itch
to heater resistor.
POOR OR NO G RO UND
G R O U N D OK
Repair ground
Check m o to r conn ector
~'I
3. From heater resistor to
blow er.
T
w ith 12 v o lt test lig h t.
N ote: S h o rt c ir c u it m ay be
in te rm itte n t. If m eter does
n o t in dicate a s hort c irc u it,
move harness around as
LA M P LIG H TS
I
m uch as possible to re-create
short c irc u it. W atch and
Replace M otor
listen fo r arcing.
L A M P DOES NO T L IG H T
Use 12 v o lt test lig h t and check feed
te rm in a l (b ro w n ) on blow er speed switch.
L A M P DOES NO T L IG H T
I
Check blower feed wire in connector
on resistor with 12 volt test light.
L A M P L IG H T S
Repair open in feed wire
from resistor to blower motor.
LIGHT
L A M P L IG H T S
Repair open in b ro w n w ire
Replace sw itch
DUTY
L A M P DOES NO T L IG H T
TRUCK
fro m b low er speed sw itch
to fuse panel.
SERVICE
MANUAL
Fig. 1 3 -Heater Circuit Diagnosis
* See heater c irc u it diagrams
HEATER A N D AIR C O N D IT IO N IN G
1A-13
Fig. 14-Heater Wiring Diagrams
LIGHT DUTY TRUCK SERVICE MANUAL
1A-14 HEATER A ND AIR C O N D IT IO N IN G
AUXILIARY HEATER
INDEX
General D escription......................................................................
C ontrols...........................................................................................
Component Replacement and Repairs....................................
Diagnosis...........................................................................................
1A-14
1A-14
1A-16
1A-17
GENERAL DESCRIPTION
An auxiliary heater is available as a dealer installed
accessory to provide additional heating capacity for the
rearmost extremities of the C-K (06) and G models.
This unit operates entirely independent of the standard
heater and is regulated through its own controls at the
instrument panel.
This system consists of a separate core and fan unit
mounted as shown in Figures 15 and 16.
Heater hoses extend from the unit to the front of the
vehicle where they are connected to the standard heater
hoses with &quot;tees&quot;. An &quot;on-off&quot; water valve is installed in
the heater core inlet line in the engine compartment.
This valve must be operated manually—&quot;on&quot; for cold
weather, &quot;off&quot; in warm weather. The purpose of the
valve is to cut off coolant flow to the auxiliary core
during warm weather and eliminate the radiant heat that
would result.
CONTROLS
Two methods of control are employed with this system:
Water Valve (Fig. 17)
When heat is desired, the water valve must be in the
&quot;on&quot; position (valve located in the engine compartment
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-15
AUXILIARY HEATER
(110&quot; W.B. WITH REAR SEATS)
EXISTING HEATER
CONTROL SWITCH
AUXILIARY HEATER
(110&quot; W.B. WITHOUT REAR SEATS)
(ALL 125&quot; W.B. MODELS)
WATER VALVE
Fig. 1 6 -A u x ilia ry H e a te r In s ta lla tio n s (G M o d e ls )
IN S T A L L V A L V E W IT H A R R O W
P O IN T IN G A W A Y F R O M TEE.
O R IE N T V A L V E S O '■ O N '&quot; 'O F F ”
IS VISIB LE
Fig. 1 7 - W a t e r Valve In s ta lla tio n
- G M o d e l S how n as
Fig. 1 8 -A u x ilia r y H e a te r C o n tro l
T y p ic a l
in the core inlet line). During the summer months, this
valve should be placed in the &quot;off&quot; position.
the instrument panel, to the right of the steering column.
Fully up, the blower is inoperative; fully down the
blower is on HI.
Fan Switch (Fig. 18)
The three speed fan switch (LOW-MED-HI) is located in
LIGHT DUTY TRUCK SERVICE MANUAL
1A-16 HEATER A N D AIR C O N D IT IO N IN G
Fig. 19--Control and Resistor Mountings
C O M P O N E N T REPLACEMENT A N D REPAIRS
Since a detailed list of installation instructions is
included with the auxiliary heater unit, replacement
procedures will not be repeated in this section.
CAUTION: G Models-- When replacing heater
hoses, maintain a 1-1/4&quot; minimum clearance
between the auxiliary heater core lines and the
exhaust pipe. Observe minimum clearances as
shown in Figure 20.
All Models-Draw hoses tight to prevent sag or
rub against other components. Be sure to route
hoses through all clamps as originally installed.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-17
D IA G N O S IS
inoperative on C-K models (equipped with
Overhead Air Conditioning), check that the
connectors have not been interchanged with
one another.
Refer to the &quot;Standard Heater&quot; section of this manual
for diagnostic information; see Electrical Diagram
Figure 21.
NOTE: If the heater blower motor is
MED
3
BLOWER
M
RESISTOR
— | 5 l1
| 552k
2 k — 140RG--------[ 52] [ 52I - I 4 BLK —
1791
72
I-----------uI40RGn p n ---------------------
-14 LT BLU■14 YEL-
■14 BLK— [5 2 ] [5 2 ]— 14 BLK--------
D
0
FUSE
PANa
IGN
UNFUSED ________
12 BRN—- | 15AMP
J-12 BRN'
INLINE FUSE
50
140RG
BLOWER
MOTOR
&gt;— 14 LT BLU'
14 YEL■12BRN-
50 52
F
L 14 BLK
BLOWER SWITCH
Fig. 21—Electrical Diagram - All Models
LIGHT DUTY TRUCK SERVICE MANUAL
1A-18 HEATER A ND AIR C O N D IT IO N IN G
AIR CONDITIONING
INDEX
General Description.........................................................1A-19
Four-Season System (C-K M odels)......................... .1A-19
Floor Mounted System (G Models)........................ .1A-19
Overhead Systems (C-K-G Models)........................ .1A-19
Motor Home Chassis System..................................... .1A-19
Theory of Operation........................................................1A-20
H eat.................................................................................... .1A-20
Refrigerants.......................................................................1A-23
Air Conditioning.............................................................1A-26
Basic Air Conditioner....................................................1A-26
Main Units of the System......................................... .1A-28
Chemical Ingredients of an Air Conditioning
System...............................................................................1A-35
Primary Causes of System Failures........................ .1A-36
System Controls.............................................................. .1A-38
General Inform ation........................................................1A-39
Precautions in Handling R efrigerant-12.................1A-39
Precautions in Handling Refrigerant Lines...........1A-40
M aintaining Chemical Stability in the
Refrigeration System ............................................... .1A-40
J-8393 Charging Station................................................1A-41
Gauge S et..........................................................................1A-41
Vacuum Pump................................................................. .1A-42
Leak Testing the System ............................................ .1A-42
Availability of Refrigerant-12....................................1A-43
Compressor O il............................................................... .1A-44
Compressor Serial N um ber........................................ .1A-44
Inspection and Periodic Service...................................1A-44
Pre-Delivery Inspection..................................................1A-44
6000 Mile Inspection......................................................1A-44
Periodic Service.............................................................. .1A-44
Evacuating and Charging Procedures....................... .1A-44
Air Conditioning System C apacity......................... .1A-44
Installing Charging Station........................................ .1A-44
Purging the System........................................................1A-45
Evacuating and Charging the System.....................1A-45
Performance Test........................................................... .1A-47
Performance D ata.......................................................... .1A-48
Checking O il.....................................................................1A-49
Refrigerant Quick-Check Procedure....................... ..1A-50
Maintenance and Adjustm ents.....................................1A-51
Thermostatic Switch.......................................................1A-51
Expansion Valve............................................................. .1A-52
Engine Idle Com pensator.............................................1A-53
General Repair Procedures.......................................... .1A-53
Preparing System for Replacement of Component
Parts.................................................................................. .1A-53
Foreign Material in the System ................................1A-53
Refrigerant Line Connections....................................1A-53
Repair of Refrigerant Leaks..................................... .1A-54
Refrigerant Hose Failure..............................................1A-54
Com pressor........................................................................1A-55
Compressor F ailure........................................................1A-57
False Compressor Seizure........................................... .1A-57
Collision Procedure-All Vehicles................................1A-57
Component Part Replacement—Four-Season
System..............................................................................
Condenser..........................................................................
Accumulator......................................................................
Blower Assembly............................................................
Evaporator Core..............................................................
Expansion Tube...............................................................
Selector Duct and Heater C o re................................
Kick Panel Air Valve...................................................
Plenum Air Valve..........................................................
Control Assembly...........................................................
Master Switch and/or Blower Switch.....................
Vacuum Tank...................................................................
Blower Resistor U nit.....................................................
Blower Motor Relay......................................................
Thermostatic Switch......................................................
Discharge Pressure Switch...........................................
Fuse.....................................................................................
Component Part Replacement - Overhead System
(C-K Models).................................................................
Rear D uct.........................................................................
Blower Motor Resistor..................................................
Blower Motor Assembly...............................................
Expansion Valve..............................................................
Evaporator Core..............................................................
Blower Motor Switch....................................................
Fuse.....................................................................................
Component Part Replacement - Floor Mounted
System (G Models)......................................................
Condenser..........................................................................
Receiver-Dehydrator......................................................
Sight Glass Replacem ent.............................................
Blower-Evaporator Cover.............................................
Blower-Evaporator Assembly......................................
Expansion Valve and/or Evaporator C o re...........
Blower M otor...................................................................
Electrical Components...................................................
Low Refrigerant Charge Protection System........
Super Heat Switch.......................................................
Thermal Fuse.................................................................
Circuit Breaker................................................................
Component Part Replacement - Overhead System
(G M odels).....................................................................
Blower-Evaporator Shroud...........................................
Blower Motor Assemblies............................................
Expansion Valves............................................................
Evaporator Core..............................................................
Resistor...............................................................................
Blower Switch...................................................................
Rear Blower R elay........................................................
Tie R elay..........................................................................
Component Part Replacement - Motor Home
Chassis U nits.................................................................
Condenser..........................................................................
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LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
Receiver-Dehydrator.......................................................1A-76
Sight G lass........................................................................1A-76
Blower-Evaporator Assembly...................................... .1A-76
Blower Assembly............................................................ .1A-77
Expansion Valve, Evaporator Case or Core..........1A-77
Thermostatic and/or Blower Switches.................... .1A-78
Resistor...............................................................................1A-78
1A-19
F use.....................................................................................1A-78
Diagnosis..............................................................................1A-78
Refrigerant System.........................................................1A-78
Compressor Diagnosis....................................................1A-80
Insufficient Cooling........................................................ 1A-81
Electrical System Diagnosis........................................ .1A-83
Vacuum System Diagnosis.......................................... .1A-87
Special Tools.......................................................................1A-94
GENERAL DESCRIPTION
FOUR-SEASON SYSTEM (C-K MODELS)
Both the heating and cooling functions are performed by
this system. Air enterning the vehicle must pass through
the cooling unit (evaporator) and through (or around)
the heating unit, in that order, and the system is thus
referred to as a &quot;reheat&quot; system.
The evaporator provides maximum cooling of the air
passing through the core when the air conditioning
system is calling for cooling. A thermostatic switch,
located in the blower-evaporator case, acts to control
compressor operation by sensing the fin temperature of
the evaporator core.
System operation is as follows: Air, either outside air or
recirculated air, enters the system and is forced through
the system by the blower. As the air passes through the
evaporator core, it receives maximum cooling if the air
conditioning controls are calling for cooling. After
leaving the evaporator, the air enters the Heater and Air
Conditioner Selector Duct Assembly where, by means of
diverter doors, it is caused to pass through or to bypass
the heater core in the proportions necessary to provide
the desired outlet temperature. Conditioned air then
enters the vehicle through either the floor distributor
duct or the dash outlets. When, during cooling
operations, the air is cooled by the evaporator to below
comfort level, it is then warmed by the heater to the
desired temperature. During &quot;heating only&quot; operations,
the evaporator will not be in operation and ambient air
will be warmed to the desired level in the same manner.
The dash outlets are rectangular in design. The outlets
can be rotated horizontally or vertically to direct air as
desired. Under the left distributor duct is located a floor
cooler which can be rotated to provide cooling air or shut
off completely.
cooling) and then directed into the vehicle through
adjustable outlets located in the ducts.
A thermostatic switch, located on the evaporator cover, is
used to control compressor operation by sensing air
temperature as it leaves the evaporator core.
OVERHEAD SYSTEMS (C-K-G MODELS)
These systems (C69 on C-K Models, C63 on G Models)
operate in conjunction with the Four-Season System (CK Models) or Floor Mounted System (G M odels)-they
do not operate independently.
NOTE: Overhead system kits are available
for non-factory installation on C-K Models,
providing the vehicle is equipped with the
front system.
Like the floor-mounted system, these units are self
contained, operating on inside (recirculated) air only. Air
is drawn into the unit, passed through the evaporator
core and then directed into the passenger compartment
through adjustable outlets in the air distributor duct.
System control is through the thermostatic switch in the
front system. The only control on the overhead system is
a three speed blower switch.
MOTOR HOME CHASSIS SYSTEM
This system performs the cooling functions only. When
FLOOR MOUNTED SYSTEM (G MODELS)
This system (C62) performs the cooling functions only.
When heating (above ambient temperatures) is desired,
the standard equipment heater must be used. When air
conditioning is desired, be sure the heater is completely
shut off.
This self contained unit (fig. 22), operates on recirculated
inside air only. Recirculated air is drawn into the unit,
passes through the evaporator core (receiving maximum
Fig. 22--C62 Interior Components (G Models)
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1A-20 HEATER A N D AIR C O N D IT IO N IN G
heating (above ambient temperatures) is desired, the
vehicle heater must be used. When air conditioning is
desired, the heater should be completely shut off.
This self-contained unit is bracket mounted to the dash
by the body manufacturer. It operates on inside
(recirculated) air only. Air is drawn into the unit, passed
through the evaporator core (receiving maximum
cooling) and then directed into the vehicle through
adjustable outlets.
A thermostatic switch, located on the face plate is used to
control compressor operation by sensing air temperature
as it leaves the evaporator core.
THEORY OF OPERATION
HEAT
We all know what air conditioning does for us but very
few understand how or why it works. An air conditioner
is functionally very similar to a refrigerator. A
refrigerator is a simple mechanism which, surprisingly
enough, works quite a bit like a teakettle boiling on a
stove. That may sound far-fetched, but there is more
similarity between the two than most of us would
suspect. A modern refrigerator can make icecubes and
keep food cool and fresh only because a liquid called the
refrigerant boils inside the freezer.
Everyone knows a boiling teakettle is &quot;hot&quot; and a
refrigerator is &quot;cold&quot;. We usually think of &quot;cold&quot; as a
definite, positive condition. The only way we can define
it is in a rather negative sort of way by saying &quot;cold&quot; is
simply the lack of heat, just as darkness is the lack of
light. We can’t make things cold directly. All we can do
is remove some of the heat they contain and they will
become cold as a result. And that is the main job of any
icebox or refrigerator. Both are simply devices for
removing heat.
All substances contain some heat. Theoretically, the
lowest temperature that any substance could obtain is
459&deg; Fahrenheit below Zero. This is called &quot;absolute
zero&quot; and anything warmer than this contains heat.
Since man has never succeeded in getting all the heat out
of an object, we must think about the transfer of heat
from one object to another when talking about
controlling temperatures.
Fahrenheit) They can tell how hot a substance is, but
they can’t tell us everything about heat.
When we put a teakettle on a stove, we expect it to get
hotter and hotter until it finally boils. All during the
process, we can tell exactly how hot the water is by
means of a thermometer (fig. 24). Our thermometer will
show us that the flame is just as hot when we first put the
teakettle on the stove as it is when the water finally boils.
Why doesn’t the water boil immediately? Why does it
take longer to boil a quart of water than a cupful?
Obviously temperature isn’t the only measurement of
heat.
Even though heat is intangible, it can be measured by
quantity as well as intensity. Thermometers indicate only
the intensity of heat. The unit for measuring quantity of
heat is specified as that amount necessary to make 1
pound of water 1 degree warmer (fig. 25). We call this
quantity of heat a British Thermal Unit. Oftentimes, it is
abbreviated to B.T.U.
Perhaps we can get a better idea of these two
characteristics of heat if we think of heat as a sort of
coloring dye. If we add one drop of red dye to a glass of
water, it will turn slightly pink. Another drop will make
the water more reddish in color (fig. 26). The more drops
of dye we add, the redder the water will get. Each drop
of dye corresponds to 1 B.T.U. and the succeedingly
deeper shades of red are like increases in temperature.
Transfer of Heat
The only thing that will attract heat is a colder object.
Like water, which always flows downhill, heat always
flows down a temperature scale - from a warm level
down to a colder one. When we hold our hands out
toward the fireplace, heat flows from the hot fire out to
our cold hands (fig. 23). When we make a snowball, heat
always flows from our warm hands to the colder snow. In
an icebox, the ice always is colder than the stored food,
so heat is drawn out of the warm food by the colder ice.
Measurement of Heat
Everyone thinks he knows how heat is measured.
Thermometers are used in every home. (Whenever we
speak of temperature from
now on, we will
mean
Fig. 23-Heat Transfer
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1A-21
Fig. 25-Quantity of Heat = B.T.U.
Fig. 24--Measurement of Heat
It may seem a little puzzling to talk about heat in a book
on air conditioning...but, when you stop to think about it,
we are handling heat exclusively. Although we ordinarily
think of an air conditioner as a device for making air
cold, it does that indirectly. W hat it does is to take heat
away from the air and transfer that heat outside the
vehicle.
We know now that cold is nothing more than the
absence of heat, and that heat always flows from a warm
object to a colder one. We also have a clearer idea of
how heat is measured.
From everything we’ve learned about heat so far, it
seems to behave in a perfectly normal manner. Yet
sometimes heat will disappear without leaving a single
clue.
Ice vs Water For Cooling
Every once in a while in the old days, the iceman would
forget to stop by to refill the icebox. Ocassionally, as the
last sliver of ice melted away, somebody would come up
with a bright idea. He would remember that the water in
the drainpan always felt icecold when he emptied it
other times. So, he would get the thermometer out and
check its temperature. Sure enough, it usually was about
as cold as the ice. Why not put the drainpan back in the
ice compartment to keep things cold until the iceman
returned the next day?
For some strange reason, the icebox never stayed cold.
The drain water soon got quite warm and in a couple of
hours, the butter in the icebox would begin to melt, the
milk would start to sour, and the vegetables would wilt.
The drain water was only a few degrees warmer than the
ice yet it didn’t draw nearly as much heat out of the
stored foods. The difference between the behavior of
cold drain water and ice is the real secret as to how any
refrigerator works, and we can easily see this by using an
ordinary thermometer.
When we put a drainpan full of cold water into the ice
compartment, we expect the heat to flow from the warm
foods to the colder water. Remember, that heat always
flows from a warm object to a colder object and when we
add heat to water, it gets warmer. Each B.T.U. of heat
added to a pound of water makes it one degree warmer.
If we were to put a thermometer in the cold drain water,
we would see the temperature gradually creep upwards.
That is to be expected because heat is flowing into the
cold water making it warmer. Before long the water
would be as warm as the stored foods. Then the water
could no longer attract heat because heat will not flow
from one warm object to another equally warm object.
Since we no longer can draw heat out of the foods we no
longer are cooling them.
Now, let’s see what happens when we put ice instead of
cold water into the icebox. This time, we’ll set the
thermometer on top of the ice (fig. 27). W hen we first
look at the thermometer, it reads 32&deg;. A couple of hours
later, the ice chunk is smaller because some of the ice
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has already melted aw ay-but the thermometer still reads
32&deg;.
All this time, the ice has been soaking up heat, yet it
never gets any warmer no matter how much heat it
draws from the stored food. On the other hand, the cold
drain water got progressively warmer as it soaked up
heat. The addition of heat will make water warmer yet
won’t raise the temperature of ice above the 32&deg; mark.
If we fill one drinking glass with ice and another with
cold water, and put both glasses in the same room where
they could absorb equal amounts of heat from the room
air, we will find it takes much, much longer for the ice to
melt and reach room temperature than it did for the
water in the other glass to reach the same temperature.
Obviously, most of the heat was being used to melt the
ice. But it was the heat that apparently disappeared or
was transformed because it couldn’t be located with a
thermometer. To describe this disappearing heat,
scientists chose the word &quot;latent&quot; which means hidden.
Latent Heat
So latent heat is nothing more nor less than hidden heat
which can’t be found with a thermometer.
At first it was thought that latent heat was in the water
that melted from the ice. But that wasn’t exactly the right
answer because, upon checking water temperature as it
melts from ice, it will be found that it is only a shade
warmer than the ice itself. It is not nearly warm enough
to account for all the heat the ice had absorbed. The only
possible answer is that the latent heat had been used up
to change the ice from a solid into a liquid.
Many substances can be either a solid, or a liquid, or a
gas. It just depends on the temperature whether water for
example was a liquid, or a solid (ice), or gas (steam) (fig.
28).
All solids soak up huge amounts of heat without getting
any warmer when they change into liquids, and the same
thing will happen when a substance changes from a
liquid into a gas.
Fig. 2 7 -M e ltin g Ice Remains at 32&quot;
Fig. 2 8 -T e m p e ra tu r e D e te r m in e s T h e S ta te O f W a te r
Put some water in a teakettle, set it over a fire and watch
the thermometer as the water gets hotter and hotter, the
mercury will keep rising until the water starts to boil.
Then the mercury seems to stick at the 212&deg; mark. Put
more wood on the fire, despite all the increased heat, the
mercury will not budge above the 212&deg; mark (fig. 29).
No matter how large or hot you make the flame, you
can’t make water any hotter than 212&deg; at sea level. As a
liquid changes into a gas, it absorbs abnormally great
amounts of heat without getting any hotter.
Now we have two different kinds of latent heat, which
are quite a bit alike. To keep their identities separate,
the first one is called latent heat of fusion, which means
the same as melting. The other kind is called latent heat
of vaporization because that means the same as
evaporation.
Refrigeration
It may seem as though we have discussed heat instead of
Fig. 29--Boiling Water Never Exceeds 212&deg; at Sea
l_evel
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refrigeration. But in doing so, we have learned how a
simple icebox works. It’s because the latent heat of
fusion gives ice the ability to soak up quantities of heat
without getting any warmer. Since it stays cold, it can
continue to draw heat away from stored foods and make
them cooler.
The latent heat of vaporization can be even better
because it will soak up even more heat.
Whenever we think of anything boiling, we think of it
being pretty hot, but that’s not true in every case. Just
because water boils at 212&deg; doesn’t mean that all other
substances will boil at the same temperature. Some
would have to be put into a blast furnace to make them
bubble and give off vapor. On the other hand, others will
boil violently while sitting on a cake of ice.
And so each substance has its own particular boiling
point temperature. But regardless of whether it is high or
low, they all absorb unusually large quantities of heat
without getting any warmer when they change from a
liquid into a vapor.
Consequently, any liquid that will boil at a temperature
below the freezing point of water, will make ice cubes
and keep vegetables cool in a mechanical refrigerator.
REFRIGERANTS
The substance that carries heat out of a refrigerator
cabinet is the refrigerant.
There are many refrigerants known to man. In fact, any
liquid that can boil at temperatures somewhere near the
freezing point of water can be used.
But a boiling point below the temperature at which ice
forms is not the only thing that makes a good
refrigerant. A refrigerant should also be non-poisonous
and non-explosive to be safe. Besides that, we want a
refrigerant that is non-corrosive and one that will mix
with oil.
Chemists tried to improve existing natural refrigerants.
But after exploring along that line, they still hadn’t
succeeded. They started from scratch and juggled
molecules around to make an entirely new refrigerant.
Eventually they succeeded by remodeling the molecules
in carbon tetrachloride. This is the same fluid that is
used in fire extinguishers and dry-cleaners’ solvents.
From this fluid, the chemists removed two chlorine
atoms and replaced them with two flourine atoms. This
newly formed fluid carried the technical chemical name
of dichlorodifluoromethane. Today, it is sold commer&shy;
cially by manufacturers as R efrigerant-12 or R-12.
Flourine is a temperamental substance, under most
conditions, it is toxic and highly corrosive. After it is
manufactured, it has to be stored in special containers
because it will eat through glass and will dissolve most
metals in short order.
Despite its rambunctious character though, fluorine is
completely tamed when it is combined with the other
substances that go to make up the refrigerant. Each is
1A-23
non-toxic, non-inflammable, non-explosive, and nonpoisonous, however, breathing large quantities of R-12
should be avoided.
Refrigerant-12
Refrigerant-12, which we use in Air Conditioning
Systems, boils at 21.7&deg; below zero. Picture a flask of R-12
sitting on the North Pole boiling away just like a
teakettle on a stove. No one would dare pick up the flask
with his bare hands because, even though boiling, it
would be so cold and it would be drawing heat away
from nearby objects so fast that human flesh would
freeze in a very short time.
If we were to put a flask of R-12 inside a refrigerator
cabinet, it would boil and draw heat away from
everything surrounding it (fig. 30). So long as any
refrigerant remained in the flask, it would keep on
soaking up heat until the temperature got clear down to
21.7&deg; below zero.
Now we can begin to see the similarity between a boiling
teakettle and a refrigerator. Ordinarily we think of the
flame pushing heat into the teakettle. Yet, it is just as
logical to turn our thinking around and picture the
teakettle pulling heat out of the flame. Both the teakettle
and the flask of refrigerant do the same thing-they both
draw in heat to boil although they do so at different
temperature levels.
There also is another similarity between the icebox and
the mechanical refrigerator. In the icebox, water from
melting ice literally carried heat out of the cabinet. In
our simple refrigerator, rising vapors do the same job.
Reusing R-12
R-12, or any other refrigerant, is too expensive just to let
float away into the Atmosphere. If there was some way
to remove the heat from the vapor and change it back
into a liquid, it could be returned to the flask and used
over again (fig. 31).
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ra3S2Qp3pj|3
This is where pressure helps, with pressure, we can
compress the vapor, thereby concentrating the heat it
contains. When we concentrate heat in a vapor that way,
we increase the intensity of the heat or, we increase the
temperature, because temperature is merely a measure&shy;
ment of heat intensity (fig. 32).
Pressure in Refrigeration
Fig. 3 1- R eu sin g R e frig e ra n t
That is where we find the biggest difference between the
old icebox and the modern refrigerator. We used to put
in new ice to replace that lost by melting. Now we use
the same refrigerant over and over again.
We can change a vapor back into a liquid by chilling it,
or do the same thing with pressure. When we condense a
vapor we will find that the heat removed just exactly
equals the amount of heat that was necessary to make
the substance vaporize in the first place.
This is called the latent heat of vaporization - the heat
that apparently disappeared when a liquid boiled into a
vapor—again reappears - when that same vapor reverts
back into a liquid. It is just like putting air into a balloon
to expand it and then letting the same amount of air out
again to return the balloon to its original condition.
We know that any substance will condense at the same
temperature at which it boiled. This temperature point is
a clear-cut division like a fence. On one side, a substance
is a liquid. Immediately on the other side it is a vapor.
Whichever way a substance would go, from hot to cold
or cold to hot, it will change its character the moment it
crosses over the fence.
W ater will boil at 212&deg; under normal conditions.
Naturally, we expect steam to condense at the same
temperature. But whenever we put pressure on steam, it
doesn’t. It will condense at some temperature higher
than 212&deg;. The greater the pressure, the higher the
boiling point and the temperature at which a vapor will
condense. This is the reason why pressure cookers cook
food faster, since the pressure on the water permits it to
boil out at a higher temperature.
We know that R-12 boils at 21.7&deg; below zero. A
thermometer will show us that the rising vapors, even
though they have soaked up lots of heat, are only slightly
warmer. But the vapors must be made warmer than the
room air if we expect heat to flow out of them. The
condensing point temperature must be above that of
room air or else the vapors won’t condense.
Because we must use pressures and gauges in air
conditioning service, the following points are mentioned
so that we will all be talking about the same thing when
we speak of pressures.
All pressure, regardless of how it is produced, is
measured in pounds per square inch (psi).
Atmospheric Pressure is pressure exerted in every
direction by the weight of the atmosphere. At sea level
atmospheric pressure is 14.7 psi. At higher altitudes air
has less weight (lower psi).
Any pressure less than atmospheric (14.7) is known as a
partial vacuum or commonly called a vacuum. A perfect
vacuum or region of no pressure has never been
mechanically produced.
Gauge pressure is used in refrigeration work. Gauges are
calibrated in pounds (psi) of pressure and inches of
Mercury for vacuum. At sea level, &quot;O &quot; lbs. gauge
pressure is equivalent to 14.7 lbs. atmospheric pressure.
Pressure greater than atmospheric is measured in pounds
(psi) and pressure below atmospheric is measured in
inches of vacuum. The &quot;O &quot; on the gauge will always
correspond to the surrounding atmospheric pressure,
regardless of the elevation where the gauge is being
used.
Pressure-Temperature Relationships of R-12
A definite pressure and temperature relationship exists in
the case of liquid refrigerants and their saturated vapors.
Increasing the temperature of a substance causes it to
expand. When the substance is confined in a closed
container, the increase in tem perature will be accompa&shy;
nied by an increase in pressure, even though no
mechanical device was used. For every temperature,
there will be a corresponsing pressure within the
container of refrigerant. A table of the temperaturepressure relationship of R-12 is presented below.
Pressures are indicated in gauge pressure, either positive
pressure (above atmospheric) in pounds or negative
pressure (below atmospheric) in inches of vacuum.
Thus if a gauge is attached to a container of R-12 and
the room temperature is 70&deg;, the gauge will register
approximately 70 psi pressure; in a 100&deg; room, the
pressure would be 117 psi.
Pressure and Flow
When we use a tire pump to inflate an automobile tire,
we are creating pressure only because we are &quot;pushing&quot;
against the air already entrapped inside the tire. If a tire
has a puncture in it, you could pump all day, and still not
be able to build up any pressure. As fast as you would
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HEATER AND AIR C O N D IT IO N IN G
&deg;F
Pressure (psi)
-4 0
-3 5
-3 0
-2 5
-2 0
- 15
- 10
- 5
0
+ 5
+ 10
+ 15
+ 20
+ 25
+ 30
+ 32
+ 35
+ 40
+ 45
11 . 0 *
8 .3 *
5 .5 *
2 .3 *
0.6
2.4
4.5
6.8
9.2
11.8
14.7
17.7
21.1
24.6
28.5
30.1
32.6
37.0
41.7
&deg;F
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
140
150
Pressure (psi)
46.7
52.0
57.7
63.7
70.1
76.9
84.1
91.7
99.6
108.1
116.9
126.2
136.0
146.5
157.1
167.5
179.0
204.5
232.0
In c h e s o f V a c u u m
pump the air in, it would leak out through the puncture.
Unless you have something to push against—to block the
flow of air—you can’t create more than a mere semblance
of pressure.
The same situation holds ture in an air conditioning
system. The compressor can pump refrigerant vapor
through the system, but unless it has something to push
against, it cannot build up pressure. All the compressor
would be doing would be to circulate the vapor without
increasing its pressure.
We can’t just block the flow through the system entirely.
All we want to do is put pressure on the refrigerant
vapor so it will condense at normal temperatures. This
must be done sometime after the vapor leaves the
evaporator and before it returns again as a liquid. High
pressure in the evaporator would slow down the boiling
of the refrigerant and penalize the refrigerating effect.
1A-25
and, of course, the float rides up along with it. When the
surface level of the refrigerant liquid reaches a desired
height, the float will have risen far enough to close the
valve and stop the flow of refrigerant liquid.
We have described the float and valve action as being in
a sort of definite wide open or tight shut condition.
Actually, the liquid level falls rather slowly as the
refrigerant boils away. The float goes down gradually
and gradually opens the valve just a crack. At such a
slow rate of flow, it raises the liquid level in the
evaporator very slowly.
It is easy to see how it would be possible for a stablized
condition to exist. By that, we mean a condition wherein
the valve would be opened enough to allow just exactly
the right amount of refrigerant liquid to enter the system
to take the place of that leaving as a vapor.
Refrigerator Operation
W e’ve now covered all the scientific ground-rules that
apply to refrigeration. Try to remember these main
points. All liquids soak up lots of heat without getting
any warmer when they boil into a vapor, and, we can use
pressure to make the vapor condense back into a liquid
so it can be used over again. W ith just that amount of
scientific knowledge, here is how we can build a
refrigerator.
We can place a flask of refrigerant in an icebox. We
know it will boil at a very cold temperature and will
draw heat away from everything inside the cabinet (fig.
32).
We can pipe the rising vapors outside the cabinet and
thus provide a way for carrying the heat out. Once we
get the heat-laden vapor outside, we can compress it with
a pump. With enough pressure, we can squeeze the heat
Controlling Pressure and Flow
Pressure and flow can be controlled with a float valve, or
with a pressure-regulating valve.
The float valve type will give us a better idea of pressure
and flow control, let’s look at it first.
It consists simply of a float that rides on the surface of
the liquid refrigerant. As the refrigerant liquid boils and
passes off as a vapor, naturally the liquid level drops
lower and lower. Correspondingly, the float, because it
rides on the surface of the refrigerant, also drops lower
and lower as the liquid goes down.
By means of a simple system of mechanical linkage, the
downward movement of the float opens a valve to let
refrigerant in. The incoming liquid raises the fluid level
Fig. 32--Basic Refrigerant Circuit
LIGHT DUTY TRUCK SERVICE MANUAL
1A-26 HEATER AND AIR C O N D IT IO N IN G
out of &quot;cold&quot; vapor even in a warm room. An ordinary
radiator will help us get rid of heat.
By removing the heat, and making the refrigerant into a
liquid, it becomes the same as it was before. So, we can
run another pipe back into the cabinet and return the
refrigerant to the flask to be used over again.
That is the way most mechanical refrigerators work
today. Now, let’s look at air conditioning to see the
benefits of air conditioning and how an air conditioner
works.
AIR CONDITIONING
Because air-conditioning has always been very closely
allied with mechanical refrigeration, most of us are apt
to think of it only as a process for cooling room air.
Air Conditioning goes beyond the mere cooling of the
air. It controls the humidity, cleanliness and circulation
of the air.
Whenever it gets warm and muggy in the summertime,
someone is almost sure to say, &quot;It’s not the heat...it’s the
humidity.&quot; But that is only partly right. Actually it is a
combination of the two that makes us feel so
warm...temperature alone is not the only thing that
makes us uncomfortable.
Humidity is the moisture content of the air. To a certain
extent, it is tied in with the temperature of the air. Warm
air will hold more moisture than will cold air. When air
contains all the moisture it can hold, it is saturated, and
the relative humidity is 100%. If the air contains only
half as much water as it could hold at any given
temperature, we say that the relative humidity is 50%. If
it contains only a fifth of its maximum capacity, we say
that the relative humidity is 20%. This amount of water
vapor, or relative humidity, affects the way we perspire
on hot days.
Nature has equipped our bodies with a network of sweat
glands that carry perspiration to the skin surfaces.
Normally, this perspiration evaporates and absorbs heat
just like a refrigerant absorbs heat when it is vaporized
in a freezer. Most of the heat is drawn from our bodies,
giving us a sensation of coolness. A drop of alcohol on
the back of your hand will demonstrate this principle
convincingly. Alcohol is highly volatile, and will
evaporate very rapidly and absorb quite a bit of heat in
doing so, making the spot on your hand feel cool.
The ease and rapidity with which evaporation takes
place, whether it be alcohol or perspiration, governs our
sensation of coolness and to a certain extent,
independently of the temperature. The ease and rapidity
of the evaporation are directly affected by the relative
humidity or comparative dampness of the air. When the
air is dry, perspiration will evaporate quite readily. But
when the air contains a lot of moisture, perspiration will
evaporate more slowly; consequently less heat is carried
away from our body.
From the standpoint of comfort, air-conditioning should
control the relative humidity of the air as well as its
temperature.
By reducing the humidity, we oftentimes can be just as
&quot;cool&quot; in a higher room tem perature than otherwise
would be comfortable. Laboratory tests have shown that
the average person will feel just as cool in a temperature
of 79&deg; when the relative humidity is down around 30% as
he will in a cooler temperature of 72&deg; with a high relative
humidity of 90%.
There are practical limits though within which we must
stay when it comes to juggling humidity. For comfort, we
can’t go much below a relative humidity of 30% because
anything lower than that would cause an unpleasant and
unhealthy dryness in the throat and nasal passages.
Summertime temperatures of 85&deg; sometimes bring with
them relative humidities around 75% to 80%. To gain
maximum human comfort, an air conditioning system
should cool the air down and reduce the humidity to
comfortable limits.
Along with the cooling job it does, the evaporator unit
also removes much of the moisture from the air.
Everyone is familiar with the sight of thick frost on the
freezer of a refrigerator. That frost is simply frozen
moisture that has come out of the air.
The evaporator unit as an air conditioning system does
the same thing with this one exception. Because its
temperature is above the freezing point, the moisture
does not collect in the form of ice or frost. The moisture
remains fluid and drips off the chilling unit. A further
advantage of air conditioning is that dust and pollen
particles are trapped by the wet surfaces of the
evaporator core and then drained off along with the
condensed moisture. This provides very clean, pure air
for breathing.
BASIC AIR CONDITIONER
When we look at an air conditioning unit, we will always
find a set of coils or a finned radiator core through which
the air to be cooled passes. This is known as the
&quot;evaporator&quot;. It does the same job as the flask of
refrigerant we spoke about previously. The refrigerant
boils in the evaporator. In boiling, of course, the
refrigerant absorbs heat and changes into a vapor. By
piping this vapor outside the car we can bodily carry out
the heat that caused its creation.
Once we get vapor out of the evaporator, all we have to
do is remove the heat it contains. Since heat is the only
thing that expanded the refrigerant from a liquid to a
vapor in the first place, removal of that same heat will let
the vapor condense into a liquid again. Then we can
return the liquid refrigerant to the evaporator to be used
over again.
Actually, the vapor coming out of the evaporator is very
cold. We know the liquid refrigerant boils at
temperatures considerably below freezing and that the
vapors arising from it are only a shade warmer even
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1A-27
LIGHT DUTY TRUCK SERVICE MANUAL
1A-28 HEATER A N D AIR C O N D IT IO N IN G
though they do contain quantities of heat. Consequently,
we can’t expect to remove heat from sub-freezing vapors
by &quot;cooling&quot; them in air temperatures that usually range
between 60&deg; and 100&deg;...heat refuses to flow from a cold
object toward a warmer object.
But with a pump, we can squeeze the heat-laden vapor
into a smaller space. And, when we compress the vapor,
we also concentrate the heat it contains. In this way, we
can make the vapor hotter without adding any heat.
Then we can cool it in comparatively warm air.
That is the only responsibility of a compressor in an air
conditioning system. It is not intended to be a pump just
for circulating the refrigerant. Rather, its job is to exert
pressure for two reasons. Pressure makes the vapor hot
enough to cool off in warm air. At the same time, the
compressor raises the refrigerant’s pressure above the
condensing point at the temperature of the surrounding
air so it will condense.
As the refrigerant leaves the compressor, it is still a
vapor although it is now quite hot and ready to give up
the heat that it absorbed in the evaporator. One of the
easiest ways to help refrigerant vapor discharge its heat
is to send it through a radiator-like component known as
a condenser.
The condenser really is a very simple device having no
moving parts. It does exactly the same job as the familiar
radiator in a typical home steam-heating system. There,
the steam is nothing more than water vapor. In passing
through the radiator, the steam gives up its heat and
condenses back into water.
The purpose of the condenser, as the name implies, is to
condense the high pressure, high temperature refrigerant
vapor discharged by the compressor into a high pressure
liquid refrigerant. This occurs when the high pressure,
high tem perature refrigerant is subjected to the
considerably cooler metal surfaces of the condenser. This
is due to the fundamental laws, covered earlier, which
state that &quot;heat travels from the warmer to the cooler
surface,&quot; and that &quot;when heat is removed from vapor,
liquid is produced.&quot;
When the refrigerant condenses into a liquid, it again is
ready for boiling in the evaporator. So, we run a pipe
from the condenser back to the evaporator.
MAIN UNITS OF THE SYSTEM
These three units then; the evaporator, the compressor,
and the condenser...are the main working parts in any
typical air conditioning system. We have the evaporator
where the refrigerant boils and changes into a vapor,
absorbing heat as it does so. We have the pump or
compressor to put pressure on the refrigerant so it can
get rid of its heat. And we have a condenser outside the
car body to help discharge the heat into the surrounding
air.
Now let’s look at the compressor in detail, and some of
the components that work with these main units to
complete the air conditioning system.
Compressor
The prime purpose of the compressor (fig. 34) is to take
the low pressure refrigerant vapor produced by the
evaporator and compress it into a high pressure, high
temperature vapor which will be sent on to the
condenser.
It utilizes the principle that &quot;when a vapor is
compressed, both its pressure and temperature are
raised&quot; which we have already discussed. The compres&shy;
sor is mounted above the engine in a special rubber
mounted bracket and is belt driven from the engine
through an electromagnetic clutch pulley on the
compressor.
The compressor has three double-acting pistons, making
it a six cylinder compressor. The compressor has a 1.5
inch bore and 1.1875 inch stroke, giving it a total
displacement of 12.6 cu. in. Identification of the
compressor is by model and serial num ber stamped on a
plate on top of the compressor.
Clutch-Pulley
The movable part of the clutch drive plate is in front of
the pulley and bearing assembly. The armature plate, the
movable member, is attached to the drive hub through
driver springs and is riveted to both members. The hub
of the drive plate is pressed over a square drive key
located in the compressor shaft. A spacer and retainer
ring are assembled to the shaft and the assembly is held
in place with a self-locking nut. The pulley rim, power
element ring and pulley hub are formed into a final
assembly by molding a frictional material between the
rim and the hub with the power element ring imbedded
in the forward face of the assembly.
A two-row ball bearing is pressed into the pulley hub
and held in place by a retainer ring. The entire pulley
and bearing assembly is then pressed over the front head
of the compressor and secured by a retainer ring.
Clutch Coil
The coil is molded into the coil housing with a filled
epoxy resin and must be replaced as a complete
assembly. Three protrusions on the rear of the housing
fit into alignment holes in the compressor front head. A
retainer ring secures the coil and housing in place. The
coil has 3.85 ohms resistance at 80&deg;F. ambient
temperature and will require no more than 3.2 amperes
at 12 volts D.C. Since the clutch coil is not grounded
internally, a ground lead is required as well as a &quot;hot&quot;
lead.
Shaft Seal
The main shaft seal, located in the neck of the
compressor front head, consists of the seal assembly with
its ceramic seal face in a spring loaded cage. An &quot;O &quot;
ring seal, located within the ceramic seal, provides a seal
to the shaft surface. The contact surface of the shaft seal
seat is finished to a high polish and must be protected
against nicks, scratches and even fingerprints. Any
surface damage will cause a poor seal. An &quot;O &quot; ring,
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
1
20
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
21
2
22
3
23
4
5
24
Rear Head
Rear Head to Shell &quot; O &quot; Ring
Rear Discharge Valve Plate
Rear Suction Reed Plate
Piston Ring
Piston Drive Ball
Ball Seat
Piston
Front Suction Reed Plate
Front Discharge Valve Plate
Front Head to Shell &quot; O ” Ring
F ront Head
Coil and Housing Assembly
Coil Housing Retainer Ring
6
25
7
8
26
27
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
9
10
28
29
11
12
30
13
31
14
32
15
33
Pulley and Bearing Assembly
Pulley Bearing
Pulley Bearing Retainer Ring
Pulley and Bearing Retainer Ring
Clutch Hub and Drive Plate Assembly
Super Heat Switch, &quot; O ” Ring and
Retainer Ring (G Models Only)
High Pressure Relief Valve
Oil Pump Gears
Mainshaft Bearing (Rear)
Oil Inlet Tube &quot; 0 &quot; Ring
Oil Inlet Tube
Wobble Plate and Mainshaft Assembly
Thrust Race
16
34
35
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
1A-29
17
18
19
3 6 37
38 3 9
40
Thrust Bearing
Thrust Race
Compressor Shell
C ylinder Assembly
Shaft Seal
Shaft Seal Seat ” 0 &quot; Ring
Shaft Seal Seat
Shaft Seal Seat Retainer Ring
Absorbent Sleeve
Absorbent Sleeve Retainer
Spacer
Clutch Hub Retainer Ring
Shaft Nut
Fig. 34 -Six Cylinder Compressor- Cross Sectional View
located in an internal groove in the neck of the front
head provides a seal with the outer diam eter of the seal
seat. A retainer ring, tapered side away from the seat,
secures the seat in place. The hub and armature plate
must be removed to gain access to the seal. A shaft seal
kit contains all necessary replacement parts for field
service.
After removing the clutch drive, pulley-bearing and coil
housing assemblies, the rear head and internal
mechanism (fig. 34) may be removed from the
compressor shell. Four threaded stu4s, welded to the
compressor shell, locate the rear head and four lock nuts
secure it in place.
Rear Head
The rear head (fig. 35) has a machined cavity in the
center for the oil pump gears. This cavity, in all
compressors, is machined so that the eccentricity of the
bore is approximately .042 inch to the LEFT of the
centerline of the cavity. The counterclockwise rotation
compressor used in some other systems has the
eccentricity machined approximately .042 inch to the
RIGHT of the cavity centerline. A small diameter hole is
LIGHT DUTY TRUCK SERVICE MANUAL
1A-30 HEATER A ND AIR C O N D IT IO N IN G
drilled in the head between the two. The unit number is
stamped on a plate attached to the counterclockwise
rotation head and a decal arrow indicates the direction
of rotation.
Mainshaft
The central mainshaft, driven by the clutch-pulley when
the coil is energized, extends through the front head to
the rear head and oil pump cavity of the compressor.
The shaft revolves in needle roller bearings located in
the front and rear halves of the cylinder assembly. A
3/16&quot; internally drilled passage extends through the
shaft from the rear oil pump cavity to the shaft seal
cavity in the front compressor head. Four .078 inch
holes, drilled at 90&deg; to the main passage, direct oil under
pump pressure to the shaft seal surfaces, thrust bearings
and shaft-cylinder bearings.
Wobble Plate
The wobble plate is an angular shaped member pressed
onto the mainshaft forming the mainshaft and wobble
plate assembly (fig. 35). A woodruff key prevents
movement of the plate around the shaft. Location of the
plate on the shaft is factory set and must not be changed.
The very smooth angular faces of the plate are ground to
be parallel within .0003 inches of each other. The plate
changes the rotating action of the shaft into the
reciprocating driving force for three pistons. The driving
force is applied, through the drive balls and ball seats
(shoe discs) to the midpoint of each of the double end
pistons.
Cylinder Block
The cylinder block consists of a front and a rear half.
Three piston bores are line bored in each half during
production to assure proper alignment and parallelism.
The two halves must be serviced as an assembly to assure
correct relationship of parts.
Pistons
simple field gauging operations. Seats are marked with
their size which corresponds to the last three digits of the
piece part number.
Selection from this group must be made to provide .0005
inch to .0010 inch total clearance between the ball seats
and the wobble plate at the tightest place throughout its
360&deg; rotation (fig. 36).
Thrust Bearings
The thrust bearings, sandwiched between two thrust
races (see below) are located between the shoulders of
the wobble plate and the shoulders of both the front and
rear cylinder hubs.
Thrust Races
The steel thrust races are ground to fixed thicknesses. A
total of 14 races in increments of .0005 inch thickness
are available for field service. As in the case of the ball
seats the thrust races will be identified on the part by
their thickness, the number on the race corresponding to
the last three digits of the piece part number. The
FRONT combination of a race, bearing and race is
selected to provide the proper head clearance between
the top of the cylinder and the underside of the suction
and discharge valve plates. The REAR end combination
of bearing and races is selected to obtain .0005 inch low
limit to .0015 inch high limit running clearance between
the hub surfaces of the wobble plate and the front and
rear hubs of the cylinder (fig. 36). This allows .001 inch
tolerance between the high and low limits.
Oil Pump Gears
The oil pump gears are made of sintered iron. The inner,
or driver gear has a &quot;D &quot; shaped hole in the center which
fits over a similar area on the rear of the mainshaft.
Shell
The compressor shell has a mounting flange on the front
end and four threaded studs welded to the outside of the
rear end. The oil sump is formed into the shell and a
baffle plate is welded over the sump on the inside of the
shell.
The cast aluminum double end pistons (fig. 35), have
grooves to receive piston rings. Each ring has an oil
scraper groove which should face away from the piston
face. Two oil return passages are drilled from each ring
groove. A notch in the casting web of each piston
identifies the end of the piston which should be
positioned toward the front end of the compressor. A
spherical cavity is located on both inner faces of each
piston to receive the piston drive balls.
Both front and rear heads have an irregular shaped
casting web. These webs provide the necessary seals to
the surfaces of the discharge plates and prevent high
pressure vapor from flowing into the low pressure cavity.
Drive Balls
Suction Screen
The hardened steel drive balls have a micro-finish. They
are manufactured to a .0001 inch spherical tolerance and
a .6248 - .6250 inch diameter tolerance.
A fine mesh inlet (or suction) screen is located in the low
pressure cavity of the rear head. Its purpose is to stop
any material which could damage the compressor
mechanism.
Ball Seats
The bronze ball seats have one flat side, which contacts
the wobble plate, and one concave surface into which the
drive ball fits. Ten seats are provided in .0005 inch
thickness variations including a basic ZERO seat for
Heads
Suction Cross-Over Cover
The suction cross-over cover, with its neoprene seal is
pressed into the dove-tail cavity in the front and rear
cylinder castings to form a passage for the low pressure
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
S h a ft N u t
C lutch H ub R etain er
R ing
Spacer
C lutch H u b and D rive
Plate A ssem bly
Pulley and Bearing
R etain er Ring
Pulley Bearing
R etainer Ring
Pulley Bearing
Pulley
C oil Housing R etain er
R ing
C oil Housing
Compressor Shell
A bsorbent Sleeve
A bsorbent Sleeve
R etainer
O il D rain Plug and
Gasket
F ro n t Head-to-Shell
&quot; 0 ” Ring
16.
17.
18.
19.
2 0.
21.
22.
2 3.
24.
25.
2 6.
27.
28.
S h a ft Seal Seat
R etain er Ring
S h a ft Seal Seat
S h a ft Seal
S h a ft Seal Seat &quot; 0 ”
R ing
Compressor F ro n t
Head
F ro n t Discharge
Valve Plate
F ro n t S uction Reed
Valve
Discharge Crossover
T u b e F ro n t &quot; 0 ” Ring
and Spacer
M ainshaft F ro n t
Bearing
H ead Locating Pins
F ro n t C ylin d er H alf
F ro n t T h ru st Race
and Bearing Pack
S uction Crossover
Cover
D rive Key
44.
2 9.
30.
Discharge Crossover
31.
32.
Tube
Piston Ring
Piston F ro n t D rive
Ball
Piston F ro n t Ball
46.
3 3.
Seat
Piston
Piston R ear Ball Seat
Piston Rear D rive
47.
48.
49.
Ball
Piston R ing
D rive S h a ft and
W obble Plate
Assem bly
Rear T h ru s t Race and
Bearing Pack
Rear C y lin d e r H a lf
50.
51.
34.
35.
36.
37.
38.
39.
40.
41.
42.
4 3.
O il In le t T u b e &quot; 0 ”
Ring
O il In le t T u b e
M ainshaft Rear
Bearing
45.
52.
1A-31
Discharge Crossover
T u b e Rear &quot; 0 ” R ing
and Spacer
Rear S u c tio n Reed
Plate
Rear Discharge V alve
Plate
O il Pum p D rive Gear
O il Pum p D riven Gear
Rear H ead-to-S hell
&quot; 0 ” Ring
S train e r Screen
C om pressor Rear
Head
Superheat S w itc h ,
&quot; 0 ” R ing and
R etain er Ring
(G Models O n ly)
53.
High Pressure R elief
54.
V alve and &quot; 0 ” Ring
R ear H ead-to-S hell
R etain ing N uts
55.
C om pressor-toC onn ector &quot; 0 &quot; Ring
Fig. 3 5 -Six Cylinder Compressor -Exploded View
vapor to flow from the rear head of the compressor to
the front head.
Discharge Cross-Over Tube
Since the double acting pistons supply high pressure
vapor at both ends of the compressor the discharge tube
is needed to supply a path for the high pressure vapor to
pass from the front to the rear head. Should the cylinder
halves be separated during service operations a service
type discharge tube must be substituted.
Suction Reed Valves
A separate three-reed suction valve disc is assembled to
both front and rear heads. These reeds open when the
piston is on the intake portion of the stroke to allow the
low pressure vapor to flow into the cylinder. When the
piston reverses and begins the compression portion of its
stroke the reed valves close against their seats, thus
preventing the high pressure vapor from being forced
back into the low side of the system.
Discharge Valves
The two discharge valve plate assemblies act to direct
high pressure vapor into the head castings. When the
piston reverses into its suction stroke the high pressure
on the opposite side of the plate causes the reeds to close
thus maintaining the differential of pressure between
high and low pressure areas. The discharge plates
include the valves and the retainers which prevent the
LIGHT DUTY TRUCK SERVICE MANUAL
1A-32 HEATER A N D AIR C O N D IT IO N IN G
Refrigerant Lines
BALL SEATS USED
TO GIVE
.0005 TO .0010
TOTAL CLEARANCE
THRUST UNIT
CONTROLS
HEAD CLEARANCE
'* ^ 0 1 0
Special refrigerant hose lines are required to carry the
refrigerant liquid and vapor between the various system
components. The hose line with the smallest diameter is
called the high pressure liquid line. It is routed from the
condenser or receiver-dehydrator to the evaporator or
thermostatic expansion valve. The large diameter hose
line connecting the compressor and evaporator is the low
pressure vapor line. The large diam eter hose between the
compressor and condenser is the high pressure vapor
discharge line.
These hoses are constructed with a synthetic material
core covered with a woven metal mesh which is, in turn,
covered by a woven fabric and coated for extra
protection. This hose is so constructed to withstand the
extreme pressures and temperatures found in the modern
refrigeration system. None but special refrigerant type
hoses should be used.
THRUST UNIT CONTROLS
RUNNING CLEARANCE
.0005 TO .0015
Fig. 36- General Running Clearances
high pressure from distorting the valves during the
pressure stroke of the piston.
Head to Shell Seals
Two large diameter &quot;O &quot; rings internally seal the front
and rear heads to the shell. A chamfered edge on the
head castings creates a squeezing action between the
discharge valve plates, the compressor, and the inside
surface of the shell.
Compressor Connector
Compressor connectors, are attached to the compressor
rear head by means of a single bolt and lock washer. All
have inlet and outlet connections connected by a strap to
form an integral unit.
G Models have gauge fittings located on the muffler and
compressor inlet line. Motor Home Chassis unit fittings
are located on the inlet and outlet lines. C-K model
gauge fittings are located on the accumulator and
evaporator inlet line. All fittings are equipped with a
valve core.
Pressure Relief Valve
The pressure relief valve, located on the compressor rear
head, is simply a safety valve designed to open
automatically if the system pressure should reach a pre&shy;
determined level high enough to cause system damage.
After the pressure drops to a safe level the valve will
close. After such an occurrence, the system should be
thoroughly checked to discover and correct the cause of
the abnormal pressure increase, and then should be
purged, evacuated and charged.
All systems make use of swaged type connections (hose
to metal fittings) with metal to metal fittings being made
using &quot;O &quot; rings. Care must be taken when making these
connections that they not be turned down too tightly or
damage to the &quot;O &quot; rings may result.
Flexible refrigerant hoses should not be permitted to
contact the hot engine manifold nor should they be bent
into a radius of less than 10 times their diameter.
Muffler
A muffler, located in the high pressure line from the
compressor to the condenser, serves as a surge chamber
for high pressure gas to reduce the noise level of the
system while in operation. The muffler is actually a
welded portion of the compressor connector assembly. It
is found on all truck air conditioning systems.
Fan Slip Clutch
A special engine fan is used on most systems. It is an 18
inch five bladed fan, limited by means of a viscous
clutch to a maximum speed of 3200 rpm, regardless of
the speed of the engine. The silicone fluid in the clutch
transmits only enough torque to drive the fan at this
limited speed, thus avoiding excessive noise and power
consumption by the fan at higher engine speeds. A
temperature modulating device further limits fan speed
to 1000 rpm. until am bient tem perature at the
modulating device reaches 140&deg;F. at which time fan
speed will be allowed to increase to 3200 rpm. Some
adjustment of the modulating device is possible.
Condenser
In a properly charged system, the condenser delivers sub&shy;
cooled liquid. This is because all the vapor condenses
before the end of the condenser and the remaining
portion of the condenser subcools the liquid.
Receiver-Dehydrator (G and Motor Home
Chassis Models)
The receiver-dehydrator, serving as a reservoir for
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1A-33
storage of high pressure liquid produced in the
condenser, incorporates a screen sack filled with the
dehydrating agent.
The receiver-dehydrator, used prim arily as a liquid
storage tank, also functions to trap minute quantities of
moisture and foreign material which may have remained
in the system after installation or service operations. A
refrigerant sight glass is built into the receiverdehydrator to be used as a quick check of the state and
condition of charge of the entire system. The receiverdehydrator is mounted near the condenser.
Sight Glass (G and Motor Home Chassis Models)
While having no real function to perform in the system,
the sight glass is a valuable aid in determining whether
or not the refrigerant charge is sufficient and for
eliminating some guess work in diagnosing difficulties.
The sight glass, is built into the receiver-dehydrator
outlet connection and is designed and located so that a
shortage of refrigerant at this point will be indicated by
the appearance of bubbles beneath the glass. The dust
cap provided should be kept in place when the sight
glass is not in use.
Fig. 37- Expansion Valve
Thermostatic Expansion Valve (Fig. 37)
C-K Overhead, G Floor and Overhead and Motor Home
Chassis systems use a thermostatic expansion valve in
place of a float system.
The valve consists primarily of the power element, body,
actuating pins, seat and orifice. At the high pressure
liquid inlet, is a fine mesh screen which prevents dirt,
filings or other foreign matter from entering the valve
orifice.
When the valve is connected in the system, high pressure
liquid refrigerant enters the valve through the screen
from the receiver-dehydrator or condenser and passes on
to the seat and orifice. Upon passing through the orifice
the high pressure liquid becomes low pressure liquid.
The low pressure liquid leaves the valve and flows into
the evaporator core where it absorbs heat from the
evaporator core and changes to a low pressure vapor,
and leaves the evaporator core as such. The power
element bulb is clamped to the low pressure vapor line
just beyond the outlet of the evaporator (fig. 37).
The operation of the valve is quite simple. It is a matter
of controlling opposing forces produced by a spring and
the refrigerant pressures. For example: The pressure in
the power element is trying to push the seat away from
the orifice, while the adjusting spring is trying to force
the seat toward the orifice. These opposing pressures are
established in the design of the valve so that during idle
periods the adjusting spring tension and the refrigerant
pressure in the cooling coil are always greater than the
opposing pressure in the power element. Therefore, the
valve remains closed. When the compressor is started, it
will reduce the pressure and temperature of the
refrigerant in the cooling coil to a point where the vapor
pressure in the power element becomes the stronger. The
seat then moves off the orifice and liquid starts to flow
through the valve orifice into the cooling coil.
The purpose of the power element is to help determine
the quantity of liquid that is being metered into the
cooling coil. As the temperature of the low pressure line
changes at the bulb, the pressure of the vapor in the
power element changes, resulting in a change of the
position of the seat. For example, if the cooling coil gets
more liquid than is required, the temperature of the low
pressure line is reduced and the resultant lowering of the
bulb temperature reduces the pressure of the vapor in
the power element, allowing the seat to move closer to
the orifice. This immediately reduces the amount of
liquid leaving the valve. Under normal operation, the
power element provides accurate control of the quantity
of refrigerant to the cooling coil.
To employ our tire pump analogy once more for clarity,
it is the same situation that would exist if you were
inflating a tire with a very slow leak. Providing you
pumped the air into the tire as fast as it leaked out, you
would be able to m aintain pressure even though the air
would merely be circulating through the tire and leaking
out through the puncture.
Accumulator--C-K Models (Fig. 38)
The accumulator is located at the evaporator outlet. Its
most important function is not to &quot;accumulate&quot; although
this too is important. Its prim ary function is to separate
liquid retained from vapor, retain the liquid and release
the vapor to the compressor.
Thus, in an ideal accumulator with no oil bleed hole, and
LIGHT DUTY TRUCK SERVICE MANUAL
1A-34 HEATER A N D AIR C O N D IT IO N IN G
“ O ” RING
\
INLET
Fig. 39-Expansion Tube
The expansion tube is located in the enlarged portion of
the evaporator inlet line.
Thermostatic Switch
Fig. 38--Accumulator
in a correctly designed system, no liquid can get to the
compressor.
In an actual accumulator, there is some entrained liquid
in the vapor stream to the compressor. The measure of a
good accumulator is how well it separates vapor from
liquid and how little entrained liquid is released to the
compressor. Also, in an actual accumulator, an oil bleed
hole is required to prevent trapping of oil in the bottom
of the accumulator; this oil bleed hole bleeds some liquid
refrigerant as well.
Therefore, flow out of the accumulator to the compressor
consists mostly of vapor with the addition of entrained
liquid and liquid flow through the oil bleed hole.
A bag of desiccant (dehydrating agent) is located in the
base of the accumulator as a moisture collecting device.
NOTE: There is no sight glass in the
accumulator clutch cycle system.
Expansion Tube--C-K Models
Expansion tube flow rate depends on pressure difference
and on subcooling; however, the flow rate is more
sensitive to subcooling.
System temperature is controlled by running the
compressor intermittently, automatically turning it on
and off as necessary to m aintain proper temperatures.
The compressor is started and stopped through the use of
an electro-magnetic clutch and a thermostat affected by
variations in temperature.
The thermostatic switch incorporates a metallic tube
which contains a highly expansive gas. This tube is
inserted into the evaporator core (C-K Four-Season
System) or is located in the air stream as it leaves the
evaporator (all other systems). The tube leads to a
bellows operated switch. As air temperature rises, the gas
inside the tube expands, travels through the tube to the
bellows and closes the electrical switch which engages the
compressor clutch.
As soon as the compressor starts running, the
temperature begins to go down. As the air being cooled
gets colder, the gas in the thermostatic tube begins to
reduce the pressure on the switch bellows. This allows the
switch contacts to open and the compressor clutch
disengages.
Low Refrigerant Charge Protection System
C-K Models
The compressor discharge pressure switch performs the
function of shutting off the compressor when it senses
low refrigerant pressure. The switch is located in the
evaporator inlet line (high pressure). The switch
electrically is wired in series between the compressor
clutch and the master switch on the control. When the
switch senses low pressure it breaks contact and opens
the circuit to the compressor clutch, thus shutting off the
A /C system and preventing compressor failure or
seizure.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER AND AIR C O N D IT IO N IN G
The compressor discharge pressure switch also performs
the function of the ambient switch as the pressure at the
switch varies directly with ambient temperatures. The
compressor should not run below 25&deg;F. am bient or 37 psi
at the switch. The compressor should run in A /C modes
above 45&deg;F. ambient or 42 psi at the switch.
The switch interacts with other switches so that in an
A /C system where the compressor will not operate above
45&deg; ambient the following components should be checked
for continuity:
1. Compressor discharge pressure switch.
2. Master switch (on control head).
If both switches show proper continuity, check the
harness for shorts or improper ground conditions.
G Models
This low refrigerant charge protector system consists of a
superheat shutoff switch located in the rear head of the
compressor, connected in series by an electrical lead to a
thermal fuse.
During normal air conditioning system operating
conditions, current flows through the air conditioner
switch, the ambient switch, and through the thermal fuse
link to the clutch coil to actuate the compressor clutch.
Should a partial or total loss of refrigerant in the system
cause the superheat switch to sense low system pressure
and a high suction gas temperature, the superheat switch
contacts will close. When the contacts close, current flows
to energize the resistance type heater in the thermal fuse.
The resultant heat warms the fuse link to its specific melt
temperature, thus opening the circuit to the compressor
clutch coil. Compressor operation ceases and compressor
damage due to a loss of refrigerant charge is prevented.
The cause of the refrigerant loss must be corrected and
the system charged prior to replacing the thermal fuse.
The superheat switch does not have to be replaced when
it cycles and is reusable unless it is determined that the
switch is faulty.
CHEMICAL INGREDIENTS OF AN
AIR CONDITIONING SYSTEM
All systems involve metals, refrigerant, and oil which are
basic and essential. The desiccant, or dehydrating agent,
and another chemical ingredient, synthetic rubber,
makes it even more complex.
All of these ingredients have chemical properties which
are entirely different from each of the others. By proper
selection of the ingredients and controlled processes in
manufacture, plus careful servicing procedures, they can
be combined so that they provide many years of
satisfactory and trouble-free operation.
Only one undesirable element added or allowed to enter
the system can start a chain of chemical reactions which
upsets stability and interferes with the operation of the
unit.
1A-35
Chemical Instability and Refrigerant
System Failures
A sealed refrigerating system is a complex physicalchemical combination which is designed for stability
within certain operating limits. If these limits are
exceeded, many physical and chemical reactions occur to
the system. Since the results of these reactions within the
system cannot be easily removed, they build up into a
constantly accelerating vicious circle to eventually fail
the system.
Metals
In most cases, metals contribute to the decomposition of
R-12 and oil in varying amounts. All metals are attacked
by acids.
Each of the metals in common use in a system has been
selected for a specific reason; heat conductivity,
durability, strength, and chemical composition.
Under favorable conditions, the amount of decomposi&shy;
tion of Refrigerant-12 and oil produced by these metals
is negligible. If undersirable substances are added and
the temperature is increased, the rate of decomposition
and the production of harm ful acids increases
proportionally.
Refrigerant
The chemical properties of refrigerants are very
important factors in the stability of a system since the
refrigerant penetrates to every part of the unit.
Among the many desirable properties of R-12, is its
stability under operating conditions. While more stable
than the other refrigerants under the same conditions, it
can be caused to form harmful acids which will
eventually fail the system.
Oil
Oil is the most complex of all organic chemicals. Its
stability in a refrigerating system is dependent upon the
source of crude oil and its method of refining. A good
refrigeration oil must be free of sludge, gum-forming
substances and impurities such as sulphur. It must be
stabilized to resist oxidation and must have a high
degree of resistance to carbonization.
The chemical properties of the lubricating oil form
another very important consideration in the chemical
stability within the system. Like the refrigerant, it travels
to every part of the system.
The factory obtains the finest oils which have been
refined from the most desirable crudes. It is reprocessed
at the factory before it is charged into a system or
poured into a container for resale. Its viscosity and flash
point are checked and it is forced through many sheets
of filtering paper.
Even the containers in which it is poured for resale are
processed. It is the cleanest, dryest, and purest oil that is
humanly possible to make. Leaving the container
LIGHT DUTY TRUCK SERVICE MANUAL
1A-36 HEATER A N D AIR C O N D IT IO N IN G
uncapped even for a few minutes allows the oil to absorb
moisture from the air.
System failures can result if contaminated oil is added to
the system.
Desiccant (Dehydrating Agent)
An ideal desiccant must have the following
characteristics:
1. High capacity.
2. High efficiency.
3. Low tendency to powder.
4. Absorb moisture without reacting chemically with
it.
5. Allow refrigerant to flow through it with minimum
restriction.
6. Retain moisture at high temperature.
While some desiccants excel in several of the desirable
characteristics, they are unsatisfactory in others.
Activated Silica Alumina is a most satisfactory desiccant;
however, its ability to retain moisture is affected by its
temperature. As the temperature increases, its ability
decreases. This means that moisture which is retained at
a lower temperature may be put back into the system at
a higher temperature.
PRIMARY CAUSES OF SYSTEM FAILURES
Leaks
A shortage of refrigerant causes oil to be trapped in the
evaporator. Oil may be lost with the refrigerant at point
of leakage. Both of these can cause compressor seizure.
Oil circulates in the globules with the vapor. It leaves the
compressor by the action of the pistons and mixes with
the refrigerant liquid in the condenser. The oil then
enters the evaporator with the liquid and, with the
evaporator properly flooded, is returned to the
compressor through the low pressure line. Some of the
oil returns as globules in the vapor but more
importantly, it is swept as a liquid along the walls of the
tubing by the velocity of the vapor. If the evaporator is
starved, the oil cannot return in sufficient quantities to
keep the compressor properly lubricated.
High Temperature and Pressure
An increase in temperature causes an increase in
pressure. This accelerates chemical instability in clean
systems. Other results are brittle hoses, &quot;O &quot; ring gaskets,
and by-pass valve diaphragms with possible decomposi&shy;
tion, broken compressor discharge reeds, and seized
compressor bearings.
A fundamental law of nature accounts for the fact that
when a substance, such as a refrigerant, is increased in
temperature, its pressure is also increased.
Any chemical reactions caused by contaminants already
in the system are greatly accelerated as the temperature
increases. A 15&deg; rise in temperature doubles the chemical
action.
While temperature alone can cause the synthetic rubber
parts to become brittle and possibly to decompose, the
increased pressure can cause them to rupture or blow.
As the temperature and pressure increases, the stress and
strain on the discharge reeds also increases. This can
result in broken reeds. Due to the effect of the
contaminants caused by high temperature and pressure,
compressor bearings can be caused to seize.
High temperature and pressure is also caused by air in
the system.
Air in the System
Air results from a discharged system or careless servicing
procedures. This reduces system capacity and efficiency
and causes oxidation of oil into gum and varnish.
When a leak causes the system to become discharged, the
resulting vacuum within the system will cause air to be
drawn in. Air in a system is a non-condensable gas and
will build up in the condenser as it would in an air
compressor tank. The resultant heat produced will
contribute to the conditions discussed previously.
Many systems are contaminated and also reduced in
capacity and efficiency by careless servicing procedures.
Too frequently, systems which have been open to the
atmosphere during service operations have not been
properly purged or evacuated. Air is also introduced into
the system by unpurged gauge and charging lines.
Remember that any air in the system is too much air.
Poor Connections
Hose clamp type fittings must be properly made. Hose
should be installed over the sealing flanges and with the
end of the hose at the stop flange. The hose should never
extend beyond the stop flange. Locate the clamp
properly and torque as recommended. Be especially
careful that the sealing flanges are not nicked or scored
or a future leak will result.
When compression fittings are used, over-tightening can
cause physical damage to the &quot;O &quot; ring gasket and will
result in leaks. The use of torque and backing wrenches
is highly recommended. When making a connection with
compression fittings, the gaskets should always be first
placed over the tube before inserting it in the
connection.
Another precaution - inspect the fitting for burrs which
can cut the &quot;O &quot; ring.
Restrictions
Restrictions may be due to powdered desiccant or dirt
and foreign matter. This may result in starved
evaporator and loss of cooling, high temperature at the
bypass hose, or a seized compressor.
When the amount of moisture in a system sufficiently
exceeds the capacity of the desiccant, it can break down
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
the desiccant and cause it to powder. The powder passes
through the dehydrator screen with the refrigerant liquid
and is carried to the expansion valve screen. While some
of it may pass through the valve screen into the
evaporator, it may quickly build up to cause a restriction.
Due to the fact that sufficient oil then cannot be returned
to the compressor, it may seize.
1A-37
Dirt, which is any foreign material, may come from
cleaner residues, cutting, machining, or preserving oils,
metal dust or chips, lint or dust, loose rust, soldering or
brazing fluxes, paint or loose oxide scale. These can also
cause seized bearings by abrasion or wedging, discharge
and expansion valve failure, decomposition of refriger&shy;
ant and oil, or corrosion of metal parts.
many difficulties in refrigerating systems, in most
instances it is the presence of moisture in the system that
accelerates these conditions. It can be said, therefore,
that moisture is the greatest problem of all. The acids
that it produces, in combination with both the metals
and the refrigerant, causes dam aging corrosion. While
the corrosion may not form as rapidly with R-12 as with
some other refrigerants, the eventual formation is as
damaging.
If the operating pressure and temperature in the
evaporator is reduced to the freezing point, moisture in
the refrigerant can collect at the orifice of the expansion
valve and freeze. This temporarily restricts the flow of
liquid causing erratic cooling.
As previously mentioned, moisture in excess of the
desiccant’s capacity can cause it to powder.
Corrosion
Points to Remember
Dirt
Corrosion and its by-products can restrict valve and drier
screens, roughen bearing surfaces or hasten fatiguing of
discharge reeds. This can result in high temperature and
pressure, decomposition or leaks. In any event, this
means a damaged compressor.
From this, we can see the vicious circle that can be
produced in a refrigerating system to cause its failure.
Corrosion can be the indirect cause of leaks and leaks
can be the direct cause of corrosion. We can also see the
im portant role servicemen play in m aintaining chemical
stability.
The major cause of corrosion is moisture.
Moisture
Moisture is the greatest enemy of refrigerating systems.
Combined with metal, it produces oxide, Iron Hydroxide,
and Aluminum Hydroxide. Combined with R-12, it
produces Carbonic acid, Hydrochloric acid, and Hydro&shy;
fluoric acid. Moisture can also cause freeze-up of an
expansion valve and powdered desiccant.
Although high temperature and dirt are responsible for
Fig. 40-System Contaminants
That the inside of the refrigerant system is completely
sealed from the outside world. If that seal remains
broken at any point—the system will soon be damaged.
That complete and positive sealing of the entire system
is vitally im portant and that this sealed condition is
absolutely necessary to retain the chemicals and keep
them in a pure and proper condition.
That all parts of the refrigerant system are under
pressure at all times, whether operating or idle, and that
any leakage points are continuously losing refrigerant
and oil.
That the leakage of refrigerant can be so silent that the
complete charge may be lost without warning.
That refrigerant gas is heavier than air and will rapidly
drop to the floor as it flows from a point of leakage.
That the pressure in the system may momentarily
become as high as 480 lbs. per square inch.
That the total refrigerant charge circulates through the
entire system at least once each minute.
That the compressor is continually giving up some
lubricating oil to the circulating refrigerant and depends
upon oil in the returning refrigerant for continuous
replenishment. Any stoppage or major loss of refrigerant
will therefore damage the compressor.
That the extreme internal dryness of a properly
processed system is a truly desert condition, with the
drying material in the receiver or accumulator holding
tightly onto the tiny droplets of residual moisture.
That the attraction of the drying m aterial for moisture is
so powerful that if the receiver or accumulator is left
open, moisture will be drawn in from the outside air.
That water added to the refrigerant will start chemical
changes that can result in corrosion and eventual
breakdown of the chemicals in the system. Hydrochloric
acid is one result of an R-12 mixture with water.
That air in the refrigerant system may start reactions
that can cause malfunctions.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-38 HEATER A N D AIR C O N D IT IO N IN G
That the drying agent in the receiver or accumulator is
Activated Silica Alumina.
That the inert gas in the expansion valve-capillary line is
carbon dioxide.
SYSTEM CONTROLS
Four-Season System (C-K Models) - Fig. 41
The system selector level (air control lever) determines the
mode of operation: OFF, A/C, VENT, HEATER, BILEVEL
or DEF. When the system selector lever is placed in the A/C,
BI-LEVEL or DEF positions, electrical circuit connection is
made to the compressor clutch through the control panel
switch and the discharge pressure switch. If the switch is
closed (ambient temperature above 40&deg;F.), the compressor
will run. In the OFF, VENT or HEATER positions, the com&shy;
pressor is not energized.
recirculation of interior air (recirc. operation) provides a
source of fast cool down of interior temperatures.
Fan Switch
The blower (FAN) switch provides a means of selecting
the amount of airflow from the system by regulating the
speed of the blower motor. There are, however,
limitations to the control of blower speed. To provide
constant ventilation, the blower motor electrical circuitry
prevents the blower motor from being shut off when the
ignition switch is on. Therefore, the blower speeds
available are HI, LO and two medium speeds.
The control panel also has a &quot;recirc. override&quot; switch
which overrides the blower speed switch and automati&shy;
cally provides HI blower speed when the system selector
lever is in A /C and the temperature lever is set to full
COLD.
Overhead System (C-K Models)
The system selector lever also determines the direction of
outlet air flow. Moving the lever from mode to mode
varies the position of a rotary vacuum valve on the
control. The position of the vacuum valve will supply
vacuum to, or vent, vacuum diaphragms which position
the upper and lower mode and defroster air doors in the
selector duct assembly. The position of these air doors
determines if output air flow is from heater outlet
(OFF), the heater outlet with slight air flow from
defroster nozzles (HEATER), heater and A /C outlets
(VENT), A /C outlet only (A/C), heater, A /C and
defroster outlets (BI-LEVEL), or the defroster nozzles
with slight air flow from the heater outlet (DEF).
Temperature Control
The temperature lever determines the temperature of
outlet airflow by positioning the temperature door in the
selector duct assembly, through the motion of a bowden
cable linking the control panel lever to the temperature
door. In addition, the temperature lever is connected to a
second vacuum valve on the control panel.
The vacuum valve supplies vacuum to the air inlet
diaphragm through the system selector lever rotary
vacuum valve. When the system is in A /C mode and the
temperature lever is at full COLD, the air inlet door is
positioned to reduce the supply of outside air to the
system from 100% to approximately 20%. The remainder
of the air input (80%) to the A /C system is then taken
from the interior of the passenger compartment. This
HI
1:
l
mS3
#
11
8
•
10
FAN
Off
■
r
A/C
■ ..
VINT
•
HEMER
m
Bl LEVEL
m
- .......
COID
^
- ....
This system operates in conjunction with the FourSeason System. Since refrigerant flow is controlled by the
front system, the only control provided for on the
overhead system is a three-speed fan switch (LOW),
MED, HI). The fan switch is mounted in the instrument
panel, to the right of the steering column (fig. 42).
In the OFF position, the blower is inoperative; however,
refrigerant is circulating in the system if the FourSeason System is ON. In any of the three blower
positions (LOW, MED, HI), the blower will be operative
regardless if the Four-Season System is ON.
NOTE: To obtain maximum cooling, the
Four-Season System should be on A/C,
temperature lever on COLD, blower switch
on HI and the overhead unit blower switch
should be on HI.
Floor Mounted System (G Models)
Controls for the front floor mounted system consist of a
Off
m
HOI
*1
Fig. 41-Four-Season System Controls (C-K Models)
Fig. 42-Overhead Unit Control (C-K Models)
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-39
Fig. 44- Motor Home Unit Control
Fig. 43--Floor and Overhead Controls (G Models)
temperature knob and a three speed blower switch. The
controls are mounted on the blower-evaporator cover to
the right of the driver (fig. 43).
The temperature knob is used to control the degree of
cooling desired. Fully clockwise at CITY provides
maximum cooling while turning the knob to HIWAY
provides adequate cooling for highway operation.
The three speed blower fan switch (LOW-MED-HI) is
used to control the quantity of air flow.
NOTE: Reduced cooling and freezing of the
evaporator could be encountered when
operating at highway speeds with the controls
at the &quot;CITY&quot; setting.
Overhead System (G Models)
This system operates in conjunction with the front floor
mounted system. Since refrigerant is controlled by the
front system the only control provided on the rear
overhead system in a three speed blower switch (fig. 43).
In the OFF position, the blower is inoperative; however,
refrigerant is circulating in the system if the front system
in ON. To operate the rear overhead system, simply
select the desired blower speed (LOW, MED, HI).
NOTE: The rear unit will not operate unless
the front unit is calling for cooling.
Dash Mounted Unit (Motor Home Chassis
Units)
This system is self contained and is mounted below the
dash by the body manufacturer. System controls consist
of an AIR knob and TEMP knob located in the center of
the unit face plate (fig. 44).
Air Knob
Turning the AIR knob clockwise operates a three speed
(LOW-MED-HI) blower motor.
Temp Knob
This knob is used to control the degree of cooling
desired. Fully clockwise at CITY provides maximum
cooling, while turning the knob to HIWAY provides
adequate cooling for highway operation.
NOTE: Reduced cooling could be encoun&shy;
tered when operating at highway speeds with
the controls at the CITY setting. The heater
must be fully off to obtain maximum cooling.
GENERAL IN FO R M A TIO N
In any vocation or trade, there are established
procedures and practices that have been developed after
many years of experience. In addition, occupational
hazards may be present that require the observation of
certain precautions or use of special tools and
equipment. Observing the procedures, practices and
precautions of servicing refrigeration equipment will
greatly reduce the possibilities of damage to the
customers’ equipment as well as virtually eliminate the
element of hazard to the serviceman.
PRECAUTIONS IN HANDLING
REFRIGERANT-12
Refrigerant-12 is transparent and colorless in both the
gaseous and liquid state. It has a boiling point of 21.7&deg;F
below zero and, therefore, at all normal temperatures
and pressures it will be a vapor. The vapor is heavier
than air, and is noninflammable, nonexplosive, nonpoisonous (except when in contact with an open flame) and
noncorrosive (except when in contact with water).
WARNING: The following precautions in
handling R-12 should be observed at all
times.
• If it is ever necessary to transport or carry a cylinder
or can of refrigerant in a car, keep it in the luggage
compartment. Refrigerant should not be exposed to
the radiant heat from the sun since the resulting
increase in pressure may cause the safety valve to
release or the cylinder or can to burst.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-40 HEATER A ND AIR C O N D IT IO N IN G
• Cylinders or disposable cans should never be
subjected to high tem perature when adding
refrigerant to the system. In most instances, heating
the cylinder or can is required to raise the pressure
in the container higher than the pressure in the
system during the operation. It would be unwise to
place the cylinder on a gas stove, radiator or use a
blow torch while preparing for the charging
operation, for a serious accident can result.
Remember, high pressure means that great forces
are being exerted against the walls of the container.
A bucket of warm water, not over 125&deg;F, or warm
wet rags around the container is all the heat that is
required.
• Do not weld or steam clean on or near the system.
Welding or steam cleaning can result in a dangerous
pressure buildup in the system.
• Discharging large quantities of R-12 into a room
can usually be done safely as the vapor would
produce no ill effects; however, in the event of an
accidental rapid discharge of the system, it is
recommended that inhalation of large quantities of
R-12 be avoided. This caution is especially
important if the area contains a flame producing
device such as a gas heater. While R-12 normally is
nonpoisonous, heavy concentrations of it in contact
with a live flame will produce a toxic gas. The same
gas will also attack all bright metal surfaces.
• Protection of the eyes is of vital importance! When
working around a refrigerating system, an accident
may cause liquid refrigerant to hit the face. If the
eyes are protected with goggles or glasses, no serious
damage can result. Just remember, any R-12 liquid
that touches you is at least 21.7&deg;F below zero. If
R-12 liquid should strike the eyes, here is what to
do:
1. Keep calm.
2. Do not rub the eyes. Splash the affected area
with quantities of cold water to gradually get the
temperature above the freezing point. The use
of mineral, cod liver or an antiseptic oil is
important in providing a protective film to
reduce the possibility of infection.
3. As soon as possible, call or consult an eye
specialist for immediate and future treatment.
PRECAUTIONS IN HANDLING
REFRIGERANT LINES
CAUTIO N: The following precautions should
be observed when handling refrigerant lines:
• All metal tubing lines should be free of kinks,
because of the restriction that kinks will offer to the
flow of refrigerant. The refrigeration capacity of the
entire system can be greatly reduced by a single
kink.
• The flexible hose lines should never be bent to a
•
•
•
•
radius of less than 10 times the diam eter of the
hose.
The flexible hose lines should never be allowed to
come within a distance of 2-1/2&quot; of the exhaust
manifold.
Flexible hose lines should be inspected at least once
a year for leaks or brittleness. If found brittle or
leaking they should be replaced with new lines.
Use only new lines that have been sealed during
storage.
When disconnecting any fitting in the refrigeration
system, the system must first be discharged of all
refrigerant. However, proceed very cautiously
regardless of gauge readings. Open very slowly,
keeping face and hands away so that no injury can
occur if there happens to be liquid refrigerant in the
line. If pressure is noticed when fitting is loosened,
allow it to bleed off as described under &quot;Purging the
System&quot; in this section.
WARNING: Always wear safety goggles when
opening refrigerant lines.
• In the event any line is opened to atmosphere, it
should be immediately capped to prevent entrance
of moisture and dirt.
• The use of the proper wrenches when making
connections on &quot;O &quot; ring fittings is important. The
use of im proper wrenches may damage the
connection. The opposing fitting should always be
backed up with a wrench to prevent distortion of
connecting lines or components. When connecting
the flexible hose connections it is important that the
swaged fitting and the flare nut, as well as the
coupling to which it is attached, be held at the same
time using three different wrenches to prevent
turning the fitting and dam aging the ground seat.
• &quot;O &quot; rings and seats must be in perfect condition. A
burr or piece of dirt may cause a leak.
• Sealing beads on hose clamp connections must be
free of nicks and scratches to assure a perfect seal.
MAINTAINING CHEMICAL STABILITY IN
THE REFRIGERATION SYSTEM
The metal internal parts of the refrigeration system and
the refrigerant and oil contained in the system are
designed to remain in a state of chemical stability as
long as pure R-12 and uncontaminated refrigeration oil
is used in the system.
However, when abnormal amounts of foreign materials,
such as dirt, air or moisture are allowed to enter the
system, the chemical stability may be upset. When
accelerated by heat, these contaminants may form acids
and sludge and eventually cause the breakdown of
components within the system. In addition, contaminants
may affect the temperature-pressure relationship of R-12,
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
resulting in im proper operating tem perature and
pressures and decreased efficiency of the system.
CAUTIO N: The following general practices
should be observed to ensure chemical stability
in the system:
• Whenever it becomes necessary to disconnect a
refrigerant or gauge line, it should be immediately
capped. Capping the tubing will also prevent dirt
and foreign matter from entering.
• Tools should be kept clean and dry. This also
includes the gauge set and replacement parts.
• When adding oil, the container should be exception&shy;
ally clean and dry due to the fact that the
refrigeration oil in the container is as moisture-free
as it is possible to make it; therefore, it will quickly
absorb any moisture with which it comes in contact.
For this same reason the oil container should not be
opened until ready for use and then it should be
capped immediately after use.
• When it is necessary to open a system, have
everything you will need ready and handy so that as
little time as possible will be required to perform
the operation. Don’t leave the system open any
longer than is necessary.
• Finally, after the operation has been completed and
the system sealed again, air and moisture should be
evacuated from the system before recharging.
J-8393 CHARGING STATION
The J-8393 Charging Station is a portable assembly of a
vacuum pump, refrigerant supply, gauges, valves, and
most important, a five (5) pound metering refrigerant
charging cylinder. The use of a charging cylinder
eliminates the need for scales, hot water pails, etc.
The chief advantage of this unit is savings. A very
definite savings in refrigerant and time can be obtained
by using this unit. Since the refrigerant is metered into
the system by volume, the correct amount may be added
to the system. This, coupled with the fact that the unit
remains &quot;plum bed&quot; at all times and thus eliminates loss
of refrigerant in purging of lines and hooking-up,
combines to enable the operator to get full use of all
refrigerant purchased.
All evacuation and charging equipment is hooked
together in a compact portable unit (fig. 45). It brings air
conditioning service down to the basic problem of
hooking on two hoses, and manipulating clearly labeled
valves.
This will tend to ensure that the job will be done without
skipping operations. As a result, you can expect to save
time and get higher quality work, less chance of an over
or under charge, thus reducing comebacks.
The pump mount is such that the dealer may use his own
vacuum pump. The gauges and manifold are in common
LOW PRESSURE
CONTROL ( l)
1A-41
HIGH PRESSURE
CONTROL ( 2)
VACUUM
CONTROL
REFRIGERANT
CONTROL
(3)
(4)
LOW PRESSURE
GAUGE LINE
HiGH PRESSURE
GAUGE LINE
5 LB. CHARGING
' CYLINDER
-LEAK
DETECTOR
REFRIGERANT
•CONTROL VALVE
Fig. 4 5 -J-8393 Charging Station
use. Thus a current air conditioning dealer can use the
equipment on hand and avoid duplication.
GAUGE SET
The gauge set (fig. 46) is an integral part of the J-8393
Charging Station. It is used when purging, evacuating,
charging or diagnosing trouble in the system. The gauge
at the left is known as the low pressure gauge. The face
is graduated into pounds of pressure and, in the opposite
1
2
LOW PRESSURE
CONTROL
HIGH PRESSURE
CONTROL
4
3
REFRIGERANT
CONTROL
VACUUM
CONTROL
Fig. 46 -Gauge Set
LIGHT DUTY TRUCK SERVICE MANUAL
1A-42 HEATER A N D AIR C O N D IT IO N IN G
direction, in inches of vacuum. This is the gauge that
should always be used in checking pressures on the low
pressure side of the system. When all parts of the system
are functioning properly the refrigerant pressure on the
low pressure side never falls below 0 pounds pressure.
However, several abnormal conditions can occur that will
cause the low pressure to fall into a partial vacuum.
Therefore, a low pressure gauge is required.
The high pressure gauge is used for checking pressures
on the high pressure side of the system.
The hand shutoff valves on the gauge manifold do not
control the opening or closing off of pressure to the
gauges. They merely close each opening to the center
connector and to each other. During most diagnosing
and service operation, the valves must be closed. Both
valves will be open at the same time during purging,
evacuating and charging operations.
The charging station provides two flexible lines for
connecting the gauge set to the system components.
FIVE AMP
TIME DELAY
FUSE
CORD TO
110 AC SOURCE
PUMP
INLET
PUMP DISCHARGE
OUTLET
VACUUM PUMP
A vacuum pump should be used for evacuating air and
moisture from the air conditioning system.
The vacuum pump (fig. 47), is a component part of
Charging Station J-8393, described previously.
CAU TIO N : The following precautions should
be observed relative to the operation and
maintenance o f this pump:
• Make sure dust cap on discharge outlet of
vacuum pump is removed before operating.
• Keep all openings capped when not in use to
avoid moisture being drawn into the system.
• Oil should be changed after every 250 hours of
normal operation.
To change oil, simply unscrew hex nut located on
back side of pump, tilt backward and drain out
oil (fig. 47). Recharge with 8 ounces of vacuum
pump oil Frigidaire 150 or equivalent. If you
desire to flush out the pump, use this same type
clean oil. Do not use solvent. Im proper
Lubrication will shorten pump life.
• If this pump is subjected to extreme or
prolonged cold, allow it to remain indoors until
oil has reached approximate room temperature.
Failure to warm oil will result in a blown fuse.
• A five ampere time delay cartridge fuse has been
installed in the common line to protect the
windings of the compressor. The fuse will blow
if an excessive load is placed on the pump. In the
event the fuse is blown, replace with a five
ampere time delay fuse. Do not use a substitute
fuse as it will result in damage to the starting
windings.
Fig. 47-Vacuum Pump
• If the pump is being utilized to evacuate a burntout system, a filter must be connected to the
intake fitting to prevent any sludge from
contaminating the working parts, which will
result in malfunction of the pump.
• Do not use the vacuum pump as an air
compressor.
LEAK TESTING THE SYSTEM
Whenever a refrigerant leak is suspected in the system or
a service operation performed which results in disturbing
lines or connections, it is advisable to test for leaks.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
Common sense should be the governing factor in
performing any leak test, since the necessity and extent
of any such test will, in general, depend upon the nature
of the complaint and the type of service performed on
the system.
Leak Detector
Tool J-6084 (fig. 48) is a propane gas-burning torch
which is used to locate a leak in any part of the system.
Refrigerant gas drawn into the sampling tube attached
to the torch will cause the torch flame to change color in
proportion to the size of the leak. Propane gas fuel
cylinders used with the torch are readily available
commercially throughout the country.
W ARNING: Do not use lighted detector in
any place where combustible or explosive
gases, dusts or vapors may be present.
Operating Detector
1. Determine if there is sufficient refrigerant in the
system for leak testing.
2. Open control valve only until a low hiss of gas is
heard, then light gas at opening in chimney.
3. Adjust flame until desired volume is obtained. This
is most satisfactory when blue flame is approx&shy;
imately 3/8&quot; above reactor plate. The reaction plate
will quickly heat to a cherry red.
4. Explore for leaks by moving the end of the
1A-43
sampling hose around possible leak points in the
system. Do not pinch or kink hose.
NOTE: Since R-12 is heavier than air, it is
good practice to place open end of sampling
tube immediately below point being tested,
particularly in cases of small leaks.
W ARNING: Do not breathe the fumes that
are produced by the burning of R-12 gas in
the detector flame, since such fumes can be
toxic in large concentrations.
5. Watch for color changes. The color of the flame
which passes through the reaction plate will change
to green or yellow-green when sampling hose draws
in very small leaks of R-12. Large leaks will be
indicated by a change in color to a brilliant blue or
purple; when the sampling hose passes the leaks,
the flame will clear to an almost colorless pale-blue
again. Observations are best made in a semi&shy;
darkened area. If the flame remains yellow when
unit is removed from leak, insufficient air is being
drawn in or the reaction plate is dirty.
NOTE: A refrigerant leak in the high
pressure side of the system may be more
easily detected if the system is operated for a
few minutes, then shut off and checked
immediately (before system pressures equal&shy;
ize). A leak on the low pressure side may be
more easily detected after the engine has
been shut off for several minutes (system
pressures equalized); this applies particularly
to the front seal.
AVAILABILITY OF REFRIGERANT-12
Refrigerant-12 is available in 30 lb. and in 15 oz.
disposable containers.
Normally, air conditioning systems are charged making
use of the J-8393 Charging Station which uses the 30 lb.
container. Evacuating and charging procedures are noted
later in this section.
The 15 oz. disposable cans are generally used for
miscellaneous operations such as flushing.
W ARNING: The following precautions should
be observed when adding refrigerant to a
system using 15 oz. disposable cans:
Fig. 48-Leak Detector
1. Do not charge while compressor system is hot.
2. Empty container completely before disposing.
3. Use opening valves designed for use with container
- follow valve m anufacturer’s directions carefully.
4. Always use pressure gauges before and during
charging.
5. NEVER connect on high pressure side of system or
LIGHT DUTY TRUCK SERVICE MANUAL
1A-44 HEATER A N D AIR C O N D IT IO N IN G
to any system having a pressure higher than
indicated on refrigerant containers.
6. If inexperienced, seek professional assistance.
COMPRESSOR OIL
Special refrigeration lubricant should be used in the
system. This oil is as free from moisture and
contaminants as it is possible to attain by human
processes. This condition should be preserved by
immediately capping the bottle when not in use.
See &quot;Air Conditioning System Capacities&quot; for the total
system oil capacity.
Due to the porosity of the refrigerant hoses and
connections, the system refrigerant level will show a
definite drop after a period of time. Since the
compressor oil is carried throughout the entire system
mixed with the refrigerant, a low refrigerant level will
cause a dangerous lack of lubrication. Therefore the
refrigerant charge in the system has a definite tie-in with
the amount of oil found in the compressor and an
insufficient charge may eventually lead to an oil build-up
in the evaporator.
COMPRESSOR SERIAL NUMBER
The compressor serial number is located on the serial
number plate on top of the compressor. The serial
number consists of a series of numbers and letters. This
serial number should be referenced on all forms and
correspondence related to the servicing of this assembly.
INSPECTION A N D PERIODIC SERVICE
PRE-DELIVERY INSPECTION
1. Check that engine exhaust in suitably ventilated.
2. Check the belt for proper tension.
3. With controls positioned for operation of the
system, operate the unit for five minutes at
approximately 2000 rpm. Observe the clutch pulley
bolt to see that the compressor is operating at the
same speed as the clutch pulley. Any speed
variation indicates clutch slippage.
4. Before turning off the engine, check refrigerant
charge (see &quot;Refrigerant Quick Check Procedure&quot;).
5. Check refrigerant hose connections:
&quot; 0 &quot; Ring Connections-- Check torque of fittings as
charted later in this section under &quot;Refrigerant Line
Connections;&quot; retorque if required. Leak test the
complete system.
6. If there is evidence of an oil leak, check the
compressor to see that the oil charge is satisfactory.
NOTE: A slight amount of oil leakage at the
compressor front seal is considered normal.
7. Check the system controls for proper operation.
6000 MILE INSPECTION
1. Check unit for any indication of a refrigerant leak.
2. If there is an indication of an oil leak, check the
compressor for proper oil charge.
NOTE: A slight amount of oil leakage at the
compressor front seal is considered normal.
3. Check refrigerant charge (see &quot;R efrigerant Quick
Check Procedure&quot;).
4. Tighten the compressor brace and support bolts and
check the belt tension.
5. Check refrigerant hose connections as in Step 5 of
&quot;Pre-Delivery Inspection.&quot;
PERIODIC SERVICE
• Inspect condenser regularly to be sure that the fins
are not plugged with leaves or other foreign
material.
• Check evaporator drain tubes regularly for dirt or
restrictions.
• At least once a year, check the system for proper
refrigerant charge and the flexible hoses for
brittleness, wear or leaks.
• Every 6000 miles check for low refrigerant level.
• Check belt tension regularly.
EVACUATING A N D C HA RG IN G PROCEDURES
AIR CONDITIONING SYSTEM CAPACITY
See Capacity Chart on Page 1A-45.
INSTALLING CHARGING STATION
1. High and low pressure gauge line fittings are
provided in the air conditioning system for
attaching the Charging Station.
C-K Models~The low pressure fitting is located on
the accumulator and the high pressure fitting on the
evaporator inlet line.
G Models-The low pressure fitting is on the
compressor inlet line and the high pressure fitting
on the muffler.
Motor Home Chassis~The low pressure fitting is on
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
Refrigerant
Charge
Four-Season System
(C-K Models)
Overhead System
(C-K-G Models)
Floor Mounted System
(G Models)
Dash Mounted Unit
(Motor Home Chassis)
2.
3.
4.
5.
6.
3 lbs.
1A-45
Oil Charge
10 oz. 525 Viscosity
REFRIGERANT LINE
LOW PRESSURE
ACCUMULATOR
(CONDENSER TO
M|G n PRESSURE
5 lbs. 4 oz. 13 oz. 525 Viscosity
3 lbs. 4 oz. 10 oz. 525 Viscosity
3 lbs. 4 oz. 10 oz. 525 Viscosity
the compressor inlet line and the high pressure
fitting is on the compressor outlet line.
W ith the engine stopped, remove the caps from the
cored valve gauge fittings.
Install Gauge Adapters J-5420 and J-9459 onto the
high and low pressure lines of the Charging
Station.
Be certain all the valves on the Charging Station
are closed.
Connect the high pressure gauge line to the high
pressure fitting on the system.
Referring to Figure 49, turn the high pressure
control (2) one turn counterclockwise (open). Crack
open the low pressure control (1) and allow
refrigerant gas to hiss from the low pressure gauge
line for three seconds, and then connect the low
pressure line to the low pressure fitting on the
system.
W ARNING: When removing the gauge lines
from the fittings, be sure to remove the
adapters from the system fittings rather than
the gauge lines from the adapter.
7. The system is now ready for purging or
performance testing.
PURGING THE SYSTEM
In replacing any of the air conditioning components, the
system must be completely purged or drained of
refrigerant. The purpose is to lower the pressure inside
the system so that a component part can be safety
removed.
1. With the engine stopped, install high and low
pressure lines of Charging Station gauge set to the
proper high and low pressure gauge fittings (See
&quot;Installing The Charging Station&quot;).
CAUTIO N: Before installing lines, be sure that
all four controls on the gauge set are closed.
2. Disconnect vacuum line at Charging Station
Fig. 49--Charging Schematic-C-K Truck Shown
vacuum pump and put the line in a covered can as
shown in Figure 50.
NOTE: An empty 3 lb. coffee can with a
plastic cover which has been cross-slit (X’ed),
to allow hose entry, works well for this
purpose.
3. Fully open high (2) and low (1) pressure control
valves, and allow refrigerant to purge from system
at a rapid rate into the covered can.
4. Oil loss will be minimal. It may be added to the
system during evacuation as described later.
5. Toward the end of the purge stage, Tool J-24095
should be flushed with refrigerant to eliminate
possible contamination.
a. Disconnect refrigerant line at supply tank.
b. Flush Tool J-24095 by cracking open valve on
refrigerant tank. After flushing for approx&shy;
imately three seconds, close valve.
c. Temporarily refasten the tool.
d. Reconnect refrigerant line to supply tank.
EVACUATING AND CHARGING THE
SYSTEM
GENERAL NOTE: In all evacuating procedures
shown below, the specification of 28-29 inches of
Mercury vacuum is used. These figures are only
attainable at or near Sea Level Elevation. For each
1000 feet above sea level where this operation is
being performed, the specifications should be
lowered by 1 inch. Example: at +5000 ft. elevation,
LIGHT DUTY TRUCK SERVICE MANUAL
1A-46 HEATER A N D AIR C O N D IT IO N IN G
only 23 to 24 inches of vacuum can normally be
obtained.
Whenever the air conditioning system is open for any
reason, it should not be put into operation again until it
has been evacuated to remove air and moisture which
may have entered the system.
The following procedures are based on the use of the
J-8393 Charging Station:
Adding Oil
If necessary, refrigeration oil may be added to the
system by the following method:
1. Install charging station and purge system as
previously described.
2. After system has been purged, connect the vacuum
line to the vacuum pump.
3. Measure oil loss collected as a result of purging the
system.
a. Disconnect the Charging Station low pressure
line. Install Tool J-24095 (with valve closed)
onto the system low pressure fitting. Insert pick&shy;
up tube into graduated container of clean
refrigerant oil (fig. 51).
NOTE: Tool J-24095 will hold 1/2 of an
ounce of oil in the tool itself. So if 1 oz. has
to be added, the level of the oil in the bottle
should decrease 1-1/2 ounces to add 1 oz. to
the system.
CAUTIO N: When removing the gauge lines
from the fittings, be sure to remove the adapters
J-8393
CHARGING
STATION
TO HIGH
PRESSURE
FITTING
OIL
COLLECTING
CAN
Fig. 50-Collecting Refrigerant Oil During &quot;Purging&quot;
from the system fittings rather than the gauge
lines from the adapter.
b. Turn on vacuum pump, and open vacuum
control valve (slowly open high pressure side of
manifold gauge set to avoid forcing oil out of
refrigerant system and pump).
NOTE: When valve on Tool J-24095 is
opened, the vacuum applied to the discharge
side of the system will suck oil into system
from container. Therefore, close observation
of oil level in the container is necessary.
c. Note level of oil in container. Open valve on oil
adding tool until oil level in container is reduced
by an amount equal to that lost during discharge
of system plus 1/2 ounce, then close valve. Take
care not to add more oil than was lost
d. Disconnect and cap Tool J-24095 and reinstall
charging station low pressure line to the system.
Open low pressure valve (1).
Evacuation
After oil has been added to the system (as outlined
above), run pump until 28-29 inches vacuum is obtained
(See General Note under &quot;Evacuating and Charging the
System&quot;). Continue to run pump for 10 minutes after the
system reaches 28-29 inches vacuum.
NOTE: If 28-29 inches cannot be obtained,
close Vacuum Control Valve (3) and shut off
vacuum pump. Open Refrigerant Control
Valve (4) and allow 1/2 pound of R-12 to
enter system. Locate and repair all leaks.
Purge this 1/2 pound and re-evacuate for 10
minutes.
1. During the ten minute evacuation period, prepare
for charging the system by filling the charging
cylinder as follows:
a. Open valve on bottom of charging cylinder
allowing refrigerant to enter cylinder.
NOTE: It will be necessary to close bleed
valve periodically to allow boiling to subside
to check level in the sight glass of Charging
Station cylinder.
b. Bleed cylinder valve on top (behind control
panel) as required to allow refrigerant to enter.
When refrigerant reaches desired level (see
&quot;System Capacity&quot;), close valve at bottom of
cylinder and be certain bleed valve is closed
securely.
2. Continue to evacuate for rem ainder of 10 minute
period.
3. Turn hand shut-off valves at low and high pressure
gauges of gauge set to full clockwise position with
vacuum pump operating, then stop pump. Carefully
check low pressure gauge for approximately two
minutes to see that vacuum remains constant. If
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
vacuum reduces, it indicates a leak in the system or
gauge connections; locate and repair all leaks.
Charging the System
1. Only after evacuating as above, is system ready for
charging. Note reading on sight glass of charging
cylinder. If it does not contain a sufficient amount
of refrigerant for a full charge, fill to the proper
level.
2. With High and Low Pressure Valves (1 and 2) open,
close Vacuum Control Valve (3), turn off vacuum
pump, open refrigerant control valve (4) and allow
refrigerant to enter system.
NOTE: If the charge will not transfer
completely from the station to the system,
close the high pressure valve at the gauge set,
set the air conditioning controls for cooling,
check that the engine com partment is clear of
obstructions, and start the engine. Compres&shy;
sor operation will decrease the low side
pressure in the system.
System is now charged and should be checked as
outlined below:
Checking System Operation
1. Operate system for a maximum of five minutes at
maximum cooling, high blower speed and with
engine operating at 2000 RPM (exhaust should be
vented if inside).
2. When system is stabilized, the pressure gauges on
J -2 4 0 9 5
TO LOW
PRESSURE
FITTING
CHARGING STATION
HIGH PRESSURE LINE
REFRIGERANT
OIL
TO HIGH
PRESSURE
FITTING
Fig. 51-Adding Refrigeration Oil Using Tool J-24095
1A-47
the charging station should read pressures corre&shy;
sponding to values listed under PERFORMANCE
DATA.
3. When correct system pressures are observed, check
system charge as described under &quot;Refrigerant
Quick Check Procedure&quot;.
4. Feel outlet air distribution to ensure that cold air is
being distributed.
5. Disconnect gauge lines and cap fittings.
CAUTIO N: When removing gauge lines from
fittings, be sure to remove the adapters from the
fittings rather than the gauge lines from the
adapters.
PERFORMANCE TEST
Under normal circumstances, it will not be necessary to
Performance Test a system as outlined below; however,
in certain instances, the following procedure may be
advantageous in diagnosing system malfunction.
The following fixed conditions must be adhered to in
order to make it possible to compare the performance of
the system being tested with the standards below:
1. Doors and windows closed. (Vehicle inside or in
shade.)
2. Hood up and engine exhaust suitably ventilated.
3. Vehicle in NEUTRAL with engine running at 2000
rpm.
4. Air Conditioning controls set for • Maximum cooling.
• High blower speed
5. TEMP control set at &quot;CO LD &quot; and all air
conditioning outlets open.
6. Gauge set installed.
7. System settled out (run-in approxim ately 10
minutes).
8. A thermometer placed in front of vehicle grille and
another in the right hand diffuser outlet.
NOTE: On Overhead Systems, place a third
thermometer in the rear unit center outlet.
9. An 18&quot; fan placed in front of the vehicle and
blowing into the condenser.
NOTE: Higher temperatures and pressures
will occur at higher ambient temperatures. In
areas of high humidity it is possible to have
thermometer and gauge readings approach
but not reach the figures listed in the
performance tables and still have a satisfac&shy;
tory operating unit. However, it is im portant
to remember that low pressure has a direct
relationship to nozzle outlet temperature. If
pressure is too low, ice will gradually form on
the evaporator fins, restricting air flow into
LIGHT DUTY TRUCK SERVICE MANUAL
1A-48 HEATER A N D AIR C O N D IT IO N IN G
the passenger area and resulting in insuffi&shy;
cient or no cooling.
Floor Mounted System (G Models)
PERFORMANCE DATA
The following Performance Data define normal opera&shy;
tion of the system under the above conditions. Relative
humidity does not appear in the tables because after
running the prescribed length of time on recirculated air
and maximum cooling, the relative humidity of the air
passing over the evaporator core will remain at
approximately 35% to 40% regardless of the ambient
temperature or humidity.
Four-Season Air Conditioning (C-K Models)
lbs.-4 oz.)
90&deg; 100&deg; 110&deg; 120&deg;
80&deg;
2000 RPM
150- 160- ISO- 205- 240165 175 195 220 255
888- 11- 1210
10
10
14
15
4144
4245
4548
5053
5558
Overhead System (G Models)
100&deg;
110&deg;
2000
190240
2129
220270
2230
240290
2332
4250
4351
4351
(Refrigerant Charge — 5 lbs.-4 oz.
Temperature of
Air Entering
90&deg; 100&deg; 110&deg; 120&deg;
Condenser
2000
Engine rpm
Compressor
165- 175- 210- 230 265- 305Head Pressure* 180 190 225 245 280 320
Suction
12- 14- 16- 20- 26- 31Pressure*
15
17
19
23
34
29
Discharge Air
Temp, at Right 40- 41- 45- 52- 60- 65Front Upper
43
44 48
55
63
68
Outlet*
o
O
00
90&deg;
o
O
(Refrigerant Charge - 3 Lbs.)
Temperature of
Air Entering
70&deg;
80&deg;
Condenser
Engine rpm
Compressor Head 150- 170Pressure *
205
220
Accumulator
2020Pressure *
26
28
Discharge Air
4141Temp, at Right
47
47
Hand Outlet *
(Refrigerant Charge — 3
Temperature of
Air Entering
70&deg;
Condenser
Engine rpm
Compressor
130Head Pressure* 145
Suction
8Pressure*
10
Discharge Air
Temp, at Right 41Upper Outlet* 44
Overhead System (C-K Models)
(Refrigerant Charge - 5 lbs.-4 oz.)
Temperature of
Air Entering
70&deg;
80&deg; 90&deg; 100&deg; 110&deg;
Condenser
Engine rpm
2000
Compressor
135- 160- 195- 230- 270Head
185 210 245 280 320
Pressure *
Accumulator
2222- 30- 33- 37Pressure *
28
30
38
41
47
Discharge Air
4242- 50- 54- 57Temp, at Right
48
48
58
62
67
Hand Outlet *
Rear Center
4347- 50- 55- 58Outlet *
49
53
58
63
68
Dash Mounted Unit (Motor Home Chassis)
(Refrigerant Charge — 3 lbs.-4 oz.)
Temperature of
Air Entering
Condenser
70&deg;
80&deg;
Engine rpm
90&deg; 100&deg; 110&deg; 120&deg;
2000
Compressor
110- 135- 160- 190- 220- 260Head Pressure* 120 145 170 200 230 270
Suction
Pressure psi*
6
7
9
10
10
13
Discharge Air
Temperature*
4045
4146
4146
4247
4449
4449
* Just prior to compressor clutch disengagement.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
CHECKING OIL
In the six cylinder compressor it is not recommended
that the oil be checked as a matter of course. Generally,
compressor oil level should be checked only where there
is evidence of a major loss of system oil such as might be
caused by:
• A broken refrigerant hose
• A severe hose fitting leak
• A very badly leaking compressor seal
• Collision damage to the system components
As a quick check on compressor oil charge, operate the
engine at idle on maximum cold for approximately 10
minutes, turn off the engine and momentarily crack open
the oil drain plug on bottom of the compressor letting a
slight amount of oil drain out. Retighten plug. Again
slightly crack open the plug. If oil comes out, the
compressor has the required amount of oil.
NOTE: The oil may appear foamy. This is
considered normal.
To further check the compressor oil charge, should the
above test show insufficient oil, it is necessary to remove
the compressor from the vehicle, drain and measure the
oil as outlined under &quot;Checking Compressor Oil
Charge.&quot;
Checking Compressor Oil Charge
1. Run the system for 10 minutes at 500-600 engine
rpm with controls set for maximum cooling and
high blower speed.
2. Turn off engine, discharge the system, remove
compressor from vehicle, place it in a horizontal
position with the drain plug downward. Remove the
drain plug and, tipping the compressor back and
forth and rotating the compressor shaft, drain the
oil into a clean container, measure and discard the
oil.
3. Add new refrigeration oil to the compressor as
follows.
a. If the quantity drained was 4 fluid oz. or more,
add the same amount of new refrigeration oil to
the replacement compressor.
1A-49
b. If the quantity drained was less than 4 fluid oz.,
add 6 fluid oz. of new refrigeration oil to the
replacement compressor.
c. If a new service compressor is being installed,
drain all oil from it and replace only the amount
specified in Steps 3a and 3b above.
d. If a field repaired compressor is being installed,
add an additional 1 fluid oz. to the compressor.
4. In the event that it is not possible to idle the
compressor as outlined in Step 1 to effect oil return
to it, proceed as follows:
a. Remove the compressor, drain, measure and
discard the oil.
b. If the amount drained is more than 1-1/2 fluid
oz. and the system shows no signs of a major
leak, add the same amount to the replacement
compressor.
c. If the amount drained is less than 1-1/2 fluid oz.
and the system appears to have lost an excessive
amount of oil, add 6 fluid oz. of clean
refrigeration oil to replacement compressor, 7
fluid oz. to a repaired compressor.
If the oil contains chips or other foreign
material, replace the receiver-dehydrator (expan&shy;
sion tube on C-K models) and flush or replace all
component parts as necessary. Add the full 11
fluid oz. of new refrigeration oil to the
replacement compressor.
5. Add additional oil in the following amounts for any
system components being replaced.
Evaporator C ore....................................... 3 fluid oz.
Condenser................................................... 1 fluid oz.
Receiver-Dehydrator............................... 1 fluid oz.
Accum ulator............................................... 1 fluid oz.
CAUTIO N: When adding oil to the compressor,
it will be necessary to tilt the rear end of the
compressor up so that the oil will not run out of
the suction and discharge ports. Do not set the
compressor on the shaft end.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-50 HEATER A N D AIR C O N D IT IO N IN G
REFRIGERANT QUICK-CHECK PROCEDURE
The following procedure can be used to quickly determine whether or not an air conditioning system has a proper charge
of refrigerant. This check can be made in a manner of minutes thus facilitating system diagnosis by pinpointing the problem
to the amount of charge in the system or by eliminating this possibility from the overall checkout.
C-K Models
1.
2.
3.
4.
Engine must be warm (thermostat open).
Hood and body doors open.
Selector lever set at A/C.
Temperature lever at first detent to the right of COLD (set
for outside air).
5. Blower on HI.
6. Engine idling at 1000 RPM.
7. Feel temperature of evaporator inlet and accumulator out&shy;
let pipes with compressor engaged (fig. 52).
a. If both are cold this is a proper condition.
b. If inlet pipe is cooler than outlet pipe, system is low on
charge.
• Add a slight amount of refrigerant until both pipes
feel the same (system stabilized —3-5 minutes).
• Then add 15 oz. (1 can) additional refrigerant.
G Models and Motor Home Chassis Units
Start engine and place on fast idle. Set controls for
maximum cold with blower on high.
Bubbles present in sight No bubbles. Sight glass
clear.
&laquo;
glass.
?
System low on charge. System is either fully
Check with leak detector. charged or empty. Feel
Correct leak, if any, and high and low pressure
fill system to proper pipes at compressor. High
pressure pipe should be
charge.
warm; low pressure pipe
should be cold.
r 11— 1 1
No appreciable tempera&shy; Temperature differential
ture differential noted at noted at compressor.
compressor. |
I
System empty or nearly Even though a differential
empty. Turn off engine is noted, there exists a
and connect Charging possibility of overcharge.
Station. Induce 1/2# of An overfilled system will
refrigerant in system (if result in poor cooling dur&shy;
system will not accept ing low speed operation
charge, start engine and (as a result of excessive
draw 1/2# in through low head pressure). An overfill
pressure side). Check is easily checked by dis&shy;
system with leak detector. connecting the compressor
clutch connector while
observing the sight glass.
r 1&quot; &quot;1....
If refrigerant in sight glass If refrigerant foams and
remains clear for more then settles away from
than 45 seconds (before sight glass in less than 45
foaming and then settling seconds, it can be assumed
away from sight glass) an that there is a proper
overcharge is indicated. charge of refrigerant in
Verify with a performance system. Continue checking
check.
out system using perfor&shy;
m ance checks outlined
previously.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
1A-51
Fig. 52-Checking Evaporator Inlet and Accumulator
Outlet Temperatures
M A IN TEN A N C E A N D ADJUSTMENTS
THERMOSTATIC SWITCH
All systems make use of a thermostatic switch with either
an air or fin sensing capillary. This capillary controls the
switch by sensing the temperature of the air leaving the
fins (G and Motor Home Units) or temperature of the
fins (C-K models).
Checking for Proper Operation
G and Motor Home Chassis Units
1. Install the gauge set and set up the vehicle as
described under &quot;Perform ance Test.&quot;
2. Movement of the temperature control knob should
result in a definite change in suction pressure and
cycling of the compressor clutch.
• If compressor continued to operate regardless of
the knob adjustment, it indicates that the switch
points are fused which will lead to evaporator
freeze-up. Replace the switch.
• If the compressor does not operate, regardless of
the position of the knob, a loss of the power
element charge is indicated (provided that it has
been established that power is supplied to the
switch). This, of course, results in no cooling.
Replace the switch.
• Check the switch adjusting screw for stripped or
otherwise damaged threads.
C-K Models
1. Install the gauge set and set up the vehicle as
described under &quot;Perform ance Test&quot;.
2. Set the control at A/C, HI blower, max COLD and
run the engine at 2000 rpm.
• The therm ostatic switch should cycle the
compressor off when the low limit of the outlet
air temperature is reached (see Performance
Data). If it does not, the switch points are fused
which will lead to evaporator freeze up. Replace
the switch.
• If the compressor does not operate, a loss of
power element charge is indicated (provided that
it has been established that power is supplied to
the switch). This, of course, results in no cooling.
Replace the switch.
• Check the switch adjusting screw for stripped or
otherwise damaged threads.
Adjusting Switch
If, after the above checks, the switch seems to be
operating properly, adjust for proper setting if necessary,
as follows:
1. Vehicle must be set up as described in &quot;Perform &shy;
ance Test.&quot;
2. The suction side of the system, read on the low
pressure gauge, should pull down to the pressure
shown in the chart in &quot;Perform ance D ata&quot; under
the ambient temperature at the time the switch is
being set.
3. Remove the switch as outlined in the &quot;Component
Part Replacement&quot; section of this manual.
4. Remove the switch non-metal end plate to gain
access to the switch adjusting screw.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-52 HEATER A N D AIR C O N D IT IO N IN G
5. If the outlet temperature was less than the
prescribed temperature at the end of each cooling
cycle, turn the adjusting screw a partial turn
counterclockwise (fig. 53). If the outlet temperature
was more than prescribed temperature, turn the
adjusting screw clockwise.
NOTE: One turn of the adjusting screw will
change the outlet temperature approximately
4 degrees.
6. Reinstall switch end plate and reinstall switch.
Reinstall face plate (Motor Home Chassis Units) or
evaporator cover (G models) before attempting a
performance test. Be sure that the air sensing
capillary has been replaced properly.
7. Check system performance. If further adjustment is
needed, repeat Steps 3 through 6 until the
prescribed pressure is reached.
NOTE: Do not attempt to run a Performance
Check with the system disassembled since
inaccurate readings would be the result.
ALWAYS reinstall switch and capillary and
any duct work before running a performance
check.
EXPANSION VALVE (Fig. 54)
An expansion valve is used on C-K Model Overhead
Systems, all G Model systems and Motor Home Chassis
Units.
A malfunction of the expansion valve will be caused by
one of the following conditions; valve stuck open, valve
stuck closed, broken power element, a restricted screen or
an improperly located or installed power element bulb.
Attachment of the expansion valve bulb to the
evaporator outlet pipe is very critical. The bulb must be
attached tightly to the pipe and must make good contact
with the pipe along the entire length of the bulb. A loose
THERMOSTATIC
SWITCH
Fig. 54-Expansion Valve
bulb will result in high &quot;high side&quot; pressures and poor
cooling. On bulbs located outside the evaporator case,
insulation must be properly installed.
Indications of expansion valve trouble provided by the
Performance Test are as follows:
VALVE STUCK OPEN
Noisy Compressor.
No Cooling - Freeze Up.
VALVE STUCK CLOSED, PLUGGED SCREEN
OR BROKEN POWER ELEM ENT
Very Low Suction Pressure.
No Cooling.
POORLY LOCATED POWER ELEMENT BULB
Normal Pressure.
Poor Cooling.
Check for Defective Valve
FOAM
INSULATION
SWITCH TOCOVER SCREWS
COVER
Fig. 53-Thermostatic Switch Adjustment
The following procedure must be followed to determine
if a malfunction is due to a defective expansion valve.
1. Check to determine if the system will meet the
performance test as outlined previously. If the
expansion valve is defective, the low pressure
readings will be above specification.
2. The loss of system performance is not as evident
when the high side pressure is below 200 PSI.
Therefore, it may be necessary to increase the
system high side pressure by partially blocking the
condenser. Disconnect the blower lead wire and
repeat the &quot;Performance Check&quot; to determine if
the low side pressure can be obtained.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
3. The system will also indicate a low refrigerant
charge by bubbles occurring in the sight glass.
ENGINE IDLE COMPENSATOR
This additional aid to prevent stalling during prolonged
hot weather periods is included with all air conditioned
1A-53
vehicles. The idle compensator is a thermostatically
controlled air bleed which supplies additional air to the
idle mixture. On V-8 engines, with factory installed air
conditioning systems, the compensator is located within
the carburetor and is accessible when the engine air
cleaner is remove.
GENERAL REPAIR PROCEDURES
PREPARING SYSTEM FOR REPLACEMENT
OF COMPONENT PARTS
Air conditioning, like many other things, is fairly simple
to service once it is understood. However, there are
certain procedures, practices and precautions that should
be followed. For this reason it is strongly recommended
that the preceding information in this section be studied
thoroughly before attempting to service the system.
G reat emphasis must be placed upon keeping the system
clean. Use plugs or caps to close system components and
hoses when they are opened to the atmosphere. Keep
your work area clean.
In removing and replacing any part which requires
unsealing the refrigerant circuit the following operations,
which are described in this section, must be performed
in the sequence shown.
1. Purge the system by releasing the refrigerant to the
atmosphere.
2. Remove and replace the defective part.
3. Evacuate, charge and check the system.
W ARNING: Always wear protective goggles
when working on refrigeration systems.
Goggles J-5453 are included in the set of air
conditioning special tools. Also, beware of the
danger of carbon monoxide fumes by
avoiding running the engine in closed or
improperly ventilated garages.
FOREIGN MATERIAL IN THE SYSTEM
Whenever foreign material is found in the system, it
must be removed before restoring the system to
operation.
In the case of compressor mechanical failure, perform
the following operations:
1. Remove the compressor.
2. Remove the receiver-dehydrator or expansion tube
and discard the unit.
3. Flush the condenser to remove foreign material
which has been pumped into it.
4. Disconnect the line at the evaporator core inlet (CK Four-Season System) or inlet line to the
expansion valve (except C-K Four-Season System).
Inspect the expansion tube or inlet screen of the
expansion valve for the presence of metal chips or
other foreign material. If the tube or screen is
plugged, replace it. Reconnect the line to the
evaporator core or expansion valve.
5. Install the replacement compressor.
6. Add the necessary quantity of oil to the system (one
fluid ounce because of receiver-dehydrator replace&shy;
ment plus the quantity needed for the replacement
compressor - see &quot;Checking Compressor Oil
Charge&quot; under &quot;Checking Oil.&quot;
7. Evacuate, charge and check system.
REFRIGERANT LINE CONNECTIONS
&quot; 0 &quot; Rings
Always replace the &quot;O &quot; ring when a connection has been
broken. When replacing the &quot;O &quot; ring, first dip it in clean
refrigeration oil. Always use a backing wrench on &quot;O &quot;
ring fittings to prevent the pipe from twisting and
damaging the &quot;O &quot; ring. Do not overtighten. Correct
torque specifications are as follows:
CAUTION: Where steel to aluminum connec&shy;
tions are being made, use torque for aluminum
tubing.
Metal
Thread and
Tube
Fitting
O.D.
Size
7/16
1/4
3/8
5/8
3/4
1/2
5/8
7/8
3/4
1-1/16
* Foot Pounds
Steel
Tubing
Torque*
13
33
33
33
33
Alum.
Tubing
Torque*
6
12
n
20
25
Hose Clamps
When hose clamp connections are encountered, special
procedures are necessary for both removal and
installation.
Removal
1. Carefully, with a sharp knife, make an angle cut in
LIGHT DUTY TRUCK SERVICE MANUAL
1A-54 HEATER A N D AIR C O N D IT IO N IN G
the hose as shown in Figure 55. This should loosen
the hose so that it may be worked off the fitting.
2. Cut off slit end of hose.
CAUTIO N : Use only approved refrigeration
hose. Never use heater hose. Use extreme care
not to nick or score the sealing beads when
cutting off the hose. Cutting the hose lengthwise
may result in this problem.
Installation
1. Coat tube and hose with clean refrigeration oil.
2. Carefully insert hose over the three beads on the
fitting and down as far as the fourth, or locating
bead. Hose must butt against this fourth bead.
CAUTIO N: Use no sealer o f any kind.
3. Install clamps on hose, hooking the locating arms
over the cut end of the hose.
4. Tighten the hose clamp screw to 35-42 in. lbs.
torque. DO NOT RETORQUE. The clamp screw
torque will normally decrease as the hose conforms
to the force of the clamp. The screw should be
retorqued only if its torque falls below 10 in. lbs. In
this case, retorque to 20-25 in. lbs. Further
tightening may damage the hose.
REPAIR OF REFRIGERANT LEAKS
Any refrigerant leaks found in the system should be
repaired in the m anner given below:
Leaks at &quot; 0 &quot; Ring Connection
1. Check the torque on the fitting and, if too loose,
tighten to the proper torque. Always use a backing
wrench to prevent twisting and damage to the &quot;O &quot;
ring. Do not overtighten. Again leak test the joint.
2. If the leak is still present, discharge the refrigerant
from the system as described under &quot;Evacuating
and Charging Procedures.&quot;
3. Inspect the &quot;O &quot; ring and the fitting and replace if
damaged in any way. Coat the new &quot;O &quot; ring with
clean refrigeration oil and install carefully.
4. Retorque the fitting, using a backing wrench.
5. Evacuate, charge and check the system.
Leaks at Hose Clamp Connection
1. Check the tightness of the clamp itself and tighten
if necessary. Recheck for leak.
2. If leak has not been corrected, discharge the system
and loosen clamp and remove hose from connec&shy;
tion. Inspect condition of hose and connector.
Replace scored or damaged parts.
3. Dip end of new hose in clean refrigeration oil and
carefully reinstall over connector. Never push end
of hose beyond the locating bead. Properly torque
the clamp.
4. Evacuate, charge and check the system.
Compressor Leaks
MAKE ANGULAR CUT
FOR HOSE REMOVAL
If leaks are located around the compressor shaft seal or
shell, replacement of necessary seals should be made as
outlined under “Compressor” in the Overhaul Manual.
NOTE: A slight amount of oil leakage past
the compressor front seal is considered
normal.
HOSE CLAMP
LOCATING
BEAD
HOSE CLAMP
HOSE
HOSE
SEALING
BEADS
Fig. 55 -Hose Clamp Connections
LOCATING
BEAD
REFRIGERANT HOSE FAILURE
After a leak or rupture has occurred in a refrigerant
hose, or if a fitting has loosened and caused a
considerable loss of refrigerant and oil, the entire system
should be flushed and recharged after repairs have been
made. If the system has been open to atmosphere for
any prolonged period of time the receiver-dehydrator or
accumulator should be replaced.
Because of the length of the hoses on these systems, hose
leaks may be repaired using the following procedure:
1. Locate the leak. This may require removing the
body inner side panels to gain access to the hoses
(Overhead Systems).
2. Discharge the system.
3. Cut out the leaking portion of the hose, making
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
sure that all of the failed portion is removed. If
only a very small portion of the hose was removed,
it may be possible to splice the two ends together
using a special hose connector and two hose clamps.
If several inches of hose must be removed, a new
piece of hose should be spliced in using two
connectors and four hose clamps. Dip the ends of
the hoses in clean refrigeration oil before installing
the hoses onto the connector. Never push the end of
the hose beyond the locating bead of the connector.
Torque the clamp to 35-42 in. lbs.
NOTE: Be sure to replace the hose in the
body in the same m anner as when removed.
If the hose protective grommets are badly
mutilated, they should be replaced.
4. Evacuate, charge and check the system.
COMPRESSOR
C-K Models
Removal (Fig. 56)
1. Purge the refrigerant from the system.
2. Remove connector attaching bolt and connector.
Seal connector outlets.
3. Disconnect electrical lead to clutch actuating coil.
4. Loosen brace and pivot bolts and detach belt.
5. Remove the nuts and bolts attaching the compres&shy;
sor brackets to the mounting bracket.
6. Before beginning any compressor disassembly,
drain and measure oil in the compressor. Check for
evidence of contamination to determine if rem ain&shy;
der of system requires servicing. Compressor
servicing information is located in the Overhaul Manual.
Installation
1. If oil previously drained from the compressor upon
removal shows no evidence of contamination,
replace a like amount of fresh refrigeration oil into
the compressor before reinstallation. If it was
necessary to service the entire system because of
excessive contamination in the oil removed, install a
full charge of fresh refrigeration oil into the
compressor.
2. Position compressor on the mounting bracket and
install all nuts, bolts and lock washers.
3. Install the connector assembly to the compressor
rear head, using new &quot;O &quot; rings coated with clean
refrigeration oil.
4. Connect the electrical lead to the coil and install
and adjust compressor belt.
5. Evacuate, charge and check the system.
1A-55
G and Motor Home Chassis Models
Removal (Fig. 56)
1.
2.
3.
4.
Disconnect battery ground cable.
Disconnect compressor clutch connector.
Purge the system of refrigerant.
Release the belt tension at the idler pulley and
remove the belt from the compressor pulley. On
some vehicles it may be necessary to remove the
crankshaft pulley in order to remove the belt.
5. G Models-Remove the front air conditioning
distributor duct described later in this section.
6. G Models-Remove the two bolts and two clamps
that hold the engine cover and remove the cover.
7. Remove the air cleaner to aid access to the
compressor.
8. Remove fitting and muffler assembly and cap or
plug all open connections.
9. Remove the nuts and bolts attaching the compres&shy;
sor to the bracket.
10. Remove the engine oil tube support bracket bolt
and nut from the compressor, also compressor
clutch ground lead.
11. Remove bolt and nut holding muffler assembly to
front of compressor (also holds vacuum line on
power assisted brake equipped vehicles; if neces&shy;
sary, remove vacuum hose at manifold end).
Before beginning any compressor disassembly, drain and
measure oil in the compressor. Check for evidence of
contamination to determine if rem ainder of system
requires servicing. Compressor Servicing inform ation is
located in the Overhaul Manual.
Installation
1. If the oil drained from the compressor showed no
evidence of contamination, replace a like amount of
fresh refrigeration oil into the compressor before
reinstallation. If it was necessary to service the
entire system because of excessive contamination in
the oil removed, install a full charge of fresh
refrigeration oil in the compressor. (See Checking
Compressor Oil Charge in the Service Manual.)
2. Position compressor on the mounting bracket and
install all nuts, bolts, lock washers, and mount oil
dip stick tube, muffler, vacuum brake hose (if
equipped), and ground wire.
3. Install the connector assembly to the compressor
rear head, using new &quot;O &quot; rings coated with clean
refrigeration oil.
4. Connect the electrical lead to the coil and install
and adjust compressor belt, using idler pulley. See
&quot;Compressor Belt Tension Adjustment.&quot;
5. Evacuate, charge and check the system.
6. Replace air cleaner. On G models, replace the
engine cover and air distributor duct.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-56 HEATER A N D AIR C O N D IT IO N IN G
307- 350 V- 8
G
C-K
MODELS AND MOTOR HOME CHASSIS
4 5 4 V -8 C-K MODELS
Fig. 56-Compressor Mountings
Compressor Belt Tension Adjustment
Adjust the compressor belt to the specifications shown in
the Tune-Up chart in the Engine section of the Service
Manual.
NOTE: On some G and Motor Home Chassis
models it may be necessary to increase idler
pulley slack adjustm ent. This may be
accomplished by (1) Remove and discard the
idler adjustment bolt. (2) Remove the idler
backing plate and elongate all 3 adjusting
slots 1/2 inch inboard or outboard as
required. (3) Reinstall the idler assembly and
adjust belt tension using a lever (screwdriver,
etc.) to move the pulley outboard until proper
belt tension is reached. If the belt is being
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER AND AIR C O N D IT IO N IN G
replaced it may be necessary to remove and
replace the throttle cable during the belt
replacement. If so check throttle cable
adjustment upon completion. It may also be
necessary to remove the crankshaft pulley to
install a new compressor belt.
COMPRESSOR FAILURE
If the compressor has failed mechanically to the extent
that metal chips and shavings are found in it, the system
should be checked for foreign material and cleaned as
described under Foreign M aterial in the System.
FALSE COMPRESSOR SEIZURE
Slipping or broken air conditioning drive belts and/or
scored clutch surfaces may be experienced on initial start
up of an air conditioning compressor after an extended
period of storage or non-operation of the compressor.
This would indicate a seized compressor; however, an
overhaul or replacement of the compressor may not be
necessary.
During extended periods of non-operation, changes in
temperature cause the refrigerant in the air conditioning
compressor to expand and contract. During this
movement, lubricating oil carried by the refrigerant
tends to migrate from highly polished surfaces in the
compressor such as the ball seats and wobble plate.
W ithout lubricating oil at these polished surfaces, they
&quot;w ring&quot; together and appear to be seized.
Before the time and expense of an overhaul is invested,
use the following check to determine if the compressor is
actually seized. With a wrench on the compressor shaft
lock nut or Spanner Wrench J-9403 on ihe clutch drive
plate, &quot;rock&quot; the shaft in the opposite direction of
normal rotation. After the compressor is broken loose,
&quot;rock&quot; the shaft back and forth. This should be sufficient
to return lubricating oil to the &quot;wrung&quot; surfaces and
allow the compressor shaft to be turned by hand. Once
the compressor turns freely, rotate the compressor at
least three complete turns. Start the engine and operate
the compressor for a minimum of one minute.
This procedure will not affect a compressor that is
actually seized but should be attem pted before
overhauling a compressor known to be idle for a month
or longer.
COLLISION PROCEDURE-ALL SYSTEMS
Whenever a vehicle equipped with an air conditioning
unit is involved in a collision or wreck, it should be
inspected as soon as possible. The extent of damage to
any or all of the component parts and the length of time
the system has been exposed to the atmosphere will
determine the replacement of parts and processing that
will be required. The greater the length of time of
exposure to the atmosphere, the greater will have been
the chances for air, moisture and dirt to have entered
and damaged the system. Every case may be entirely
1A-57
different so it is not possible to establish a hard and fast
procedure to follow each time. Good judgment must be
used to determine what steps should be taken in each
specific case.
The following procedure is presented as a guide for use
when inspecting a damaged vehicle equipped with air
conditioning.
1. Remove the drive belt.
2. Visually inspect the condenser, accumulator,
receiver-dehydrator, compressor, mounting brack&shy;
ets, conditioning unit, all connecting lines, and all
controls to determine the extent and nature of the
damage.
a. No repairs, such as soldering, welding or
brazing, should be attempted on the condenser
because of its construction. If the vapor passages
in the horizontal tubes or return bends or
manifolds have been damaged in any way, the
condenser should be replaced with a new one.
b. The accumulator or receiver-dehydrator should
be replaced if there is any evidence of its
having sustained either internal damage or a
fracture at any of the lines or welded joints or if
the system has been exposed to the atmosphere
for an undetermined period of time.
c. Examine the compressor for any visible external
damage.
d. The evaporator should be examined for damage
and, if necessary, removed or replaced or the
entire unit processed where damaged or exposed
to the atmosphere.
e. All connecting lines and flexible hoses should be
examined throughout their entire length for
damage. If damaged in any manner, replace
with new lines.
f. Check all controls and connecting wires for
damage and replace with new parts where
needed.
g. Check the clutch pulley for proper operation
and freedom from damage.
3. Install Charging Station.
4. Purge the system.
5. Remove the compressor from mounting and
remove the oil test fitting.
6. Pour out the oil into a clean glass container and
examine it for any foreign substance such as dirt,
water, metal particles, etc. If any of these are
present, the compressor, expansion tube, and
accumulator or receiver-dehydrator should be
replaced and the other system components should
be flushed with liquid refrigerant.
7. If the oil is clean and free of any harmful
substance, replace oil with Frigidaire 525 Viscosity
Oil, or equivalent.
NOTE: If the system components have been
LIGHT DUTY TRUCK SERVICE MANUAL
1A-58 HEATER A N D AIR C O N D IT IO N IN G
replaced or flushed, replace the full charge of
oil. If not, add no more fresh oil than was
drained in Step 6.
8. Charge up the compressor to cylinder or can
pressure and leak test the compressor seals prior to
installation of compressor.
9. Reinstall the compressor and evacuate the system
by following the Evacuating Procedure.
10. Introduce R-12 vapor at cylinder (room) tempera&shy;
ture and pressure.
11. Leak test all fittings and connections and give
particular attention to a leak test at the compressor
shaft seal if compressor has not been leak tested on
the bench.
12. Complete system processing and charge system.
C O M P O N E N T PART REPLACEMENT
FOUR-SEASON SYSTEM-C-K MODELS
CONDENSER (Fig. 57)
Replacement
1.
2.
3.
4.
5.
6.
7.
8.
9.
Disconnect battery ground cable.
Purge the system of refrigerant.
Remove the grille assembly.
Remove the radiator grille center support.
Remove the left grille support to upper fender
support (2) screws.
Disconnect the condenser inlet and outlet lines and
the outlet tube line at the right end of the
condenser. Cap or plug all open connections at
once.
Remove the condenser to radiator support screws.
Bend the left grille support outboard to gain
clearance for condenser removal.
Remove the condenser assembly by pulling it
forward and then lowering it from the vehicle.
Fig. 5 7 -Condenser Installation (C-K Models)
10. To install a new condenser, reverse Steps 1-9 above.
Add one fluid ounce of clean refrigeration oil to a
new condenser.
NOTE: Use new &quot;O &quot; rings, coated with clean
refrigeration oil, when connecting all refrig&shy;
erant lines.
11. Evacuate, charge and check the system.
ACCUMULATOR
Replacement (Fig. 58)
1. Disconnect the battery ground cable and the
compressor clutch connector.
2. Purge the system of refrigerant.
WARNING: Be sure system is completely
purged of refrigerant before completely
disconnecting refrigerant lines.
Fig. 58--Accumulator Installation (C-K Models)
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
3. Disconnect the accumulator inlet and outlet lines
and cap or plug the open connections at once.
4. Remove the outlet line clamp screw and the
accumulator clamp screw and remove the unit from
the vehicle.
5. If a new accumulator is being installed, add 1 fluid
ounce of clean refrigeration oil to the new
accumulator.
6. Install the new unit following Steps 1-4 in reverse
order. Connect all lines using new &quot;O &quot; rings, coated
with clean refrigeration oil.
CAUTION: Do not uncap the new unit until
ready to fasten the inlet and outlet line to the
unit.
7. Evacuate charge and check the system.
BLOWER ASSEMBLY
Replacement
1. Disconnect the battery ground cable.
2. Disconnect the blower motor lead and ground
wires.
3. Disconnect the blower motor cooling tube.
4. Remove the blower to case attaching screws and
remove the blower assembly. Pry the blower flange
away from the case carefully if the sealer acts as an
adhesive.
5. Remove the nut attaching the blower wheel to the
motor shaft and separate the assemblies.
6. To install, reverse Steps 1-5 above; replace sealer as
necessary.
EVAPORATOR CORE
Replacement (Fig. 59)
1. Disconnect the battery ground cable.
1A-59
2. Purge the system of refrigerant.
3. Remove the nuts from the selector duct studs
projecting through the dash panel.
4. Remove the cover to dash and cover to case screws
and remove the evaporator case cover.
5. Disconnect the evaporator core inlet and outlet
lines and cap or plug all open connections at once.
6. Remove the thermostatic switch and the expansion
tube assemblies.
7. Remove the evaporator core assembly.
8. To install, reverse Steps 1-7 above. Add three
ounces of clean refrigeration oil to a new
evaporator core.
CAUTION: Be sure to install the thermostatic
switch capillary in the hole provided in the new
core.
NOTE: Use new &quot;O &quot; rings, coated with clean
refrigeration oil, when connecting refrigerant
lines.
Be sure cover to case and dash panel sealer is
intact before reinstalling cover.
9. Evacuate, charge and check the system.
EXPANSION TUBE
The expansion tube is located in the evaporator core
inlet line.
Replacement (Fig. 60)
1. Purge the system of refrigerant.
2. Disconnect the condenser to evaporator line at the
evaporator inlet. Cap the open line at once.
Fig. 60 -Expansion Tube (C-K Four-Season System)
LIGHT DUTY TRUCK SERVICE MANUAL
1A-60 HEATER A N D AIR C O N D IT IO N IN G
3. Using needle-nose pliers, remove the expansion
tube from the evaporator core inlet line (fig. 60).
4. Remove the expansion tube &quot;O &quot; ring from the core
inlet line.
5. To install, reverse Steps l-4 above.
NOTE: Install the expansion tube using a
new &quot;O &quot; ring, coated with clean refrigeration
oil.
6. Evacuate, charge and check the system.
SELECTOR DUCT AND HEATER CORE
ASSEMBLY
Replacement (Figs. 61 and 62)
1. Disconnect the battery ground cable.
2. Drain the radiator and remove the heater hoses
from the core tubes. Plug the core tubes to prevent
coolant spillage during removal.
3. Remove the glove box and door as an assembly.
4. Remove the center duct to selector duct and
instrument panel screws and remove the center
lower and center upper ducts.
5. Disconnect the bowden cable at the temperature
door.
6. Remove the nuts from the three selector duct studs
projecting through the dash panel.
7. Remove the selector duct to dash panel screw
(inside vehicle).
8. Pull the selector duct assembly rearward until the
core tubes clear the dash panel. Lower the selector
assembly for enough to gain access to all vacuum
and electrical harness.
9. Disconnect the vacuum and electrical harness and
remove the selector duct assembly.
10. Remove the core mounting strap screws and remove
the core.
11. To install, reverse Steps 1-10 above.
12. Refill coolant system and connect the battery
ground strap.
KICK PAD VALVE
Replacement (Fig. 63)
1.
2.
3.
4.
Disconnect the vacuum hose at the actuator.
Unhook the valve return spring at the actuator end.
Remove the actuator bracket mounting screws.
Remove the cam to actuator arm screw and
separate the actuator and bracket from the cam.
5. Remove the actuator to bracket nuts and separate
the actuator and bracket.
6. To install reverse Steps 1-5 above.
PLENUM VALVE
Replacement (Fig. 63)
1. Raise the hood.
2. Remove the cowl plastic grille.
3. Remove the three cowl to valve assembly screws
and remove the valve assembly from the vehicle.
4. Remove the actuator arm push nut.
5. Remove the actuator to valve nuts and separate the
valve and actuator.
6. To install, reverse Steps 1-5 above.
CONTROL ASSEMBLY
Removal (Fig. 64)
1. Disconnect the battery ground cable.
2. Remove the radio as outlined in Section 15 of this
manual.
3. Remove the instrument panel bezel.
4. Remove the control to instrum ent panel screws and
lower the control far enough to gain access to the
control assembly.
CAUTIO N: Be careful not to kink the bowden
cable.
Disconnect the bowden cable, vacuum harness and
electrical harness at the control.
Remove the control through the radio opening.
If a new unit is being installed, transfer all
electrical switches and vacuum valves to the new
control.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-61
Fig. 62 -Air Selector and Ducts (C-K Models)
8. To reinstall, reverse Steps 1-6 above. Check control
operation.
MASTER SWITCH AND/OR BLOWER
SWITCH
The master switch is located on top of the control
assembly.
Replacement
1. Disconnect the battery ground cable.
2. Remove the instrument panel bezel.
3. Remove the control to instrument panel screws and
allow control to rest on top of the radio.
4. Remove the switch to control screws, disconnect the
electrical harness at the switch and remove the
switch assembly.
5. To install a new switch, reverse Steps 1-4 above.
VACUUM TANK
The vacuum tank is mounted to the engine side of the
dash panel above the blower assembly (fig. 65).
Replacement
1. Disconnect the vacuum lines at the tank.
2. Remove the tank to dash panel screws and remove
the tank.
3. To install, reverse Steps 1 and 2 above.
BLOWER MOTOR RESISTOR
The blower motor resistor is located in the blower side of
the blower-evaporator case (fig. 66).
Replacement
1. Disconnect the wiring harness at the resistor.
2. Remove the resistor to case attaching screws and
remove the resistor.
3. Place the new resistor in position and install the
attaching screws.
4. Connect the resistor wiring harness.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-62 HEATER A N D AIR C O N D IT IO N IN G
BLOWER MOTOR RELAY
The blower motor relay is located on the blower side of
the blower-evaporator case (fig. 66).
Replacement
1. Disconnect the wiring harness at the relay.
2. Remove the relay to case attaching screws and
remove the relay.
3. Place the new relay in position and drive the
mounting screws.
4. Connect the relay wiring harness.
THERMOSTATIC SWITCH
The thermostatic switch is mounted to the blower side of
the blower-evaporator case. The switch sensing capillary
extends into the evaporator core.
Replacement
1. Disconnect the battery ground strap.
2. Disconnect the wiring harness at the switch.
3. Remove the switch to case screws and remove the
switch carefully so as not to damage the capillary
tube.
NOTE: Note capillary tube position in the
core so that the capillary may be reinstalled
in the same position (fig. 67).
4. Place the new switch in position, installing the
capillary in the core in the same m anner as at
switch removal.
5. Drive the switch mounting screws, connect the
wiring harness and the battery ground strap.
DISCHARGE PRESSURE SWITCH
The discharge pressure switch is located in the condenser
to evaporator line (fig. 68).
Replacement
1.
2.
3.
4.
Disconnect the battery ground cable.
Purge the system of refrigerant.
Disconnect the wiring harness at the switch.
Remove the switch from the refrigerant line.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER AND AIR C O N D IT IO N IN G
1A-63
BLOWER RESISTOR
THERMOSTATIC
SWITCH ASSEMBLY
EVAPORATOR
CORE
i
BLOWER RELAY
CAPILLARY
POSITION IN
CORE
THERMOSTATIC SWITCH
Fig. 67-Replacing Thermostatic Switch
Fig. 66-Resistor, Relay and Thermostatic Switch (C-K
Models)
5. To replace, reverse Steps 1-4 above.
NOTE: Be sure to use new &quot;O &quot; rings, coated
with clean refrigeration oil, when installing
the switch.
6. Evacuate charge and check system operation.
FUSE
A 25 amp fuse, located in the junction block protects the
entire air conditioning system except for the blower
when operating at HI.
A second 25 amp fuse, to protect the HI speed blower
circuit, is located in the electrical wiring between the
junction block and the blower relay (fig. 69).
LIGHT DUTY TRUCK SERVICE MANUAL
1A -64 HEATER A N D AIR C O N D IT IO N IN G
C O M P O N E N T PART REPLACEMENT
OVERHEAD SYSTEM-C-K MODELS
The Overhead System is used in conjunction with the
Four-Season System. Since replacement of Four-Season
System components has been covered previously, only
those components peculiar to the Overhead System will
be covered in this section.
REAR DUCT
This duct covers the blower-evaporator assembly, at the
rear of the vehicle, and incorporates four adjustable air
outlets (fig. 70).
Replacement
1. Disconnect the battery ground cable.
2. Disconnect the drain tube from the rear duct.
3. Remove the screws securing the duct to the roof
panel.
4. Remove the duct from the side and rear retaining
flanges and remove the duct.
5. To install, reverse Steps 1-4 above.
BLOWER MOTOR RESISTOR
The blower motor resistor is located on the cover side of
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-65
Fig. 71-Overhead System Front Wiring (C-K Models)
the Four-Season System blower-evaporator as shown in
Figure 71.
Replacement
1. Disconnect battery ground cable.
2. Disconnect the electrical harness at the resistor.
3. Remove the resistor attaching screws and remove
the resistor.
4. To install a new resistor, reverse Steps 1-3 above.
BLOWER MOTOR ASSEMBLY
Removal
1.
2.
3.
4.
5.
Disconnect the battery ground cable.
Remove the rear duct as outlined previously.
Disconnect the blower motor ground strap.
Disconnect the blower motor lead wire.
Remove the lower to upper blower-evaporator case
screws and lower the lower case and motor
assembly.
CAUTION: Before removing the case screws,
support the lower case to prevent damage to the
case or motor assemblies.
6. Remove the motor retaining strap and remove the
motor and wheels. Remove the wheels from the
motor shaft.
Installation
1. Place the blower wheels onto the motor shaft and
install the setscrews; do not tighten the setscrews at
this time.
CAUTION: Be sure that the blower wheels are
installed as shown in Figure 73.
2. Install the blower motor retaining strap and foam.
3. Place the blower motor and wheel assembly into the
lower case. Align the blower wheels so that they do
LIGHT DUTY TRUCK SERVICE MANUAL
1A-66 HEATER A N D AIR C O N D IT IO N IN G
EVAPORATOR
SCREEN
EXPANSION
VALVE
Fig.
Fig. 73 -Blower Motor (C-K Overhead System)
4.
5.
6.
7.
not contact the case and then tighten the wheel
setscrews.
Place the lower case and blower motor assembly in
position in the vehicle and install the lower to upper
case screws.
NOTE: Rotate the blower wheels to make
sure that they do not rub on the case.
Install the center ground wire and connect the
blower lead wire.
Install the rear duct assembly as described
previously.
Connect the battery ground cable.
EXPANSION VALVE
This system incorporates an expansion valve which does
not utilize an external equalizer line (fig. 74).
2.
3.
4.
5.
6.
Disconnect the battery ground cable.
Purge the system of refrigerant.
Remove the rear duct as outlined previously.
Disconnect the blower motor lead and ground
wires.
5. Remove the lower to upper blower-evaporator case
screws and lower the lower case and motor
assembly.
CAUTION: Before removing the case screws,
support the lower case and motor assemblies.
6. Remove the expansion valve sensing bulb clamps.
7. Disconnect the valve inlet and outlet lines and
remove the expansion valve assembly. Cap or plug
the open connections at once.
Installation
1. Remove caps or plugs from system connections and
EVAPORATOR
CORE
7 4 -E x p a n s io n
V alve
(C-K
SENSING BULB
O v e rh e a d S y s te m )
install the new valve assembly using new &quot;O &quot; rings
coated with clean refrigeration oil.
Install the sensing bulb, making sure that the bulb
makes good contact with the core outlet line.
Install the lower case and blower motor assemblies.
Connect the blower motor lead and ground wires.
Install the rear duct as outlined previously.
Connect the battery ground cable.
Evacuate, charge and check the system.
EVAPORATOR CORE (Fig. 74)
Removal
1.
2.
3.
4.
5.
Removal
1.
2.
3.
4.
BLOWER-EVAPORATOR
UPPER CASE
6.
7.
8.
9.
Disconnect the battery ground cable.
Purge the system or refrigerant.
Remove the rear duct as outlined previously.
Disconnect the blower motor lead and ground wire
connections.
Disconnect the refrigerant lines at the rear of the
blower-evaporator assembly. Cap or plug the open
connections at once.
Remove the blower-evaporator to roof panel
support nuts and washers, lower the blowerevaporator assembly and place it on a work bench
upside down.
Remove the lower to upper case screws and remove
the lower case assembly. Remove the upper case
from the evaporator core.
Remove the expansion valve inlet and outlet lines
and cap or plug the open connections at once.
Remove the expansion valve capillary bulb from
the evaporator outlet line and remove the valve.
Remove the plastic pins holding the screen to the
core and remove the screen.
Installation
1. Install the wire screen to the front of the core and
insert the plastic pins.
2. Install the expansion valve inlet and outlet lines
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
1A-67
5. Install the blower-evaporator to the roof panel
support.
6. Connect the refrigerant lines to the blowerevaporator unit using new &quot;O &quot; rings coated with
clean refrigeration oil.
7. Connect the blower lead and ground wires.
8. Install the rear duct as outlined previously.
9. Connect the battery ground cable.
10. Evacuate, charge and check the system.
BLOWER MOTOR SWITCH
The three-speed (LO-MED-HI) blower motor switch is
located in the instrument panel, just to the left of the ash
tray (fig. 75).
Replacement
Fig. 75-Blower Switch (C-K Overhead System)
using new &quot;O &quot; rings coated with clean refrigeration
oil. Install the sensing bulb to the evaporator outlet
line as shown in Figure 74; make sure the bulb has
good contact with the line.
NOTE: Add 3 oz. clean refrigeration oil
when installing a new core.
3. Install the upper case to the core.
4. Install the lower core case and blower assembly.
1. Disconnect the battery ground cable.
2. Remove the switch retaining screws.
3. Disconnect the wiring harness at the switch and
remove the switch.
4. To install, reverse Steps 1-3 above.
FUSE
The Four Season portion of this system is protected by a
25 amp fuse in the junction block.
The rear blower high speed circuit is protected by a 25
amp in-line fuse, located between the junction block and
the rear blower motor switch.
C O M P O N E N T PART REPLACEMENT
FLOOR M O UNTED SYSTEM -G MODELS
CONDENSER
Replacement (Fig. 76)
1. Remove the battery ground cable and compressor
clutch connector.
2. Purge the system of refrigerant.
3. Remove the screws that retain the headlight
mouldings and remove the screws for the grille.
Remove the mouldings then remove the grille.
4. Remove the screws from radiator center brace and
remove the brace.
5. Disconnect the condenser inlet and outlet lines and
cap or plug the open connections at once.
6. Disconnect the receiver-dehydrator outlet line and
cap or plug the open connections at once.
7. Remove the (4) condenser bracket bolts and remove
the condenser from the vehicle.
8. Remove the condenser mounting brackets from the
condenser.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-68 HEATER AND AIR C O N D IT IO N IN G
9. To install, reverse Steps l-8 above. Add l fluid
ounce of clean refrigeration oil to a new condenser.
CAU TIO N : Use new &quot;O&quot; rings, coated with
clean refrigeration oil, when connecting all
refrigerant lines.
10. Evacuate, charge and check the system.
2. Lift upward and rearward on the top of the
distributor duct assembly and move it away from
the evaporator and blower motor assembly cover,
being careful not to damage the seal.
3. To reinstall, reverse Steps 1 and 2, making sure seal
to evaporator and blower motor cover is properly
positioned.
RECEIVER-DEHYDRATOR
BLOWER-EVAPORATOR COVER
Replacement (Fig. 76)
Replacement (Fig. 78)
1. Disconnect the battery ground cable, and the
compressor clutch connector.
2. Purge the system of refrigerant.
3. Remove the screws that retain the headlight
mouldings and the screws for the grille. Remove the
mouldings and remove the grille.
4. Disconnect the receiver-dehydrator inlet and outlet
lines and cap or plug the connections at once.
5. Remove the receiver-dehydrator bracket attaching
screws.
6. Remove the receiver-dehydrator from the vehicle.
7. If a new receiver-dehydrator is being installed, add
1 fluid ounce of clean refrigeration oil to the new
unit.
8. Connect the inlet and outlet lines using new &quot;O &quot;
rings coated with clean refrigeration oil.
CAU TIO N : Do not uncap the new unit until
ready to fasten the inlet and outlet lines to the
unit.
9. Install receiver-dehydrator by reversing Steps 1-6
above.
10. Evacuate, charge and check the system.
SIGHT GLASS REPLACEMENT
If damage to the sight glass should occur, a new sight
glass kit should be installed. The kit contains the sight
glass, seal and retainer. (See Figure 77).
1. Purge system.
2. Remove the sight glass retainer nut using a
screwdriver and remove old glass and &quot;O &quot; ring
seal.
3. Install the new glass and seal and retainer nut,
being careful not to turn the nut past the face of
the housing. To do so may damage the &quot;O &quot; ring
seal.
4. Evacuate, charge and check the system.
AIR DISTRIBUTOR DUCT ASSEMBLY
Replacement (Fig. 78)
1. Remove four screws that hold the duct to the engine
cover.
1. Remove four screws holding the cover to the
evaporator assembly.
2. Remove the temperature control knob and place the
blower switch on M.
3. Remove the cover being careful not to damage the
seal to the air distributor duct.
4. To reinstall, reverse Steps 1-3, being sure seal to air
distributor duct is properly positioned.
BLOWER-EVAPORATOR ASSEMBLY
Removal (Fig. 79)
1. Disconnect battery ground cable, and compressor
clutch lead from connector.
2. Purge system of refrigerant.
3. Remove the blower-evaporator cover as described
previously.
4. Disconnect inlet and outlet refrigerant lines from
underneath the unit, and cap or plug the
connections at once.
5. Disconnect drain tubes from evaporator case.
6. Remove blower-evaporator assembly bracket bolts.
7. Remove electrical connections from switches,
resistors, relays and blower motor.
8. To install reverse Steps 1-7 above. Make all
refrigerant line connections using new &quot;O &quot; rings,
coated with clean refrigeration oil.
9. Evacuate, charge and check the system.
EXPANSION VALVE and/or EVAPORATOR
CORE
Replacement
1. Remove the blow er-evaporator as described
previously.
2. Remove the cover plate and separate upper and
lower case halves.
3. Disconnect inlet and outlet lines from the
expansion valve. Cap or plug all open connections
at once. Remove sensing bulb from the evaporator
outlet manifold. Remove expansion valve.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A ND AIR C O N D IT IO N IN G
1A-69
Fig. 77-Sight Glass Replacement
EVAPORATOR
CONTROL.
, BLOWER
MOTOR
Fig. 78-Air Distributor Duct and Blower-Evaporator
Cover (Floor Mounted G Models)
4. Remove evaporator core retaining screws and
remove core.
5. Remove blower motor and harness assembly from
case.
6. To install, reverse Steps 1-5 above.
NOTE: Add 3 fluid ounces of new refrigera&shy;
Fig. 79-Blower-Evaporator (G Floor Mounted System)
tion oil to a new core. Use new &quot;O &quot; rings,
coated with clean refrigeration oil, when
connecting all lines.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-70 HEATER A N D AIR C O N D IT IO N IN G
7. Evacuate, charge and check the system.
Replacement
BLOWER MOTOR
Removal
1. Disconnect the battery ground cable and compres&shy;
sor clutch connector.
2. Remove the Front Blower-Evaporator Cover as
previously described.
3. Disconnect the blower motor feed wire and ground
wires.
4. Remove the blower-evaporator cover brackets from
the assembly.
5. Remove the top half of the blower-evaporator case.
6. Remove blower motor mounting strap.
7. Remove blower assembly. Loosen the blower wheel
setscrews and remove the wheels from the motor
shaft.
Installation
1. Install the blower wheels on the motor so that the
lower blades curve toward the dash panel side of
the unit when the motor is placed in the case. Do
not tighten setscrews at this point.
2. Place the motor in the bracket with the electrical
connector side of the motor to the right side of the
bracket. Attach the mounting strap. Aligh blower
wheels so that they do not contact case. Tighten
setscrews.
3. Reverse removal Steps 1-5 for proper installation.
1. Disconnect the battery ground cable and compres&shy;
sor clutch connector.
2. Remove the blower-evaporator cover as described
previously.
3. Disconnect the electrical harness at the switch.
4. Remove the attaching screws and remove the
switch.
5. To install, reverse Steps 1-4 above. Check system
operation.
LOW REFRIGERANT CHARGE PROTECTION
SYSTEM
The low refrigerant charge protector system consists of a
superheat shutoff switch located in the rear head of the
compressor, connected in series by an electrical lead to a
thermal fuse.
During normal air conditioning system operating conditions,
current flows through the air conditioner thermostatic control
switch, and through the thermal fuse link to the clutch coil to
actuate the compressor clutch. Should a partial or total loss of
refrigerant in the system cause the superheat switch to sense
low system pressure and a high suction gas temperature, the
superheat switch contacts will close. When the contacts close,
current flows to energize the resistance type heater in the
thermal fuse, Figure 81. The resultant heat warms the fuse link
to its specific melt temperature, thus opening the circuit to the
compressor clutch coil. Compressor operation ceases and com-
ELECTRICAL COMPONENTS
The front and rear blower switches, thermostatic switch,
front and rear resistors, blower and tie relays are
attached to the blower-evaporator assembly (fig. 80).
BLOWER SWITCHFLOOR SYSTEM
THERMOSTATIC
BLOWER RELAYFLOOR SYSTEM
RESISTOROVERHEAD
SYSTEM
Sw i t c h -
™
J fRLATv0 '
SYSTEM
SYSTEM
Fig. 80- Electrical Components (G Floor Mounted
System)
Fig. 81-Superheat Switch Electrical Schematic
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-71
pressor damage due to a loss of refrigerant charge is prevented.
The cause of the refrigerant loss must be corrected and the
system charged prior to replacing the thermal fuse. The super&shy;
heat switch does not have to be replaced when it cycles and is
reusable unless it is determined that the switch is faulty.
Superheat Switch (Fig. 82)
The switch diaphragm and sensing tube assembly is
charged with R -114 refrigerant and the sensing tube
protrudes into the suction cavity of the rear compressor
head to sense suction gas temperatures. The internal
pressure of the diaphragm and sensing tube assembly is
affected thermally by the suction gas temperature and
the diaphragm affected externally by the suction
pressure.
The electrical contact welded to the diaphragm will only
contact the terminal pin during a low pressure-high
temperature condition. High pressure-high temperature
or low pressure-low temperature conditions will not cause
the contacts to close. The contacts may be either &quot;open&quot;
or &quot;closed&quot; in a Tolerance Zone depending on the
characteristics of the switch and accuracy of pressure and
temperature readings taken.
Fig. 83--Superheat Switch Removal
Replacement
1. Completely discharge the air conditioning system.
2. After the system is discharged, remove the
superheat switch retainer ring, using J-5403 Internal
Snap Ring Pliers (fig. 83).
3. Remove superheat switch from the rear head by
4.
5.
6.
TERMINAL
ELECTRICAL
CONTACT
H O U S IN G
7.
8.
D IAP H R AG M
M TG . BASE
BASE
O P E N IN G S (4)
D IA P H R A G M
ASSEMBLY
S E N S IN G
TUBE
9.
10.
pulling at the terminal housing groove with J-9393
or a pair of screwdrivers.
Remove &quot;O &quot; ring from the switch cavity in the rear
head. Use &quot;O &quot; ring removal Tool J-9553.
Recheck superheat switch for closed contacts. See
Superheat Switch Check in Service Diagnosis Table.
Replace as necessary.
Check the superheat switch cavity and &quot;O &quot; ring
groove in the rear head for dirt or foreign material
and be sure area is clean before installing the &quot;O &quot;
ring. Install a new &quot;O &quot; ring in the groove of the
superheat switch cavity in the rear head. Lubricate
the &quot;O &quot; ring liberally with new refrigeration oil
before installing.
Lubricate housing of the superheat switch with new
refrigeration oil, and insert switch carefully into
switch cavity until switch bottoms. J-9393 may also
be used to install the switch.
Using J-5403 Internal Snap Ring Pliers, install
superheat switch retaining ring with high point of
the curved sides adjacent to the switch housing. Be
sure retainer ring is properly seated in the snap
ring groove.
Check for electrical continuity between the switch
terminal and switch housing to be sure the contacts
are open according to the Calibration Chart (fig.
84).
Evacuate, charge and check system operation.
Thermal Fuse (Fig. 85)
Fig. 82-Superheat Switch Schematic
The thermal fuse consists of a temperature sensitive fuse
LIGHT DUTY TRUCK SERVICE MANUAL
1A-72 HEATER A ND AIR C O N D IT IO N IN G
TOLERANCE ZONE
Fig. 85--Thermal Fuse
SU CTIO N PRESSURE (PSIG)
N O TE:
For gauges c a lib ra te d in inches Hg vacuum , d ivid e
ga u g e re a d in g by 2 .3 0 6 to o b ta in PSIG.
Fig. 84-Superheat Switch Calibration Chart
link, a wire wound resistor and three spade type
electrical terminals, potted with epoxy in a plastic
housing. The terminals are positioned for in-line plug-on
connection with a wiring harness. The thermal fuse
construction provides for a time delay in blowing the
fuse link which prevents &quot;blown fuse&quot; nuisance due to
m om entary switch contact closings during certain
transient conditions.
A blown thermal fuse indicates that the air conditioning
system is either low or completely out of refrigerant
charge, a m alfunctioning expansion valve or an
improperly located thermal limiter.
CIRCUIT BREAKER
The entire air conditioning system is protected by a 45
amp circuit breaker located on the left side of the dash,
in the engine compartment.
C O M P O N E N T PART REPLACEMENT
OVERHEAD SYSTEM -G MODELS
This system is used in conjunction with the floor
mounted system. Since replacement of the floor Mounted
System Components has been covered previously, only
those components peculiar to the Overhead system will
be covered in this section.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
1A-73
BLOWER-EVAPORATOR SHROUD
This shroud covers the blower-evaporator at the rear of
the vehicle, and incorporates four adjustable air outlets.
CORRECT
BLADE
Replacement (Fig. 87)
1. Disconnect the battery ground cable.
2. Disconnect the drain tubes at the rear corners of
the shroud.
3. Remove the screws securing the shroud to the unit
and roof panel.
4. Remove the shroud from the side and rear
retaining flanges and remove the shroud.
5. To install, reverse Steps 1-4 above.
BLOWER MOTOR ASSEMBLIES
Removal (Fig. 88)
1. Disconnect the battery ground cable and compres&shy;
sor clutch connector.
2. Remove the rear shroud as outlined previously.
3. Remove the blower motor ground straps at the
center connector between the motors.
4. Disconnect the blower motor lead wires.
W ARNING: Before removing the case screws,
support the lower case to prevent damage to
the case or motor assemblies.
5. Remove the lower to upper blower-evaporator case
screws and lower the lower case and motor
assemblies.
6. Remove the motor retaining strap and remove the
LOWER
CASE HALF
Fig. 88- Blower Motors (G Overhead System)
motor and wheels. Remove the wheels from the
motor shaft.
Installation
1. Place the blower wheels onto the motor shaft and
install the setscrews; do not tighten the setscrews at
this time.
CAUTIO N: Be sure that the blower wheels are
installed as shown in Figure 88.
2. Install the blower motor retaining strap and foam
strip.
3. Place the two blower motor and wheel assemblies
into the lower case. Align the blower wheels so that
they do not contact the case and then tighten the
wheel setscrews.
4. Place the lower case and blower motor assemblies
in position in the vehicle and install the lower to
upper case screws.
NOTE: Rotate the blower wheels to make
sure that they do not rub on the case.
5. Install the center ground wires and connect the
blower lead wires.
6. Install the rear shroud assembly as described
previously.
7. Connect the battery ground cable and compressor
clutch connector.
EXPANSION VALVES
This system incorporates two expansion valves. These
valves do not use an external equalizer line (fig. 89).
Removal (Inner Valve)
Fig. 87-Blower-Evaporator Shroud (G Overhead
System)
1. Disconnect the battery ground cable and compres&shy;
sor clutch connector.
2. Purge the system of refrigerant.
3. Remove the rear shroud as outlined previously.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-74 HEATER A N D AIR C O N D IT IO N IN G
VALVE SENSING
BULBS
6. Remove the blower-evaporator to roof panel
attachm ents and lower the blower-evaporator
assembly. Remove the assembly and place on a
work bench upside down.
7. Remove the lower to upper case screws and remove
the lower case assembly. Remove the upper shroud
from the upper case and then remove the upper
case from the core.
8. Remove the expansion valve bulb from the
evaporator outlet line. Remove the expansion valve
inlet and outlet lines and cap or plug the open
connections at once. Remove the valve.
Installation (Outer Valve)
VALVES
Fig. 89--Expansion Valves (G Overhead System)
W ARNING: Before removing the lower case
screws, support the case to prevent damage to
the case or motor assemblies.
4. Disconnect the center ground wire and the blower
motor lead wires. Remove the lower to upper case
screws and lower the lower case and blower motor
assemblies.
5. Disconnect the valve sensing bulb from the core
outlet line.
6. Disconnect the core inlet and outlet lines and
remove the valve assembly. Cap or plug the open
connections at once.
installation (Inner Valve)
1. Remove caps or plugs from system connections and
install the new valve assembly using new &quot;O &quot; rings
coated with clean refrigeration oil.
2. Install the sensing bulb, making sure that the bulb
makes good contact with the core outlet line.
3. Install the lower case and blower motor assemblies.
4. Install the rear shroud as outlined previously.
5. Connect the battery ground cable and compressor
clutch connector.
6. Evacuate, charge and check the system.
1. Remove the caps or plugs from the refrigerant
connections and install the new valve using new
&quot;O &quot; rings coated with clean refrigeration oil. Install
the sensing bulb, making sure that the bulb makes
good contact with the core outlet line.
2. Install the upper case to the core making sure the
sealing strips are positioned correctly. Install the
upper shroud on the upper case.
3. Install the lower case and blower assemblies.
4. Install the blower-evaporator to the roof panel.
5. Connect the refrigerant lines at the rear of the
blower-evaporator unit using new &quot;O &quot; rings coated
with clean refrigeration oil.
6. Connect the blower lead wires and ground straps.
7. Install the rear shroud as described previously.
8. Connect the battery ground cable and the
compressor clutch connector.
9. Evacuate, charge and check the system.
BOW
SUPPORT
Removal (Outer Valve)
1. Disconnect the battery ground cable and compres&shy;
sor clutch connector.
2. Purge the system of refrigerant.
3. Remove the rear shroud as outlined previously.
4. Disconnect the blower motor ground straps and
leads.
5. Disconnect the refrigerant lines at the rear of the
blower-evaporator assembly. Cap or plug all open
connections at once.
EVAP &amp;
BLOWER ASM
SUPPORT
BLOWER M O TO R
GRD WIRES
BRACKET
Fig. 90-Blower-Evaporator (G Overhead System)
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
EVAPORATOR CORE (Fig. 90)
1. Disconnect the battery ground cable and compres&shy;
sor clutch connector.
2. Purge the system of refrigerant.
3. Remove the rear shroud as outlined previously.
4. Disconnect the blower motor leads and ground
wire.
5. Disconnect the refrigerant lines at the rear of the
blower-evaporator assembly. Cap or plug open
connections at once.
WARNING: Before removing the blowerevaporator unit, support the case to prevent
damage to components.
6. Remove the blower-evaporator to roof panel
attachm ents and lower the blower-evaporator
assembly. Remove the assembly and place it on a
work bench upside down.
7. Remove the lower to upper case screws and remove
the lower case assembly. Remove the upper shroud
and upper case from the evaporator core.
8. Remove the expansion valve inlet and outlet lines
and cap or plug the open connections at once.
Remove the expansion valve capillary bulbs from
the evaporator outlet line and remove the valves.
9. Remove the plastic pins holding the screen to the
core and remove the screen.
1A-75
7. Connect the blower lead wires and ground straps.
Install the rear shroud as outlined previously.
9. Connect the battery ground cable and the
compressor clutch connector.
10 . Evacuate, charge and check the system.
RESISTOR
See Electrical Components in the Floor Mounted System
Section of this manaul (fig. 80).
BLOWER SWITCH
See Blower Switch in the Floor Mounted System Section
of this manual (fig. 80).
REAR BLOWER RELAY
The rear blower relay is attached to the instrument panel
reinforcement, just left of the steering column (fig. 91).
Replacement
1. Disconnect battery ground cable.
Disconnect relay wiring harness at the relay.
3. Remove the relay attaching screw and remove the
relay.
4. To install, reverse Steps 1-3 above. Check system
operation.
2.
TIE RELAY
See Electrical Components in the Floor Mounted System
Section of this manual (fig. 80).
Installation
1. Install the wire screen to the front of the new core
and insert the plastic pins.
2. Install the expansion valve inlet and outlet lines
using new &quot;O &quot; rings coated with clean refrigeration
oil. Install the sensing bulbs to the evaporator outlet
line. Make sure the bulbs have good contact with
the line.
NOTE: Add 3 oz. clean refrigeration oil
when installing a new core.
3. Install the upper case and upper shroud to the core.
4. Install the lower core case and blower assemblies.
5. Install the blower-evaporator to the roof panel.
6. Connect the refrigerant lines to the blowerevaporator unit using new &quot;O &quot; rings coated with
clean refrigeration oil.
C O M P O N E N T PART REPLACEMENT
DASH M O U N TED SYSTE M -M O TO R HO M E CHASSIS
This system is installed on the vehicle and checked at
CONDENSER
assembly. The blower-evaporator is then disconnected
Replacement
and shipped with the chassis unit to the body supplier.
For this reason, it will only be possible to give basic
replacement procedures on some components.
1. Disconnect the battery ground cable.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-76 HEATER A N D AIR C O N D IT IO N IN G
Fig. 92--Condenser (Motor Home Chassis Unit)
2. Purge the system of refrigerant.
3. Disconnect the condenser inlet and outlet lines and
cap or plug all open connections at once.
4. Remove the condenser to radiator support screws
and remove the condenser.
5. To install a new condenser, reverse Steps l -4 above.
Add one fluid ounce of clean refrigeration oil to a
new condenser.
NOTE: Use new &quot;O &quot; rings, coated with clean
refrigeration oil, when connecting all refrig&shy;
erant lines.
6. Evacuate, charge and check the system.
Fig. 93--Receiver-Dehydrator (Motor Home Chassis
Unit)
6. Evacuate, charge and check the system.
SIGHT GLASS REPLACEMENT
Refer to &quot;Sight Glass Replacement&quot; in the Floor
Mounted System Section of this manual.
BLOWER-EVAPORATOR ASSEMBLY (Fig. 94)
Removal
1. Disconnect battery ground cable.
RECEIVER-DEHYDRATOR
Replacement (Fig. 93)
1. Disconnect the battery ground cable.
2. Purge the system of refrigerant.
3. Disconnect the inlet and outlet lines at the receiverdehydrator and cap or plug the open lines at once.
4. Remove the receiver-dehydrator bracket attaching
screws and remove the bracket and receiverdehydrator.
5. To install a new receiver-dehydrator, reverse Steps
1-4 above. Add one fluid ounce of clean
refrigeration oil to a new receiver-dehydrator.
NOTE: Use new &quot;O &quot; rings, coated with clean
refrigeration oil, when connecting all refrig&shy;
erant lines.
Units)
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
2. Purge system of refrigerant.
3. Disconnect inlet and outlet refrigerant lines from
the back of unit. Cap or plug all open connections
at once.
4. Disconnect drain tubes from evaporator case.
5. Disconnect electrical connector from compressor.
Remove the terminal (See Figure 95) and allow
connector to hang on ground wire.
6. Remove screws securing grommet retainer to dash
panel. Remove wire from grommet through slit.
7. Disconnect electrical lead at connector.
8. Remove unit mounting bolts. Remove unit from
vehicle, carefully pulling compressor electrical lead
through dash panel.
Once the unit has been removed from the vehicle,
continue with component replacement as follows:
BLOWER ASSEMBLY
Removal (Fig. 96)
1. Remove the cover plate and separate the upper and
lower case halves. Remove blower motor mounting
strap screw and remove strap.
2. Remove blower assembly. Loosen the blower wheel
setscrews and remove the wheels from the motor
shaft.
Installation
1. Install the blower wheels on the motor so that the
lower blades curve toward the dash panel side of
the unit when the motor is placed in the case as
illustrated in Figure 96. Do not tighten setscrews at
this point.
2. Place the motor in the bracket with the electrical
connector side of the motor to the right side of the
bracket. Attach the mounting strap. Align blower
1A-77
CORRECT
BLOWER
BLADE
ANGLE
Fig. 96--B!ower Assembly (Motor Home Chassis Unit)
wheels so that they do not contact case. Tighten
setscrews.
3. Assemble the case halves and attach the cover plate.
4. Reverse steps 1-8 on the &quot;Blower-Evaporator
Assembly&quot; removal procedure.
5. Evacuate, charge and check the system.
EXPANSION VALVE, EVAPORATOR AND/OR
EVAPORATOR CASE
Removal (Fig. 97)
1. Remove the cover plate and separate upper and
lower case halves.
2. Remove inlet and outlet lines from the expansion
valve. Remove sensing bulb from the evaporator
outlet manifold. Remove expansion valve. Cap or
plug open connections at once.
TERMINAL
SCREW DRIVER
(NARROW BLADE)
THERMOSTATIC SWITCH
CAPILLARY TUBE
SCREEN
MESH
CONNECTOR
TANG
GROOVE
A. Insert screw driver in groove &amp; press
tang toward terminal to release.
BUMPER
EXPANSION VALVE
B. Pry tang back out to insure locking
when reinstalled into connector._____
Fig. 95-Terminal Removal
Fig. 97-Expansion Valve (Motor Home Chassis Unit)
LIGHT DUTY TRUCK SERVICE MANUAL
1A-78 HEATER A ND AIR C O N D IT IO N IN G
AIR SENSING CAPILLARY
SWITCH
2. Reverse steps 1-8 of the &quot;Blower Evaporator
Assembly&quot; removal procedure.
3. Evacuate, charge and check the system.
THERMOSTATIC AND/OR BLOWER
SWITCHES
Replacement
BUMPER
BLOWER SWITCH
Fig. 98- Thermostatic and Blower Switches
3. Remove evaporator core retaining screws and
remove core.
4. Remove blower motor and harness assembly from
case.
Installation
1. Reverse applicable steps in the removal procedure.
CAUTIO N: Use new &quot;O&quot; rings coated with
clean refrigeration oil when connecting lines.
Add 3 oz. of new refrigeration oil to a new
core.
1. Remove the cover plate assembly from the
evaporator case.
2. Remove two screws securing either switch to the
cover plate and remove appropriate switch (fig. 98).
3. Install replacement switch, reinstall cover plate and
reverse steps 1-8 of the &quot;Blower-Evaporator
Assembly&quot; removal procedure.
NOTE: When installing thermostatic switch,
be sure to position sensing capillary as when
unit was removed.
RESISTOR
The blower motor resistor is located on the top of the
unit. The entire unit must be removed to replace the
resistor.
FUSE
This Unit does not incorporate an in-line fuse. The lead
wire is connected to the Heater W iring Harness and
operates off the 20 amp Heater Fuse.
D IA G N O S IS
REFRIGERANT SYSTEM
The following is a description of the type of symptom
each refrigerant component will evidence if a defect
occurs:
Compressor
A compressor defect will appear in one of four ways:
Noise, seizure, leakage, or low discharge pressure (fig.
99).
NOTE: Resonant compressor noises are not
cause for alarm; however, irregular noise or
rattles may indicate broken parts or excessive
clearances due to wear. To check seizure, de&shy;
energize the magnetic clutch and check to see
if drive plate can be rotated. If rotation is
impossible, compressor is seized (See &quot;False
Compressor Seizure&quot;). To check for a leak,
refer to leak testing in the service manual.
Low discharge pressure may be due to a
faulty internal seal of the compressor, or a
restriction in the compressor.
Low discharge pressure may also be due to
an insufficient refrigerant charge or a
restriction elsewhere in the system. These
possibilities should be checked prior to
servicing the compressor. If the compressor is
inoperative, but is not seized, check to see if
current is being supplied to the magnetic
clutch coil terminals.
Condenser
A condenser may be defective in two ways: it may leak,
or it may be restricted. A condenser restriction will result
in excessive compressor discharge pressure. If a partial
restriction is present, sometimes ice or frost will form
immediately after the restriction as the refrigerant
expands after passing through the restriction. If air flow
through the condenser or radiator is blocked, high
discharge pressures will result. During normal condenser
operation, the outlet pipe will be slightly cooler than the
inlet pipe.
Receiver-Dehydrator
A defective receiver-dehydrator may be due to a
restriction inside the body of the unit. A restriction at
the inlet to the receiver-dehydrator will cause high head
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER A N D AIR C O N D IT IO N IN G
pressures. Outlet tube restrictions will be indicated by
low head pressures and little or no cooling. An
excessively cold receiver-dehydrator outlet may be
indicative of a restriction.
Expansion Valve
A malfunction of the expansion valve will be caused by
one of the following conditions: valve stuck open, valve
stuck closed, broken power element, a restricted screen or
an improperly located or installed power element bulb.
The first three conditions require valve replacement. The
last two may be corrected by replacing the valve inlet
screen and by properly installing the power element
bulb.
Attachment of the expansion valve bulb to the
evaporator outlet line is very critical. The bulb must be
attached tightly to the line and must make good contact
with the line along the entire length of the bulb. A loose
bulb will result in high low side pressures and poor
cooling.
Indications of expansion valve trouble are provided by
Performance Tests; consult Diagnostic Charts.
VALVE STUCK OPEN
Noisy Compressor.
No Cooling - Freeze Up.
VALVE STUCK CLOSED, BROKEN POWER
ELEMENT OR PLUGGED SCREEN
Very Low Suction Pressure.
No Cooling.
POORLY LOCATED POWER ELEMENT BULB
Normal Pressure.
Poor Cooling.
Diagnosis for Defective Valve
The following procedure must be followed to determine
if a malfunction is due to a defective expansion valve.
1. Check to determine if the system will meet the
performance test as outlined previously. If the
expansion valve is defective, the low pressure
readings (evaporator pressure) will be above
specifications.
2. The loss of system performance is not as evident
when the compressor head pressure is below 200
psi. Therefore, it may be necessary to increase the
system head pressure by partially blocking the
1A-79
condenser. Disconnect the blower lead wire and
repeat the &quot;perform ance check&quot; to determine if the
evaporator pressure can be obtained.
3. The system will also indicate a low refrigerant
charge by bubbles occurring in the sight glass.
Evaporator
When the evaporator is defective, the trouble will show
up as an inadequate supply of cool air. A partially
plugged core due to dirt, a cracked case, or a leaking seal
will generally be the cause.
Refrigerant Line Restrictions
Restrictions in the refrigerant lines will be indicated as
follows:
1. Suction Line - A restricted suction line will cause
low suction pressure at the compressor, low
discharge pressure and little or no cooling.
2. Discharge Line - A restriction in the discharge line
generally will cause the pressure relief valve to
open.
3. Liquid Line - A liquid line restriction will be
evidenced by low discharge and suction pressure,
and insufficient cooling.
Sight Glass Diagnosis (G and Motor Home
Chassis Units)
At temperatures higher than 70 degrees F, the sight glass
may indicate whether the refrigerant charge is sufficient.
A shortage of liquid refrigerant is indicated after about
five minutes of compressor operation by the appearance
of slow-moving bubles (vapor) or a broken column of
refrigerant under the glass. Continuous bubbles may
appear in a properly charged system on a cool day. This
is a normal situation. If the sight glass is generally clear
and performance is satisfactory, occasional bubbles do
not indicate refrigerant shortage.
If the sight glass consistently shows foaming or a broken
liquid column, it should be observed after partially
blocking the air to the condenser. If under this condition
the sight glass clears and the performance is otherwise
satisfactory, the charge shall be considered adequate.
In all instances where the indications of refrigerant
shortage continues, additional refrigerant should be
added in 1/4 lb. increments until the sight glass is clear.
An additional charge of 1/2 lb. should be added as a
reserve after the glass clears. In no case should the
system be overcharged.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-80
HEATER
COMPRESSOR DIAGNOSIS
COMPRESSOR NOT EN G A G E D .
Check fo r proper ground and
good clean electrical contact
If coil is s till inoperative,
at term inals.
replace compressor coil.
Check fo r proper air gap.
If previous step does not
C orrect if necessary.
correct clu tch slippage,
(.0 2 2 .0 5 7 )
COMPRESSOR EN G A G E D
C O N D IT IO N IN G
CLUTCH SLIPPIN G .
AIR
PROPER V O LT A G E
TO
COMPRESSOR C O IL.
repair compressor.
BUT NOT O P E R A T IO N A L .
B E L T SLIPPIN G .
Check and correct
belt tension.
R E F R IG E R A T IO N
IS D E P L E T E D .
HIGH TO RQ UE CO M PRESSOR.
(S E IZ E D )
CHARGE
SYS T EM HAS SOME
R E F R IG E R A N T .
L E A K S FR E O N .
COMPRESSOR
THRO W S O IL.
Blow out seal cavity
w ith air hose and
leak test.
L
Add one pound
refrigerant.
Leak test com plete
Repair compressor.
system before
Operate and leak
removing compressor.
test system.
Repair compressor.
DOES NOT
Wipe o ff o il - O.K.
LIGHT
DUTY
TRUCK
SERVICE
MANUAL
Fig. 99-Compressor Diagnosis
AND
Retrace electrical circuit back to source of power loss. (See wiring diagrams).
C-K Models:
Check for defective discharge Pressure Switch by jumping switch connector terminals. If compressor
operates, check for low refrigerant charge. If charge is satisfactory, switch is defective-replace.________
NO V O LT A G E A T
COMPRESSOR CO IL.
i
INSUFFICENT C O O L IN G -F O U R SEASON SY STEM (C-K M ODELS)
M ove temperature lever rapidly back and forth from max
heat to max. cold Listen for temperature door hitting at each end
| Not Hitting I
Hitting
1
2
3.
4.
5
6
Set Temperature Lever at Detent to the Right of Cold
Set Selector Lever at A / C
Set Blower Switch on High
O pen Doors and Hood
W arm Engine
Run Engine at ldle( Except 06 Models)
1000 RPM ( C -K 06 Models)
Adjust Door
Feel For Air Flow A t Heater And A / C Outlets
Some or All A ir Flow From Heater Outlet
Check M ode Door O peration-Repair,
---1-------
O ff All the Time
A ir Flow From
A / C Outlets O nly
Engaged or Cycling
NOTE
Check Compressor Hot Lead W ire W ith Test
I
Check Visually For Compressor Clutch O peration
______________________ ______________________
Light or Place a Jumper W ire From The
Compressor to The Positive ( +) Terminal of
THIS SYSTEM DOES N O T H A V E A SIG H T GLASS. UNDER N O
CIRCUMSTANCES SHOULD A SIGHT GLASS BE INSTALLED
The Battery.
I
I_________________
Feel Liquid Line Before Expansion Tube
| N ot Engaged
W a rm l
Cold
Locate Restriction, Repair, Evacuate
-----------------1------------------
Charge and Check The System
I
( O K .)
Lov
Plugged Expansion Tube.Repair
or Replace and Evacuate, Charge
and Check System.
Below 50 PSIG
| A b o ve 50 PSIG _ ___
Lost Charge Leak Test and
Repair. Evacuate,
D efective Switch
Charge and Check System,
Jump Switch
Cycles on and O ff
O n Continuously
( O K.)
Check For Missing Expansion Tube
LIGHT
|
Compressor Runs
M issing&quot;&quot;}1
l
r
^
DUTY
In Place
Replace
System
System
Install Expansion Tube, Evacuate,
Check Compressor
( O K .)
Charge and Check System.
Inlet Screen
TRUCK
Plugged
i
I
Leak Check System,
Replace Switch, Evacuate,
Charge and Check System.
( O K .)
I
System
( O K.)
Defective Thermostatic Switch
I
System
Clean
( O K .)
i
System
( O K .)
CONDITIONING
Defective Thermostatic
Switch
I
I
Replace
System
( O K .)
r
(O K .)Check Compressor Cycling
I
System
Replace
I
I
Frost
I
I
at High Side Fitting
( At Pressure Switch)
System
r
D efective
Switch
AIR
System
System
( O K .)
and Evacuate, Charge and
Check System
Thermostatic
Switch
AND
I
(OK.)
N o Frost
Pipes Same Temperature ( Cold)
or O utlet C older Than Inlet
Replace Expansion Tube
High To Normal
and O bserve Accumulator and
Evaporator Pipes For Frost.
( OK.)
Discharge
Pressure Switch
Check Refrigerant Pressure
Check Accumulator Pressure
( See Performance Data)
Change Blower Speed To Low,
System
1
Pipes Still Cold and
W arm as A bove
Outlet Temperature High See Performance Data
j
I
Check For O p e n Circuit
at the Follow ing t
HEATER
Outlet Temperature Satisfactory or
too cold - See Performance Data
O veraul Manual
T
Leak Check System-Repair Leak If No
Leak is Found, Check Expansion Tube
For Plugged Filter Evacuate and Charge
System. Check Inlet &amp; O utlet Pipe Temperatures.
Install the Thermometer in A / C O utlet and
Check Performance-See Performance Test
and Performance Data O utlined Earler in
This Section
I
System
A p p ly External G round to Compressor,
if Clutch is Still not Engaged , Replace
Compresor Clutch - See the
IL
Inlet Pipe Colder
Than Outlet Pipe
Pipes same Temperature or
Outlet Colder Than Inlet
Engaged
Check For Blown M ain Fuse
Feel Evaporator Inlet and Accumulator Outlet Pipes
Restriction in High Side of System.
Visually Look For Frost Spot to
|
T
i
System O ver-C harged.P urge,
i
Evacuate, Charge and Check System,
M ANUAL
System
System
( O.K.)
( O K .)
Fig. 100--lnsufficient Cooling Diagnosis-C-K Four-Season System
1A-81
SERVICE
Repair or Replace Screen, E vacuate,
Charge and Check System,
1A-82
INSUFFICIENT COOLING DIA GNO SIS CHART (EXCEPT C -K FOUR-SEASON SYSTEM)
NO RM AL A IR FLOW
IN O OR LOW A IR FLOW
CHECK BLOWER OPERATIO N
)_ t NO R M A L
I
CHECK SIGHT GLASS
ICE BLO C KIN G
EVAP O R ATO R
|-
NO FO AM ING
SYSTEM IS PR O B A B LY LOW ON R E FR IG E R A N T.
CHECK FOR LEAK S, REPA IR , AN D ADD
R E F R IG E R A N T. IF FO AM IN G S T IL L OCCURS,
CHECK FOR RESTR IC TIO N IN R E FR IG E R A N T
SYSTEM BETW EEN CONDENSER A N D SIGHT
GLASS.
CHECK FOR LOW EVAP O R ATO R PRESSURE
1. A LLO W SYSTEM TO W ARM UP.
2. STOP A N D R ESTART ENGINE.
3. CHECK EVAP O R ATO R PRESSURE
IM M E D IA T E L Y A FTE R RESTART AN D
PULL DOWN OF EVAP O R ATO R PRESSURE.
1. SYSTEM MAY BE EITH E R F U L L Y CHARG ED OR EM PTY.
FEEL HIGH AND LOW PRESSURE PIPES A T COMPRESSOR.
HIGH PRESSURE PIPE SHO U LD BE W ARM . LOW PRESSURE
PIPES SHOULD BE COLD.
2. IF PIPES ARE NOT IN D IC A T IN G PROPER TEM PERATURES,
RECHARGE SYSTEM AS RECO M M ENDED. IF N O ZZLE A IR
TEMPERATURE IS S T IL L HIG H . CHECK EVAP O RATO R
PRESSURE.
N O R M A L EVAPO RATO R
PRESSURE
LOW EVAP O R ATO R
*
PRESSURE
X
LOW EVAP O RATO R
‘ PRESSURE
'C H E C K EVAPORATOR PRESSURE
I
Check fo r m alfunctioning
expansion valve-See
Component Diagnosis.
HIGH EVAP O RATO R
*
PRESSURE
CHECK EVAP O R ATO R O U TLE T LINE
EVAP O RATO R O U TLET
L IN E W ARM
SYSTEM HAS EXCESS M O ISTURE. REPLACE RECEIVER
D E H Y D R A TO R A N D E V AC U ATE TH O R O U G H LY . RECHARGE
SYSTEM.
I
CHECK COMPRESSOR DISCH ARG E PRESSURE
NORM AL
EVAP O RATO R PRESSURE
| Check Compressor Discharge Pressure.
1. CHECK FOR L IQ U ID LIN E RESTRICTION
(FROST SPOT ON LIN E ). IF NOT,
2. CHECK FOR PLUGGED IN L E T SCREEN IN
EXPANSION V A L V E . IF NOT,
3. CHECK FOR D E FE C TIVE EXPANSION V A L V E
BY R EM O V IN G V A L V E AN D BLOW ING THRO UGH
V A L V E . IF U N A B LE TO BLO W THRO UGH V A LV E ,
BULB IS D ISC H ARG ED. REPLACE EXPANSION
VALV E.
LOW DISCHARGE
*
PRESSURE
I
LIGHT
Check fo r m alfunctioning
expansion valve-See
Component Diagnosis.
HIG H DISCH ARGE PRESSURE
LOW DISCHARGE PRESSURE
X
1. Check engine cooling system, fan clutch and check
fo r restricted air flo w thru condenser.
2. Check expansion valve bulb contact. Correct if
necessary.
3. Check fo r refrigerant restriction in condenser.
Return bends at equal elevation should be
approxim ately same temperature. If temperature
of bends is appreciably diffe re n t, the cooler
bend indicates a restricted circuit, replace con&shy;
denser if restriction is found, If condenser is OK,
check fo r air in system. To check observe outle t
air tem perature and compressor discharge
pressure w hile slowly discharging system at
receiver inlet connection.
Check for restriction in liquid line,
p artia lly plugged inlet screen at
expansion valve, or defective
expansion valve, replace valve if
defective.
X
N O R M AL DISCH ARGE PRESSURE
R efrigeration System is ok
1. Check fo r proper fu n c tio n of heater TEM P ER ATU R E door.
2. Check fo r proper sealing of evaporator case.
3. Check fo r proper operation and seal around tem perature door.
4. Non-Foam ing sight glass does not always indicate a fu lly
charged system. Add 1/2 lb. refrigerant and observe
performance.
5. Check fo r excess oil in system. A sym ptom of excess o il is a
slipping clutch or belt or broken belt. To remove excess oil
in system consult service manual.
DUTY
TRUCK
’ REFER TO PERFORM ANCE
C H A R T FOR CORRECT PRESSURES
SERVICE
M ANUAL
Fig. 101-Insufficient Cooling Diagnosis-Except C-K Four-Season System
C O N D IT IO N IN G
Check fo r loose or disconnected air distrib u tio n ducts,
restricted or leaking air ducts, partially closed air o u t&shy;
let valve or clogged evaporator core, if above check is
OK, check for ice blocking evaporator.
AIR
CHECK FOR BLOWN FUSE, D E FE C TIVE BLOW ER SWITCH,
BROKEN W IRE, LOOSE CONNECTIONS. LOOSE BLOWER MOTOR
GROUND W IRE OR IN O P E R A T IV E BLOWER MOTOR.
BLOWER O PE R ATIO N |
AND
a m in g
fo r condenser air blockage due to foreign material.
fo r proper air ducting hose connections.
heater temperature door adjustm ent, adjust if incorrect.
evaporator sealing fo r air leak, repair if leaking.
pressure gages and therm om eter and make performance test.
BLOWER NOT OPERATING
HIGH O U TLET AIR
TEMPERATURE
CHECK FOR A IR LEAK S TH RO UG H DASH PANEL.
DOORS, WINDOWS, OR FROM HEATER .
Check
Check
Check
Check
Install
CHECK A IR FLOW
| CHECK DISCH ARGE A IR TEM P ERATURE (SEE PERFORMANCE D A T A ) |
D ISCH ARG E TE M P ER ATU R E
A T O U T L E T COLD
5.
6.
7.
8.
9.
HEATER
The fo llo w in g procedures should be applied before perform ance testing an A/C System.
1. Check fo r proper belt installation and tension w ith J-23600.
2. Check fo r proper clutch coil terminal connector installation.
3. Check fo r clutch air Gap (.022 - .057).
4. Check fo r broken, burst, or cut hoses. Also check fo r loose fittin g s on all components.
ELEC TRIC A L SYSTEM D I A G N O S T IC CHART
BLOW ER M OTOR IN O P E R A T IV E
(C E R T A IN SPEEDS-EXCEPT HIGH
OIM C-K FO U R -S EAS O N )
B LO W E R M O T O R IN O P E R A T IV E
(A N Y S P E E D )
Check fo r proper
fuse
|F U S E
|
BLO W N !
fuse
o k
!
Disconnect resistor connectors, connect one lead
of a self powered test lig h t to any one term inal
and use the other lead to probe each o f the
other term inals.
T h e fo llo w in g tests sh o u ld be m ade
W ith ign. switch in &quot; R u n &quot; position
and heater or A /C on, locate short in
one of the fo llo w in g wires: (see note)
w it h th e ig n itio n s w itc h in ''R u n ''
p o s itio n , h ea ter o r A /C on and
b lo w e r s w itc h on h ig h .
C-K Four-Season System
C heck b lo w e r m o to r g ro u n d
1. From fuse panel to master
switch on control.
2. From master switch to compressor
clutch.
3. Master sw itch to blower switch.
4. From blow er speed switch to
resistor.
5. From resistor to blow er m otor.
|P O O R
OR NO G R 0 U N D |
I Repair g ro u n d |
GROUND
T E S T L IG H T
OK
DOES NO T
T E S T L IG H T
L IG H T O N A L L T E R M IN A L S
.............
C heck m o to r c o n n e c to r w ith
I
1 ..................
R eplace re sisto r
12 v o lt te st lig h t.
W ith ig n itio n switch in &quot; R u n &quot; p osition and heater
or A /C on, use 12 v o lt test lamp to check fo r
voltage at resistor connector w ith b low er speed
switch in each position.
-L
L A M P D O E S N O T L IG H T
| LA M P L IG H T S ]
T
Except C-K Four-Season
C heck w ire c o n n e c to r on
Replace m o to r
1. From fuse panel to blower switch.
2. From blow er switch to resistor.
3. From resistor to blow er m otor.
L A M P L IG H T S
|L A M P L IG H T S !
| L A M P D O E S N O T L IG H t |
IN A L L
R epair o pe n in
m o to r to b lo w e r
re sisto r to b lo w e r re la y ).
re la y w it h 12 v o lt te s t lig h t.
relay.
|
DOES N O T L IG H T ]
I
lam p
l ig h t s
!
la m p
u g h t s
]
Replace b lo w e r re la y.
DUTY
speed s w itc h .
TRUCK
o f f
LA M P DOES N O T L IG H T
ON A L L W IRES
Replace b lo w e r speed
R e p a ir o p e n in
s w itc h .
a ffe c te d w ire .
|
M ANUAL
1A-83
SERVICE
T
b lo w e r re la y.
CONDITIONING
LIGHT
R eplace re sisto r
re sisto r to b lo w e r
la m p
I
R e pa ir o pe n in w ire
fro m re sisto r to
AIR
_L
|
[ L A M P D O E S N O T L IG H T !
AND
L A M P L IG H T S
C heck F E E D w ire fro m
P O S IT IO N S
Turn ig n itio n key o ff and p u t Heater or A /C
C ontrol in o ff position. W ith blow er resistor w ire
connector disconnected, connect a ju m pe r lead
fro m battery positive term inal to the w ire term in al
in connector. Use 12 v o lt test lig h t to check fo r
voltage at w ire at blow er speed switch connector.
Repeat same test on the other wires.
LA M P LIG H TS ON
A L L W IRES
w ire te rm in a ls a t re s is to r.
L A M P O FF
IN A L L
HEATER
w ire fro m b lo w e r
fro m
C heck w ire c o n n e c to r o n b lo w e r
Replace re la y
R eplace b lo w e r
L A M P D O E S N O T L IG H T
C o n n e c t 12 v o lt te s t lig h t a t w ire
Use 12 v o lt test lig h t a nd ch eck
speed s w itc h .
P O S IT IO N S
te rm in a l on b lo w e r re la y (w ire
(L A M P
T
1
b lo w e r re la y w it h 12 v o lt te s t lig h t.
NOTE: S h ort c irc u it may be in te r&shy;
m itte n t. If tester does not indicate
a short c irc u it, move heater harness
around as much as possible to re&shy;
create short c irc u it. W atch and listen
fo r arcing.
IL A M P O N |
L IG H T S ON
A L L T E R M IN A L S
R e pa ir o pen in w ire
fro m b lo w e r speed sw itch .
Fig. 102-Electrical System Diagnosis Chart
1A-84
BLOW ER M O TO R IN O P E R A T IV E
A T H IG H SPEED O N LY
(C-K FO U R -SEASO N SYSTEM )
HEATER
ELECTRICAL SYSTEM D IA G N O S T IC CHART
COM PRESSOR C LU TC H IN O P E R A T IV E 1
... 1
Check fuse
FUSE B LO W N
AND
X
Check
in-line fuse
[ FUSE O K |
FUSE BLO W N
|F U S E O K |
C onnect Tester. Use to check
w ire fro m ju n c tio n to b lo w e r
relay to locate sh o rt. Repair
sh o rt c irc u it as .re q u ire d .*
CL ICK H E A R D
I
I
'
I NO C LIC K H E A R D !
1
_
Check w ire te rm in a l on relay
th a t goes to ju n c tio n blo ck
w ith 12 v o lt test lam p.
Check relay c o il c o n n e cto r
w ith 12 v o lt te s t lig h t.
X
LA M P L IG H T S
Replace b lo w e r
relay.
|L A M P DOES N O T L IG H T |
___ _
1
Repair open in w ire
fro m ju n c tio n b lo c k
to relay.
j LA M P
1
LIG H T S |
1
Check ground
on relay
| lA M P DOES N O T L IG H T |
f—*
Check w ire term in a l on b lo w e r
speed sw itch c o n n e cto r w ith
12 v o lt test lig h t.
r
|G R O U N D O K | | b a d g r o u n d | |L A M P L IG H T S |
1
Replace relay
R epair ground
Repair open
in w ire fro m
blow e r speed
sw itch to relay.
i
L A M P DOES
N O T L IG H T
W ith ig n itio n sw itch in &quot; R u n ” p o s itio n , and A /C &quot; O n &quot; , connect
tester and locate s h o rt in one o f the fo llo w in g w ires or co m p o &shy;
nents. Replace a shorted w ire o r defe ctive sw itch .
C-K M O D E L S YSTEM S
1. W ire fro m fuse panel to m aster sw itch (on c o n tro l).
2. Master sw itch .
3. W ire fro m m aster sw itch to th e rm o sta tic sw itch .
4. T h e rm o sta tic sw itch .
5. W ire fro m th e rm o s ta tic sw itch to discharge pressure sw itch .
6. Discharge pressure sw itch .
7. W ire fro m discharge pressure sw itch to com pressor clu tc h
solenoid.
G M O D E L SYSTEM S
1. W ire fro m fuse panel to blow e r sw itch .
2. B low er sw itch .
3. W ire fro m b lo w e r sw itch to th e rm o s ta tic sw itch .
4. T h e rm o sta tic sw itc h .
5. W ire fro m th e rm o sta tic sw itch to the rm a l fuse.
6. Therm al fuse.
7. W ire fro m the rm a l fuse to com pressor c lu tc h solen oid.
M O TO R H O M E U N IT
1. W ire fro m fuse panel to blow e r sw itch .
2. B low e r sw itch .
3. W ire fro m b lo w e r sw itch to th e rm o s ta tic sw itch .
4. T h e rm o sta tic sw itch .
5. W ire fro m th e rm o s ta tic sw itch to com pressor clu tc h
solenoid.
1
Replace
B lo w e r speed
sw itch .
LIGHT
DUTY
TRUCK
* S h o rt c irc u it m ay be in te rm itte n t.
If tester does n o t indicate a s h o rt c irc u it,
m ove harness arou nd as m uch as possible
to re-create sh o rt c irc u it. W atch and
listen fo r arcing.
SERVICE
**R e fe r to W iring Diagrams w hile performing
the follow ing checks.
M ANUAL
Fig. 103-Electrical System Diagnosis Chart
|P O O R OR NO G R O U N D l
Repair ground
X
NO C L IC K H E A R D
( G R O U N D 0~iT|
Disconnect conn ector on
com pressor clu tc h solenoid
and a p p ly 12 vo lts to solenoid.
C LIC K H E A R D
Replace solenoid
W ith ig n itio n sw itch in &quot; R u n &quot; p o s itio n and A /C &quot; O n &quot; , check
fo r defective sw itch at the fo llo w in g locations. Using an exte rnal
ju m p e r w ire , d isco nnect the electrical lead at the sw itch and
ju m p the sw itch te rm in a ls (see &quot;W irin g D iagra m s&quot;).
C-K M O D E L SYS T E M
1. Master S w itch .
2. T h e rm o sta tic S w itch .
3. Discharge Pressure S w itch .
G M O D E L SYS T E M
1. B low e r sw itch .
2. T h e rm o sta tic S w itch .
3. T herm al fuse (See &quot; L o w R e frig e ra n t Charge P ro te ctio n System
D iagn osis&quot;).
M O T O R H O M E U N IT
1. B low e r sw itch .
2. T h e rm o sta tic sw itch .
N O T E : If th e com pressor is still in o p e ra tive a fte r the above
checks, check fo r pow er feed at each co m p o n e n t since
tw o or m ore co m p o n e n ts are defe ctive or there is an
open in the w ires co nn ecting the com p onents.
C O N D IT IO N IN G
W ith ig n itio n sw itch in the
&quot; R u n &quot; p o sitio n and the
heater o r A /C on, m ove the
blow e r speed sw itch to H i.
Relay &quot; c lic k &quot; should be
heard when sw itch is m oved.
AIR
Check C om pressor S ole noid G round
HEATER A ND AIR C O N D IT IO N IN G
1A-85
LOW R EFR IG ER A N T CHARGE PROTECTION SYSTEM DIAGNOSIS
CHECK LIST SHOWING POSSIBLE CAUSES AND
SUGGESTED CORRECTIONS FOR BLOWN THERMAL FUSE*
CAUSE
CORRECTION
Low refrigerant charge or totally discharged system .
Inspect for leaks, repair, evacuate, recharge system
and th en replace therm al fuse.
Inoperative expansion valve. (See Service Diagnosis
chart.)
Replace expansion valve according to norm al
procedures, recharge system and then replace the
therm al fuse.
U nderhood tem peratures exceeded 26 0&deg;F.
Install new therm al fuse.
Therm al fuse blow n during charging.
Jum p connector plug “ B” &amp; “ C ” term inals during
charging and replace therm al fuse.
F aulty Superheat Switch.
Replace superheat sw itch according to proced ure,
recharge system and replace therm al fuse.
G rounded Superheat Switch.
Repair ground condition and replace therm al fuse.
New Therm al Fuse Blows Im m ediately.
Check for and correct as follows:
A. Pinched, broken or bare wires.
B. Boot off of connector at switch.
C. Connector on thermal limiter reversed.
D. Connector shorted to switch body.
E. Refrigerant pipes cutting through boot at switch.
F. Connector off center on switch pin.
*Due to Superheat Sw itch Sensing A bnorm al System C ondition and Protecting System .
LIGHT DUTY TRUCK SERVICE MANUAL
1A-86 HEATER AND AIR C O N D IT IO N IN G
LOW R EFR IG ER A N T CHARGE PROTECTION SYSTEM
CHECK
CHECK FOR
Supply voltage at clutch coil term inals.
E L E C T R IC A L
(Com pressor Inoperative, Engine
Running, A/C Selector Switch “ O N ” ,
Therm al Fuse D isconnected).
Blown fuse at m ain circuit fuse panel.
Voltage therm al fuse term inal “ B ” to ground. (If no voltage check
for broken lead, loose or poor connections or open am bient
switch.)
Voltage, therm al fuse term inal “C ” to ground. (If no voltage,
therm al fuse is blow n. If voltage present, check therm al fuse to
clutch coil lead and connections.)
THERM AL FUSE
(Com pressor Inoperative, Engine
Running. A/C Selector Switch
“ O N ”, Therm al Fuse D isconnected).
SUPERH EAT SWITCH
(Engine “ O F F ” , l e a d
disconnected from Superheat
Sw itch term inal).
C ontinuity betw een term inals “ B” and “ C” . (If no continuity,
fuse link is blow n, repair system and replace therm al fuse.)
Resistance, term inals “ S” to “ C ” to be 8.4 to 10.4 ohm .
(If no t w ithin lim its, replace therm al fuse.)
C ontinuity betw een sw itch housing and ground. (If no t grounded,
check continuity, sw itch housing to retainer ring and retainer ring
to rear head.)
C ontinuity betw een sw itch term inal and sw itch housing. (If no
continuity, contacts are open. If continuity exists, contacts are
closed.)
Install suction gauge and determine the suction pressure, determine
the approxim ate rear head tem perature and com pare conditions
noted to calibration chart. If contacts are n o t open or closed
according to tem perature-pressure relations show n, discharge
system and rem ove switch for bench check.
SU PERHEAT SWITCH
Closed contacts - (Housing to term inal contacts should be open
at atm ospheric pressure and tem peratures below 1 0 0 &deg;F.)
(Switch Off Com pressor)
A lternate
Closed contacts (w ith sw itch in a h o t bath 15 0&deg;F . or above).
Closed contacts (w ith sensing tube held in m atch flam e for 15-20
seconds).
Note: If switch contacts are not “OPEN” or “CLOSED” per these checks, the switch is defective and must be replaced.
LIGHT DUTY TRUCK SERVICE MANUAL
HEATER AND AIR C O N D IT IO N IN G
selector lever positions, a leak is indicated in
these circuits.
VACUUM SYSTEM DIAGNOSIS
(C-K FOUR-SEASON SYSTEM)
Start the engine and allow it to idle - move the selector
lever to each position and refer to the vacuum diagrams
and operational charts for proper airflow, air door
functioning and vacuum circuits. If airflow is not out of
the proper outlets at each selector lever position, then
proceed as follows:
1. Check for good hose connections-at the vacuum
actuators, control head valve, reservoir, tees, etc.
2. Check the vacuum source circuit as follows:
Install vacuum tee and gauge (with restrictor) at the
vacuum tank outlet (see Vacuum Daigram). Idle the
engine and read the vacuum (a normal vacuum is
equivalent to manifold vacuum) at all selector lever
positions.
a. Vacuum Less Than Normal At All PositionsRemove the tee and connect the vacuum gauge
line directly to the tank - read the vacuum. If
still low, then the problem lies in the feed circuit,
the feed circuit to the tank or in the tank itself.
If vacuum is now normal, then the problem lies
downstream.
b. Vacuum Less Than Normal at Some PositionsIf vacuum was low at one or several of the
1A-87
c.
3.
4.
Vacuum Normal at All Positions-
If vacuum was normal and even at all positions,
then the malfunction is probably caused by
improperly connected or plugged lines or a
defective vacuum valve or valves.
Specific Vacuum Circuit Check
Place the selector lever in the malfunctioning
position and check for vacuum at the pertinent
vacuum actuators. If vacuum exists at the actuator
but the door does not move, then the actuator is
defective or the door is mechanically bound. If low
or no vacuum exists at the actuator, then the next
step is to determine whether the cause is the vacuum
harness or the vacuum valve. Check the vacuum
harness first.
Vacuum Harness Circuit Check
a. Disconnect the vacuum harness at the control
head.
b. The black line (# 1 ) should show engine vacuum
- if not, trace back through connector to vacuum
tank.
c. To check any individual circuit place the selector
lever at the involved circuit position and check
for vacuum presence.
LIGHT DUTY TRUCK SERVICE MANUAL
1A-88
HEATER
BLOWER MOTOR
•BLK-
THERMOSTATIC
SWITCH
AND
DISCHARGE
PRESSURE
SWITCH
AIR
LIGHT
DUTY
TRUCK
SERVICE
M ANUAL
Fig. 104-Four-Season System Wiring Diagram (C-K Models)
POS
CIRCUIT
OFF
BATT ONLY
MED 1
BATT-M1 -RES
MED 2
BATT-M2-RES
HIGH
BATT BLOWER
C O N D IT IO N IN G
O
HEATER
AND
AIR
DUTY
TRUCK
CONDITIONING
LIGHT
M ANUAL
1A-89
SERVICE
1A-90
HEATER
AND
IGN UNFUSED
10 ORN — 4 2 0 ~ A M P [|~I&raquo;
INLINE FUSE
v s
16 YEL1
■16 ORN-
/l
1
CN
. j I.
RESISTOR
FUSE PANEL
i4 i
I 52 I 5 0 I
51
72
0
52
JHIS BAT
_ !|
POS
CIRCUIT
OFF
B A H O NLY
LO
BATT-LO
MED
BATT-MED
HI
BATT-HI
10 PPL'
LIGHT
BLOWER SWITCH
DUTY
TRUCK
SERVICE
M ANUAL
Fig. 106~0verhead System Wiring Diagram (C-K Models)
BLOWER
MOTOR
C O N D IT IO N IN G
Q
AIR
D
raj
GROUND
-16 BRN
16 BRN — 4~50~
COMPRESSOR
I C V '- ,
-
I.P. WIRING |
| l 5 0 l 59
SUPER
HEAT
SWITCH
JL
HEATER CONTROL
SWITCH CONNECTOR
x
CO
O
^=&gt;—
J
I
Q
z'
O
o
o
J
18 BLK —
r-l
3
'
59 | 59 12021
6
10 ORN-BLK
31
—
w
18 ORN
■p=t
I
•lh
01
J
16 YEL-BLK
BLOWER RELAY
I s ] 60 H
POS
10 ORN-BLK1
16 GRN DK
CIRCUIT
OFF
B A H . O NLY
LO
BATT. LO
B A H . LO, MED
HI
B A H . L, M, HI
DUTY
TRUCK
CONDITIO NING
LIGHT
JUNCTION
BLOCK
16 YEL
■16 GRN DK
DASH
M ANUAL
1A-91
SERVICE
TEMPERATURE
CONTROL
SWITCH
(THERMOSTATIC SWITCH)
Fig. 107 -Floor M ounted System W irin g Diagram (G M odels)
AIR
MED
AND
*
10 BLK-ORN
HEATER
THERMAL
FUSE
CIRCUIT
BREAKER
&laquo;=&lt;&sect;)
1A-92
HEATER
BLOWER RELAY
(REAR)
AND
AIR
C O N D IT IO N IN G
GRD
LIGHT
DUTY
TRUCK
TIE RELAY
(FRONT TO
SERVICE
REAR)
BLOWER SWITCH (FRONT)
POS
CIRCUIT
OFF
B A H . O NLY
LO
B A H . LO
MED.
BAH
HI
B A H . L, M, HI
LO, MED
BLOWER SWITCH (REAR)
M ANUAL
Fig. I08-Floor 0verhead System Wiring Diagram (G Models)
BLOWER
MOTOR
(REAR)
■
fl
| TO FUSE PANEL
GROUND
COMPRESSOR
RESISTOR
N TO 1 A 4
HIGH
N TO 1, 3 4 4
DUTY
TRUCK
CONDITIONING
N TO I &amp; 2
MED
AIR
N TO NONE
LOW
AND
LIGHT
THERMOSTATIC
SWITCH
BLOWER
SWITCH
CONNECTION
OFF
HEATER
BLOWER SWITCH
SET AT
1A-93
SERVICE
M ANUAL
Fig. 109-Motor Home Chassis Wiring Diagram
1 A-9 4 HEATER A N D AIR C O N D IT IO N IN G
SPECIAL TOOLS
1.
2.
2A.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Charging Station
Oil Inducer
Super Heat Switch
Remover
J-5453
Goggles
90 Degree Gauge Line
J-9459
Adapter
Gauge Line Adapter
J-5420
Leak Detector
J-6084
Puller
J-8433
Puller Pilot
J-9395
J-23595 Refrigerant Can Valve
(Side-Tap)
Refrigerant Can Valve
J-6271
(Top-Tap)
Pocket Thermometers (2)
J-5421
J-8393
J-24095
J-9393
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
J-5403
J-643 5
J-9396
No. 21 Snap Ring Pliers
No. 26 Snap Ring Pliers
Compressor Holding
Fixture
J-9397
Compressing Fixture
J-9403
Clutch Hub Holding Tool
J 9399
9/16&quot; Thin Wall
Socket
J-9401
Hub and Drive Plate
Assembly Remover
J 9480
Hub and Drive Plate
Assembly Installer
J 9392
Seal Remover
J-23128 Seal Seat Remover
J 9398
Pulley Bearing Remover
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
J-9481
Pulley and Bearing
Installer
J-8092
Handle
J-21352 Internal Assembly
Support Block
J-5139
Oil Pickup Tube
Remover
J-9432
Needle Bearing Installer
J-9553
Seal Seat &quot;O ” Ring
Remover
J-21508 Seal Seat &quot;O ” Ring
Installer
J-22974 Shaft Seal Protector
J 9527
Pressure Test Connector
J-9402
Parts Tray
Fig. 110- Air Conditioning Special Tools
LIGHT DUTY TRUCK SERVICE MANUAL
SECTION IB
BODY
The following caution applies to one or more steps in the assembly
procedure of components in this portion of the manual as indicated at
appropriate locations by the terminology &quot;See Caution on page 1 of this
Section&quot;.
CAUTIO N : THIS FASTENER IS AN IM PORTANT ATTACHING
PART IN THAT IT COULD AFFECT THE PERFORMANCE OF
VITAL COMPONENTS AND SYSTEM S, AND /O R COULD RESU LT
IN MAJOR REPAIR EXPENSE. IT M U ST BE REPLACED WITH
ONE OF THE SAME PART NUMBER OR WITH AN EQUIVALENT
PART IF REPLA CEMENT BECOMES NECESSAR Y. DO NOT USE A
REPLACEMENT PART OF LESSER QUALITY OR SUBSTITUTE
DESIGN. TORQUE VALUES M U ST BE USED A S SPECIFIED
DURING REASSEM BLY TO ASSU RE PROPER RETENTION OF
THIS PART.
CONTENTS OF THIS SECTION
General Description........................................................................
C-K Models.......................................................................................
G Models...........................................................................................
Special Tools.....................................................................................
IB-1
IB-4
IB-30
IB-48
GENERAL DESCRIPTION
On the following pages, service procedures will be given
for components on all 10-20-30 series trucks in C, K and
G models. Reference will be made, both in text and
illustrations, to vehicle model lines and to individual
model numbers within these model lines.
As an aid to identification of specific models, the
following general descriptions are given.
Chassis/Cabs
All chassis/cabs use &quot;03&quot; as the model identification. See
figure 1. Two-wheel drive units come in C-10, C-20 and
C-30 series. Four-wheel drive units may be either K-10
or K-20. Optional pickup boxes are available.
Crew Cab/Chassis
Model number &quot;63&quot; designates the crew cab/chassis
models. See figure 2. Optional pickup boxes are
available.
Fig. 1—Typical Chassis/Cab
LIGHT DUTY TRUCK SERVICE MANUAL
1 B-2 BODY
Fig. 3—Typical Coach
Coach
The four-door coach model number is &quot;06&quot;. See figure 3.
Base models have rear cargo doors. An optional endgate
with moveable window is available.
Utility
Utility models are designated with the number &quot;14&quot;. See
figure 4. An optional removable roof is also available.
Vans
G-Series Vans are available in two model number
designations. See figures 5 and 6. Vans without body
windows use number &quot;05&quot;; vans with body windows are
&quot;06&quot; models.
Fig. 4—Typical Utility Vehicle
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1 B-3
Fig. 6—Typical &quot;0 6 &quot; Van
LIGHT DUTY TRUCK SERVICE MANUAL
I B 4 BODY
C-K MODELS
INDEX
Front End
Windshield W ipers...................................................... IB-4
Glove Box....................................................................... IB-5
Rear View Mirrors...................................................... IB-5
Body Glass
Windshield Glass......................................................... IB-6
Stationary Body G lass............................................... IB-8
Side Doors
Adjustments....................................................................
Front Side D oor..........................................................
Replacement...............................................................
H inges.........................................................................
Ventilator....................................................................
Window and Regulator........................................
Locks, Handles, Rods.............................................
W eatherstrip.............................................................
Rear Side Doors..........................................................
IB-9
IB-10
IB-10
IB-10
IB-10
IB-11
IB-12
IB-14
IB-14
Replacement...............................................................
H inges..........................................................................
Stationary G lass.......................................................
Window and Regulator.........................................
Locks, Handles, Rods.............................................
W eatherstrip..............................................................
IB-14
IB-14
IB-14
IB-14
IB-15
IB-16
Rear Doors
Adjustments.................................................................... IB-16
Locks, Handles, Rods................................................. IB-17
Hinges................................................................................ ib -18
Gates
Endgates.............................................................................IB-19
Tailgates.............................................................................IB-23
Removable Top (U tility ) ................................................ ..IB-24
S eats ..................................................................................... ..IB-25
Body M ou n tin g ................................................................. ..IB-26
FRONT END
WINDSHIELD WIPERS
Windshield wiper units on all models are of the twospeed electric type. A single wiper motor unit, mounted
to the left side of the dash panel inside the engine
compartment, powers both wiper blades. The wiper blade
operating link rods and pivot mountings on these models
are located in the outside air inlet plenum chamber.
Arm Adjustment
To adjust sweep of blades, turn on wipers and note
sweep of arms. If necessary, remove one or both arms as
follows: Pull outer end of arm away from glass which
will trip lock spring at base of arm and release spring
from undercut of pivot shaft. While holding arm in this
position, pull outward on cap section at base of arm to
remove arm. Arm can be reinstalled in any one of
several positions due to serrations on pivot shaft and in
arm cap. See figure 7.
Installation
1. Place wiper linkage and transmission into position.
Secure assembly with two screws at each
transmission.
2. Attach end of cross rod to drive arm of motor
assembly. Secure rod.
3. Before installing wiper arms, operate wiper motor
momentarily which should rotate pivot shafts to
park position. Install arms and shafts.
Wiper Arm Pivot Shafts and Linkage
Removal
1. Remove windshield wiper arms from pivot shafts.
Procedure for removing arms is explained previ&shy;
ously under &quot;Arm Adjustment&quot;.
2. Remove two nut and lock washer assemblies from
the connector link to motor drive arm via the
plenum access hole.
3. Remove two screws from each transmission pivot
shaft assembly to windshield frame. Remove wiper
linkage and transmission from plenum.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
Fig. 8 —Glove Box
INSTRUMENT PANEL COMPARTMENT AND
LOCK
Replacement
Removal of the entire assembly including door may be
accomplished by removing four screws which attach
hinge just below box. See figure 8. The outer door panel
may be removed, leaving the compartment intact, by
removal of four screws. Access to the door stop bumper
is gained by reaching into compartment opening with
door partially open.
Fig. 9—Rear View Mirror—Base
IB - 5
Fig. 10—Rear View Mirror—Below Eyeline
Adjustment
Engagement of lock in striker may be adjusted by
loosening striker retaining screws and moving the striker
to desired position.
OUTSIDE REAR VIEW MIRRORS
Rear view mirror installations are shown in figures 9, 10
and 11. Occasional tightening of mounting and assembly
bolts and screws will sharply decrease occurrence of
failure due to door slamming or road shock.
Fig, 11—Rear View Mirror—West Coast
1 B-6 BODY
INSIDE REAR VIEW MIRROR—FIG. 12
Replacement
1. Remove screw retaining mirror to its glass-mounted
bracket and remove mirror.
2. Install mirror into its mounting bracket. Torque
screw to specifications.
NOTE: Camper mirror installation is similar
to the below eyeline mirror installation.
Fig. 12—Inside Rear View Mirror
BODY GLASS
WARNING:
dling glass.
Always wear gloves when han&shy;
WINDSHIELD GLASS
The windshield is a one-piece type and is retained in the
windshield opening by a moulded rubber weatherstrip.
See figure 13.
When replacing a cracked windshield glass, it is very
important that the cause of the glass breakage be
determined and the condition corrected before a new
glass is installed. Otherwise, it is highly possible that a
small obstruction or high spot somewhere around the
windshield opening will continue to crack or break the
newly installed windshield especially when the strain on
the glass caused by this obstruction is increased by such
conditions as wind pressures, extremes of temperature,
motion of the vehicle, etc.
NOTE: The procedure for removal of the
windshield applies to other stationary glass
applications, such as in figures 20 and 21.
Removal
VIEW A
Fig. 13—Typical Windshield
1. Before removing the windshield, mark the location
of the break on the windshield rubber channel and
the body. Protect the paint finish inside of the cab.
Mask around the windshield opening and outside,
lay a suitable covering across the hood and fenders.
NOTE: The windshield glass rubber
weatherstrip is one piece. The glass is held
in a channel within the weatherstrip.
2. On vehicles without reveal moldings, &quot;unzip&quot; the
locking strip shown in figure 18.
3. On vehicles with reveal moldings, remove reveal
molding with tools shown in figure 19.
4. To free windshield rubber channel of weatherstrip
loosen the lip of the windshield weatherstrip from
the pinchweld flange along the top and at the sides
by applying firm, controlled pressure to the edge of
the glass. At the same time assist the lip of the
rubber weatherstrip channel over the pinchweld
flange with a flat bladed tool. See figures 14 and 15.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
Fig. 14—Applying Pressure to Windshield
IB - 7
Fig. 15—Assisting Weatherstrip over Flange
5. With the aid of an assistant outside the cab, remove
the windshield from the opening. See figure 16.
Checking Windshield Opening
Due to the expanse and contour of the windshield it is
imperative in the event of a stress crack that the
windshield opening be thoroughly checked before
installing a replacement windshield. The replacement
glass is used as a template.
1. Check for the following conditions at the previously
marked point of fracture.
a. Chipped edges on glass.
b. Irregularities in body opening.
c. Irregularities in rubber channel weatherstrip.
2. Check flange area for solder, weld high spots, or
hardened spot-weld sealer. Remove all high spots.
3. Check windshield glass to opening, by supporting
glass with six spacers contained in packet J-22577.
See figure 17.
CAU TIO N : Do not strike glass against body
metal. Chipped edges on the glass can lead to
future breaks.
4. With the windshield supported and centered in its
opening, check the relationship of the glass to the
body opening flange around the entire perimeter of
the glass.
5. Check the relationship of glass to opening as
follows:
a. Inside edge of glass to body flange.
b. Outer edge of glass to parallel body metal.
6. Mark areas of body metal or flange to be reformed
remove glass and correct as necessary.
7. Recheck windshield in its opening and if satisfac&shy;
tory proceed as follows.
Fjg 16_ Rem0ving Windshield from Opening
Fig. 17—Checking Windshield Opening
LIGHT DUTY TRUCK SERVICE MANUAL
1 B-8 BODY
Installation
1. Place a protective covering over front fenders and
hood, then apply soapy water to all grooves of the
weatherstrip.
2. Install weatherstrip centrally to the body opening,
with the pinchweld flange in the inner weatherstrip
groove. See figure 18.
NOTE: Because of the configuration of the
weatherstrip and of the importance of
centrally locating the weatherstrip in the
body opening, it is not recommended to use
the &quot;cord-type&quot; installation technique.
3. Position the lower edge of the windshield glass into
the outer weatherstrip groove. Gently push the glass
&quot;into&quot; the weatherstrip, assisting rubber over edge
of glass.
4. When glass is in position, lock the weatherstrip to
the glass as follows.
a. Base W eatherstrip—Bend the &quot;locking strip&quot;
over and use a thin bladed tool to lock
weatherstrip tightly against windshield. See
figure 18 for detail.
b. Optional W eatherstrip—Use J-2189-24 and
J-2189-23 in Handle J-2189 to install flexible
reveal molding into locking slot of weatherstrip,
as shown in figure 19. This will expand the
weatherstrip to a tight fit against the windshield.
Install reveal molding so that joint is at center
of lower edge of windshield. Cover the joint
with the molding cap.
STATIONARY BODY GLASS
Replacement
The method used to remove the windshield glass may be
applied to other stationary glass, such as shown in figures
20 and 21. Remember to check for cause of breakage,
and to always wear gloves when handling glass.
Installation procedures are similar to G-Van windshield.
Refer to figures 9G and 10G, later in this section.
Fig. 19—Installing Reveal Molding
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
BODY SI
DOOR ADJUSTMENTS
Doors can be adjusted for alignment of clearance in the
cab door opening, and for proper latching. Door
alignment adjustments are made at the striker bolt, and
at door hinges. The door, when properly located in door
opening, will have equal clearance around its perimeter.
The door should be adjusted in the opening so the edge
of the door across the top and also at the lock side is
parallel with the body opening as nearly as possible.
1 B-9
DOORS
bolt, adjust to desired height, and tighten bolt
securely.
NOTE: This adjustment is im portant to
Hinge Adjustment
Door hinge bolt holes are oversized to make adjustment
possible. Alignment adjustments can be made by
loosening the proper hinge bolts, aligning door to proper
position, and tightening bolts securely. See figure 22, for
typical adjustments.
Striker Bolt Adjustment
W ith the use of J-23457, shown in figure 23, the striker
bolt can be adjusted in any of three ways. See figure 24.
1. Up and down—To adjust striker up or down, loosen
LIGHT DUTY TRUCK SERVICE MANUAL
I B - 1 0 BODY
assure that the right proportion of door’s
weight will rest on striker bolt when door is
closed. If bolt is positioned too high on pillar,
rapid wear will occur to the lock cam; if too
low, an extra load will be placed on door
hinges as well as pull door downward and out
of alignment.
2. In and Out—To adjust striker in and out, loosen
bolt, adjust horizontally to desired position and
tighten bolt securely.
3. Forward and Rearward—To make this adjustment,
loosen striker bolt, shim to desired position, and
tighten bolt securely.
FRONT DOOR ASSEMBLY
DOOR HINGE
The door check is part of the front door upper hinge.
The front door torque rod check holds the door in either
of two positions between full open and closed. The front
door check-hinge assembly is replaced as a complete unit
as follows. See figure 22.
Removal
1. Loosen front fender rear bolts.
2. With special Tool J-22585 remove 3 bolts securing
front door upper hinge to cowl pillar.
a. Remove the door to upper hinge retaining bolts.
b. With aid of an assistant to support weight of
door, remove the door to lower hinge retaining
bolts and remove door.
Replacement
Remove the door assembly from the body by removing
the hinges from the door.
Installation
1. Install hinge snugly on pillar in same location as
hinge removed.
2. With the aid of an assistant fasten the door to the
hinge.
3. Adjustment of the door lock and striker plate
should be made after the door is positioned in the
opening.
DOOR VENTILATOR ASSEMBLY—FIG. 25
Removal
Fig. 23—Loosening Striker Bolt
NOTE: The channel between the door
window glass and door vent is removed as
part of the vent assembly.
1. Regulate the door window glass to the full down
position.
2. Remove clip from the window regulator handle,
and knob from lock rod.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
3. Remove arm rest screws and trim panel. See figure
26.
4. Remove screws attaching ventilator lower assembly
to door panel.
5. Loosen inner to outer panel attaching screw
through access hole just rearward of the lower vent
pivot.
6. Slide door window glass rearward away from
ventilator.
7. Remove three screws at the upper front of the door
frame.
8. Turn vent assembly 90&deg; and carefully remove by
guiding up and out. See figure 27.
Ventilator Glass Replacement
l . Using an oil can or similar means, squirt prepsol or
equivalent on the glass filler all around the glass
1B-11
channel or frame to soften the old seal. When the
seal has softened, remove the glass from the
channel.
2. Thoroughly clean the inside of the glass channel
with sandpaper, removing all rust, etc.
3. Using new glass channel filler, cut the piece to be
installed two inches longer than necessary for the
channel. Place this piece of filler (soapstoned side
of filler away from glass) evenly over the edge of
the glass which will fit in the channel. The extra
filler extending beyond the rear edge of the glass
should be pinched together to hold it in place
during glass installation.
NOTE: One side of this filler (the outside of
the roll) is soapstoned. This is the side which
goes into the metal channel.
4. Brush the inside of the metal glass channel freely
with ordinary engine oil. This will enable the glass
and filler to slide freely into the channel. Push the
glass with the filler around it into the channel until
it is firmly seated. After the glass is firmly in place,
the oil softens the filler, causing it to swell, thereby
making a watertight seal. Trim off the excess filler
material around the channel and at the ends of the
channel.
NOTE: Glass should be installed so that rear
edge is parallel to the division post. Allow
full cure before water testing.
Installation
1.
2.
3.
4.
5.
NOTE: Replace the door window glass and
regulate to the full down position before
installing the door ventilator assembly.
Lower the ventilator assembly into the door frame.
Make certain the rubber lip is positioned inside the
inner and outer panel before tightening screws.
Slide door glass forward engaging glass in vent
channel.
Reinstall all screws and tighten.
Install and tighten the three screws at the upper
front of the door.
Adjustment
1. Adjust the ventilator by placing wrench on
adjusting nut thru access hole and turning vent
window to the desired tension. See figure 28.
2. After making adjustment bend tabs over the hex
nut on base of assembly. See figure 29.
3. Install arm rest screws and trim panel.
4. Install window regulator handle.
DOOR WINDOW ASSEMBLY—FIG. 30
Fig. 27—Removing Ventilator Assembly
Replacement
1. Completely lower glass to bottom of door.
LIGHT DUTY TRUCK SERVICE MANUAL
1B-12 BODY
TO ADJUST T E N S IO N S
TURN THE VENT WHILE
HOLDING A WRENCH
O N THE HEX NUT____
Fig. 30—Door Window and Regulator
Fig. 28—Adjusting Tension
2. Remove window regulator handles using tool
J-7797.
3. Remove door arm rest and trim pad.
4. Mask or cover upper portion of door window
frame. Remove ventilator assembly as previously
outlined.
5. Slide glass forward until front roller is in line with
notch in sash channel. Disengage roller from
channel.
6. Push window forward and tilt front portion of
window up until rear roller is disengaged. See figure
31.
7. Put window assembly in normal position (level) and
raise straight up and out.
8. Reverse above procedure for installation.
WINDOW REGULATOR—FIG. 30
Replacement
1. Remove ventilator assembly and door window as
outlined previously.
2. Remove screws attaching regulator to door inner
panel.
3. Remove regulator assembly through door opening.
4. Install regulator by reversing above steps. Lubricate
regulator gear with lubriplate or equivalent.
LOCKS, HANDLES AND RODS
The door lock, handles and control rods are shown in
figure 32 as they would be installed in the vehicle. Note
the clips which attach the three control rods to the lock
assembly.
NOTE: All clips which attach control rods to
lock assembly must be replaced whenever
removed.
BEND TAB OVER
HEX NUT
no tch
ijl
ROLLER
Fig. 29—Bend Tabs Over Hex Nut
Fig. 31—Removing Door Glass
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-13
Door Lock Assembly
Replacement
1.
2.
3.
4.
5.
6.
Raise window to gain access to lock.
Remove regulator handle.
Remove remote control push button knob.
Remove trim panel.
Remove clip from inside handle rod-to-lock.
Remove clip from outside handle rod-to-lock. This
is best accomplished by inserting a long screwdriver
through the daylight opening, as shown in figure 32.
7. Remove screws which attach lock assembly to door
panel.
8. Remove lock and remote control rod as an
assembly.
9. To install lock assembly, reverse above steps. Be
sure to replace all clips removed earlier.
Door Outside Handle—Fig. 33
Replacement
1.
2.
3.
4.
5.
6.
Raise window to gain access to lock.
Remove window regulator handle.
Remove remote control rod.
Remove trim panel.
Remove clip from outside handle rod-to-lock.
Remove screws which retain outside handle to door
panel.
7. Remove handle and control rod.
8. Reverse above procedures to install outside handle.
Door Lock Cylinder—Fig. 33
Replacement
l . Raise door window.
2. Remove window regulator handle, remote control
knob and trim panel.
3. Use a screwdriver or other suitable tool to slide the
lock cylinder retaining clip out of engagement with
the lock cylinder.
4. Remove lock cylinder.
5. To install, reverse the above steps.
Door Inside Handle
Replacement
1. Remove window regulator handle, remote control
push button knob and trim panel.
2. Disconnect control rod from inside handle, as
shown in figure 34.
3. Remove screws retaining inside handle to door.
4. Remove inside handle.
5. Reverse above steps to install.
LIGHT DUTY TRUCK SERVICE MANUAL
1B-14 BODY
DOOR TO BODY OPENING
WEATHERSTRIP—FIGS. 35, 36
Side door sealing incorporates an inner seal. The inner
seal is mounted on the body opening welding flange and
goes completely around the periphery of the opening.
The molded weatherstrip material is snapped in place.
Success of weatherstrip replacement depends entirely
upon the quality of the cement used and the care with
which it is applied. All rust, road dirt and grease or oil
must be completely removed as as should all old cement
and bits of old weatherstrip. After removing all foreign
material from door opening surface proceed as follows:
1. Open door and block open.
2. Remove sill plate retaining screws and remove sill
plate.
3. Remove side door inner weatherstrip seal.
4. Install molded corner of inner weatherstrip, starting
at the bottom of the door opening.
5. Trim inner weatherstrip with a notch and butt ends
together.
6. Reinstall sill plate and sill plate retaining screws.
Fig. 36—Door Weatherstrip (14)
REAR SIDE DOOR (06 AND 63 ONLY)
Adjustments and Hinge Replacement
The procedures for hinge replacement, and for hinge
and striker bolt adjustment are similar to those detailed
in the front door adjustment procedure. Access to the
hinges of the rear door is shown in figure 37.
STATIONARY GLASS-REAR DOOR
Replacement
1. Lower window to full down position.
2. Remove remote control knob and window regulator
handle.
3. Remove screws retaining door trim pad, and
remove trim pad. See figure 38.
4. Remove glass run channel by removing screws
retaining channel to door. See figure 39.
5. Remove stationary glass.
6. Replace glass by reversing above procedure.
WINDOW GLASS—FIG. 40
Replacement
1. Lower glass to full down position.
2. Remove remote control push button knob, window
regulator handle and trim pad.
3. Remove stationary glass as previously outlined.
Remove screws from rear division channel, and
slide channel rearward in the opening.
4. Raise glass as far as possible, then slide glass until
the roller is in line with the notch in the sash
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
channel. See figure 40. Disengage roller from
channel.
5. Tilt window outboard and move until other roller
can be removed from channel.
6. Raise window up and out.
7. Reverse above procedure for installation.
IB -1 5
4. Install regulator by reversing above procedure.
Lubricate regulator gear with lubriplate or
equivalent.
LOCKS, HANDLES AND RODS
Lock Assembly—Fig. 41
Replacement
WINDOW REGULATOR ASSEMBLY—FIG. 40
Replacement
1. Remove trim pad, stationary glass, and window
glass as outlined earlier.
2. Remove screws attaching regulator assembly to
door inner panel.
3. Remove regulator assembly through opening in
door.
1. Remove window regulator handle and remote
control push button knob.
2. Remove trim pad.
3. Disengage three clips which retain control rods to
lock assembly.
a. Inside handle control rod.
b. Remote control lower rod.
c. Outside handle control rod.
4. Remove screws retaining lock assembly to door
panel, then remove lock assembly.
5. Install lock by reversing above procedure. Be sure
to replace all clips removed with new clips on
installation.
Inside Handle—Fig. 41
Replacement
Fig. 39—Glass Run Channel
1. Remove regulator handle, remote control knob and
trim pad as outlined previously.
2. Disconnect control rod from inside handle by
removing clip as shown in figure 41.
3. Remove inside handle by removing four screws
which secure handle to door panel.
4. Replace handle by reversing above procedure.
Install new clip when installing control rod.
LIGHT DUTY TRUCK SERVICE MANUAL
1B-16 BODY
3. Remove two screws securing outside handle to door
panel.
4. Remove handle assembly.
5. Replace by reversing above procedure. Be sure to
use new clip when attaching control rod to lock
assembly.
WEATHERSTRIP—FIG. 44
The procedure outlined in Front Door W eatherstrip may
be applied to the Rear Side Door W eatherstrip, shown in
figure 44.
REAR DOORS (06 ONLY)
Adjustments
Fig. 41—Lock Assembly and Inside Handle
Rear doors may be adjusted in the body opening by
loosening hinge bolts and repositioning door, then
retightening bolts. See figure 47 for hinge bolt location.
Remote Control—Fig. 42
Replacement
1. Remove regulator handle, remote control knob and
trim pad.
2. Disconnect remote control lower rod from door lock
assembly.
3. Remove two screws securing each remote control
lever to door panel.
4. Remove remote control levers and rods through
door opening.
5. Replace by reversing above procedure.
Outside Handle—Fig. 43
Replacement
1. Remove regulator handle, remote control rod and
trim pad.
2. Disengage outside handle control rod from lock
assembly by removing clip, as shown in figure 43.
Fig. 42—Remote Control Assembly
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
IB -1 7
Fig. 45—Rear Door Controls
LOCKS, HANDLES AND RODS
The rear door lock, outside handle, lock cylinder, control
rods and latch are shown in figures 45 and 46. The rods
can be disconnected from the lock, latch or handle by
disengaging the retaining clips, as shown. The lock
cylinder is removed in the same m anner as the front side
door lock cylinder.
Fig. 46—Rear Door Outside Handle and Lock
Cylinder
LIGHT DUTY TRUCK SERVICE MANUAL
I B - 1 8 BODY
WEATHERSTRIP
W eatherstrip installation is shown in figures 48 and 49.
Proper installation is dependent on completely cleaning
all foreign material from old installation and using a
quality cement on the new installation.
REAR
D O O R —F IG . 47
Replacement
1. Remove bolts securing check arm bracket to body
pillar.
2. Remove upper and lower hinge bolts, and with aid
from an assistant, remove the rear door.
3. Reverse above steps for reinstallation.
Fig. 48—Weatherstrip—L.H. Rear Door
C H E C K A R M —F IG . 4 7
Replacement
1. Remove bolts securing check arm bracket to body
pillar.
2. Remove check arm access cover.
3. With one hand supporting housing assembly and
insulator on the inside of the door panel, remove
bolts securing housing assembly to door.
4. Remove housing, insulator and check arm.
5. To separate check arm from bracket, remove
holding pin connecting the two parts.
6. To install check arm, reverse the procedure above.
Fig. 49—Weatherstrip—R.H. Rear Door
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-19
ENDGATES (0 6 A N D 14)
Coach models (06) and utility models (14) use endgates
of similar, yet distinct design. Separate procedures follow
for service on each of these endgates.
ENDGATE ASSEMBLY(06) MODELS ONLY
Replace
1. Lower endgate, and remove hinge access covers. See
figure 50.
2. Remove endgate-to-hinge bolts.
3. Remove L.H. torque rod bracket, shown in figure
51.
4. Lift endgate to almost closed position and remove
support cables.
5. Remove endgate with torque rod.
6. To install, reverse removal procedure.
HINGES
Replacement
If necessary to remove hinges, remove endgate as
outlined previously, and proceed as follows:
1. Remove bolts from each of the hinge assemblies on
the underside of the body. See figure 50.
2. Remove hinge assemblies. If the hinge pins are to
be removed, note the position of bushings so they
may be reinstalled in the same position.
3. Reverse procedure to install.
Fig. 50—Endgate, Hinges and Supports—(06 Only)
Fig. 51—Torque Rod—(06 Only)
ENDGATE DISASSEMBLY
1. Remove access cover shown in figure 52, to gain
access to interior components.
2. Detach remote control rods from lock assembly by
removing clips.
3. Remove bolts securing lock assembly, and remove
lock assembly.
4. Remove handle assembly bolts and remove inside
handle.
5. Remove R.H. torque rod bracket screws, figure 51,
then remove torque rod from endgate.
6. Remove screws connecting cam assemblies to sash
assembly, figure 53, then remove cam assemblies.
7. Remove glass from endgate.
Fig. 52—Latch and Remote Controls—(06 Only)
LIGHT DUTY TRUCK SERVICE MANUAL
1B-20 BODY
Fig. 53—Window Glass and Regulator—(06 Only)
8. Unclip and remove inner and outer seal assemblies.
9. Remove screws connecting window regulator
assembly to endgate, figure 53, and remove
regulator.
10. From inside the endgate, remove the nuts fastening
the outside handle to endgate and remove the
outside handle. See figure 54.
NOTE: If equipped with power tailgate
window, detach wiring harness from motor.
11. Remove side bolts connecting left and right glass
channels to endgate and remove channels.
12. Remove side latch bolts and remove side latches
with control rods. See figure 52.
NOTE: Detach wiring harness from R. H.
latch if so equipped.
13. Separate side latch from control rod by pulling
control rod thru nylon guide.
14. Reverse the above procedure for reassembly and
installation.
Fig. 54—Outside Handle (06 and 14)
ENDGATE ASSEMBLY—
(14) MODELS ONLY
Replacement
1. Lower endgate, then remove four bolts securing
hinge to body on each side. See figure 55.
2. Disconnect torque rod anchor plate on each side. It
is necessary to remove lower bolt only, then let
plate swing down. See figure 59.
3. With an assistant, raise endgate part way, then
Adjustments
Loosen bolts, adjust at either endgate hinge position or
endgate latch, then retighten bolts.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
IB -2 1
disconnect support cables from endgate. See figure
55.
4. Remove endgate by pulling disconnected hinge
from body, figure 56, then grasping torque rod with
one hand and pulling torque rod over gravel
deflector, as shown in figure 57.
5. Individual components may be removed from the
endgate now, or after reinstallation.
6. To install endgate, reverse the above procedure.
HINGE
Replacement
1. Lower endgate and disconnect hinge to be replaced
by removing hinge-to-body bolts. See figure 55.
2. At the other hinge, loosen the hinge-to-body bolts.
3. On the hinge to be replaced, remove the hinge-toendgate bolts.
Fig. 58—Removing Access Cover (14)
4. Pull the endgate away from the body several inches
and withdraw hinge from body. Then lift endgate
slightly to allow removal of hinge from endgate.
See figure 56.
5. To install hinge, reverse the above procedure. Be
sure to install hinge into endgate first, then into the
body.
TORQUE ROD
Replacement
1. Lower endgate and remove access cover, as shown
in figure 58.
2. Disconnect torque rod anchor plate. It is necessary
to remove the lower bolt only, then let plate swing
down. See figure 59.
3. Loosen four bolts retaining endgate hinge to body.
4 Move endgate slightly away from body.
Fig. 56—Pulling Hinge Away From Body (14)
Fig. 57—Grasping Torque Rod (14)
Fig. 59—Torque Rod Installation (14)
LIGHT DUTY TRUCK SERVICE MANUAL
1B-22 BODY
5. Remove torque rod retaining bracket on lower edge
of endgate. See figure 59.
6. Remove torque rod retaining clip on side edge of
endgate.
7. Lift torque rod up and slide from endgate as shown
in figure 60.
8. Reverse the procedure above for installation.
ENDGATE DISASSEMBLY
1. Lower endgate and remove access cover.
2. Disconnect side latch remote control rods from
center control by removing retaining clips. See
figure 61.
3. Remove four screws from each side latch, and
withdraw latch and control rod from endgate, as
shown in figure 62.
4. Disconnect control rod from latch.
5. Refer to figure 63 for installation of latch control
and blockout rod.
6. Disconnect blockout rod from control assembly by
detaching spring and removing two screws retaining
rod to inner panel.
7. Disconnect inside handle control rod from control
assembly, then remove screws which secure inside
handle to inner panel.
8. Remove three screws which retain remote control
assembly to inner panel.
9. Remove control assembly and inside handle as
shown in figure 64.
10. Refer to figure 65 for window and regulator
installation.
11. Roll window to up position.
12. Disconnect sash from regulator as shown in figure
66.
Fig. 60—Removing Torque Rod (14)
Fig. 62—Removing Side Latch
Fig. 61—Latches and Rods
Fig. 63—Control Assembly and Blockout Rod
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
Fig. 64—Removing Control Assembly and Inside
Handle
1B-23
Fig. 66—Disconnecting Sash from Regulator
13. Remove glass from endgate.
14. Remove four regulator attaching screws and
withdraw regulator from endgate as shown in figure
67.
15. Remove outside handle by removing nuts from
inside of outer panel. See figure 68.
16. Reverse the above steps for reassembly.
TAILGATES (03, 63 and 14)
Replacement
Utility vehicles (14) without removable tops utilize a
tailgate shown in figure 69. Chassis/cab (03 and 63)
models have optional pickup units which utilize tailgates
as shown in figures 69 and 70.
The tailgate shown in figure 69 can be removed by
disconnecting both links from the tailgate, removing
Fig. 65—Window and Regulator
Fig. 67—Removing Regulator
Fig. 68—Outside Handle
LIGHT DUTY TRUCK SERVICE MANUAL
I B - 2 4 BODY
screws attaching both trunnions to body, and lifting the
tailgate off the vehicle.
The tailgate shown in figure 70 can be separated from
the vehicle by removing the bolt and lock washer from
each trunnion in carrier box, and removing the tailgate.
REMOVABLE TOP (14 ONLY)
Removal
1. Remove the bracket-to-roof bolt from each of the
top-to-header panel attaching brackets as shown in
Figure 71.
2. Remove the bolts which retain the top to the body
side panels, shown in figure 72.
3. Lower the rear window into the endgate, and lower
endgate.
4. Lower the door windows.
5. Slide top rearward approximately 18&quot; to expose the
bottom rear top-to-pickup box attaching holes.
6. To prevent possible flexing of the sides on removal,
connect the sides of the top with support braces as
follows.
a. Fabricate 2 braces 72&quot; long from wood or
square aluminum tubing. Drill two (2) 3/8&quot;
diameter holes, 63 inches apart in the brace.
b. Attach one brace to the holes exposed in Step 7.
c. Slide top forward to expose the front bottom
top-to-pickup box attaching holes.
d. Attach the second brace to these holes.
7. With assistance, lift the top and move it rearward
for removal.
Fig. 72—Removable Top
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
SEATS
Care and Cleaning
of Interior Soft Trim
Dust and loose dirt that accumulate on interior fabric
trim should be removed frequently with a vacuum
cleaner, whisk broom or soft brush. Vinyl or leather trim
should be wiped clean with a damp cloth. Normal
cleanable trim soilage, spots or stains can be cleaned
with the proper use of trim cleaners available through
General Motors dealers or other reputable supply outlets.
Before attempting to remove spots or stains from
upholstery, determine as accurately as possible the
nature and age of the spot or stain. Some spots or stains
can be removed satisfactorily with water or mild soap
solution (refer to accompanying &quot;Removal of Specific
Stains&quot;). For best results, spots or stains should be
removed as soon as possible. Some types of stains or
soilage such as lipsticks, some inks, certain types of
grease, mustard, etc., are extremely difficult and, in some
cases, impossible to completely remove. When cleaning
this type of stain or soilage, care must be taken not to
enlarge the soiled area. It is sometimes more desirable to
have a small stain than an enlarged stain as a result of
careless cleaning.
CAUTION: When cleaning interior soft trim
such as upholstery or carpeting, do not use
volatile cleaning solvents such as: acetone,
lacquer thinners, carbon tetrachloride, enamel
reducers, nail polish removers; or such cleaning
materials as laundry soaps, bleaches or
reducing agents (except as noted in the
instructions on stain removal). Never use
gasoline or naphtha for any cleaning purpose.
These materials may be toxic or flammable, or
may cause damage to interior trim.
Cleaning Fabrics with Cleaning Fluid
This type of cleaner should be used for cleaning stains
containing grease, oil or fats. Excess stain should be
gently scraped off trim with a clean dull knife or scraper.
Use very little cleaner, light pressure, and clean cloths
(preferably cheese cloth). Cleaning action with cloth
should be from outside of stain towards center and
constantly changing to a clean section of cloth. When
stain is cleaned from fabric, immediately wipe area
briskly with a clean absorbent towel or cheese cloth to
help dry area and prevent a cleaning ring. If ring forms,
immediately clean entire area or panel section of the
trim assembly.
NOTE: Sometimes a difficult spot may
require a second application of cleaning fluid
followed immediately by a soft brush to
completely remove the spot.
Cleaning Fabrics with
Detergent Foam Cleaners
This type of cleaner is excellent for cleaning general
soilage from fabrics and for cleaning a panel section
where a minor cleaning ring may be left from spot
1B-25
cleaning. Vacuum area to remove excess loose dirt.
Always clean at least a full trim panel or section of trim.
Mask adjacent trim along stitch or weld lines. Mix
detergent type foam cleaners in strict accordance with
directions on label of container. Use foam only on a
clean sponge or soft bristle brush. Do not wet fabric
excessively or rub harshly with brush. Wipe clean with a
slightly damp absorbent towel or cloth. Immediately
after cleaning fabric, dry fabric, with a dry towel or hair
dryer. Rewipe fabric with dry absorbent towel or cloth to
restore the luster of the trim and to eliminate any dried
residue.
Removal of Specific Stains
Candy
Chocolate, use cloth soaked in lukewarm water; other
than chocolate, use very hot water. Dry. If necessary,
clean lightly with fabric cleaning fluid.
Chewing Gum
Harden gum with ice cube and scrape off with dull knife.
Moisten with fabric cleaning fluid and scrape again.
Fruit Stains, Coffee, Soft Drinks, Ice Cream and Milk
Wipe with cloth soaked in cold water. If necessary clean
lightly with fabric cleaning fluid. Soap and water is not
recommended as it might set the stain.
Catsup
Wipe with cloth soaked in cool water. If further cleaning
is necessary, use a detergent foam cleaner.
Grease, Oil, Butter, Margarine and Crayon
Scrape off excess with dull knife. Use fabric cleaning
fluid.
Paste or Wax Type Shoe Polish
Light application of fabric cleaning fluid.
Tar
Remove excess with dull knife, moisten with fabric
cleaning fluid, scrape again, rub lightly with additional
cleaner.
Blood
Wipe with clean cloth moistened with cold water. Use no
soap.
Urine
Sponge stain with lukewarm soap suds from mild neutral
soap and clean cloth, rinse with cloth soaked in cold
water, saturate cloth with one part household ammonia
water and 5 parts water, apply for 1 minute, rinse with
clean, wet cloth.
Vomitus
Sponge with clean cloth dipped in clean, cold water.
W ash lightly with lukewarm water and mild neutral
soap. If odor persists, treat area with a water-baking
soda solution (1 teaspoon baking soda to one cup of
tepid water). Rub again with cloth and cold water.
Finally, if necessary, clean lightly with fabric cleaning
fluid.
LIGHT DUTY TRUCK SERVICE MANUAL
1B-26 BODY
SEAT MOUNTING
Typical Seat Mounting provisions are shown in figures
73 through 81.
CAUTIO N : See CAUTION on page 1 o f this
section regarding fasteners used on seats and
seat belts.
Fig. 75—Passenger’s Bucket Seat (03)
Fig. 73—Front Bench Seat (03, 06 and 63)
Fig. 74—Driver’s Bucket Seat (03)
Fig. 77—Passenger’s Bucket Seai (14)
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
Fig. 78—Rear Bench Seat (63)
Fig. 80—Rear Folding Seat (06)
Fig. 79—Rear Bench Seat (06)
Fig. 81—Rear Bench Seat (14)
IB -2 7
LIGHT DUTY TRUCK SERVICE MANUAL
1B-28 BODY
BODY MOUNTING
The sequence of mounting attachments is shown in
figures 82 through 85.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-29
Fig. 84—Body Mounting (06)
Fig. 85—Body Mounting (14)
LIGHT DUTY TRUCK SERVICE MANUAL
1B-30 BODY
G MODELS
INDEX
Front End
Windshield Wipers...................................................... ..IB-30
Cowl Ventilator G rille.................................................IB-31
Side Ventilator Valve...................................................IB-31
Rear View M irror....................................................... ..IB-32
Body Glass
Windshield Glass............................................................IB-32
Stationary Glass..............................................................IB-34
Swingout Glass................................................................IB-34
Front Door
Adjustments......................................................................IB-34
Replacement.....................................................................IB-34
W eatherstrip................................................................... ..IB-34
Hinges.................................................................................IB-35
Ventilator..........................................................................IB-36
Window and R egulator...............................................IB-37
Locks, Handles, Rods...................................................IB-37
Sliding Side Door
Front Latch.......................................................................IB-38
Rear Latch........................................................................IB-39
Upper Left H inge..........................................................IB-39
Door Strikers................................................................. ..IB-40
Adjustments.......................................................................IB-40
Rear Door
H inge................................................................................ ..IB-44
Remote Control............................................................. ..IB-44
Latches and R ods..........................................................1B44
Adjustments.......................................................................IB-45
Seats
Drivers Seat......................................................................IB-46
Passenger Seat............................................................... ..IB-47
Rear Seats.........................................................................1B47
FRONT END
WINDSHIELD WIPERS
Windshield wiper units on all models are of the twospeed electric type. A single wiper motor unit, mounted
to dash panel at top and to left of engine cover inside
cab, powers both wiper blades. The wiper blade
operating link rods and pivot mountings on these models
are located in the outside air inlet plenum chamber.
Arm Adjustment
To adjust sweep of blades turn on wipers, then note
sweep of arms. If necessary, remove one or both arms as
follows: Pull outer end of arm away from glass which
will trip lock spring at base of arm and release spring
from undercut of pivot shaft. While holding arm in this
position, pull outward on cap section at base of arm to
remove arm. Arm can be reinstalled in any one of
several positions due to serrations on pivot shaft and in
arm cap. See figure 1G.
attach link rod to motor drive. Disengage link rods
from pins.
4. Remove screws which attach each arm transmission
pivot shaft assembly to cowl. Remove pivot shaft
assembly with link rod from plenum chamber.
Installation
1. Place pivot shaft assembly with link rod into
position at cowl bracket. Secure assembly to bracket
with two screws.
2. Attach end of link rod to motor drive and arm.
Secure rod with the two attaching nuts.
WIPER ARM PIVOT SHAFTS AND LINK
ROD—FIG. 2G
Removal
1. Remove windshield wiper arms from pivot shafts.
Procedure for removing arms is explained previ&shy;
ously under &quot;Arm Adjustments.&quot;
2. Remove screws which attach outside air cowl
ventilator grille to cowl. Carefully remove grille
from cowl.
3. At center of cowl, remove two attaching nuts which
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-31
Fig. 2G—Windshield Wiper Linkage
3. Install outside air cowl ventilator grille to top of
cowl.
4. Before installing wiper arms, operate wiper motor
momentarily which should rotate pivot shafts to
park position. Install arms.
COWL SIDE VENT VALVE
Replacement
1. Remove screws retaining valve guide to panel, as
shown in figure 4G.
2. Remove valve assembly by depressing pins at top
and bottom of valve.
3. Reverse the above steps for installation.
COWL VENTILATOR GRILLE
Replacement
1.
2.
3.
4.
Remove windshield wiper blades.
Remove screws retaining grille, figure 3G.
Remove grille and seal.
Reverse above steps to install grille.
Fig. 3G—Cowl Ventilator Grille
LIGHT DUTY TRUCK SERVICE MANUAL
1B-32 BODY
REAR VIEW MIRRORS
Inside Rear View Mirror
Replacement
The inside mirror may be removed by removing screw
retaining mirror to its glass-mounted bracket, and lifting
mirror off bracket.
Outside Rear View Mirrors
Outside rear view mirror installations are shown in
figure 6G. Occasional tightening of mounting and
assembly bolts and screws will sharply decrease
occurence of failure due to door slamming or road shock.
Fig. 5G—Inside Rear View Mirror
Fig. 6G—Outside Rear View Mirrors
BODY GLASS
WARNING:
dling glass.
Always wear gloves when han&shy;
WINDSHIELD GLASS
The windshield is a one-piece type and is retained in the
windshield opening by a moulded rubber weatherstrip.
This weatherstrip is sealed in the windshield opening
and sealed to the windshield glass. See figure 7G.
When replacing a cracked windshield glass, it is very
important that the cause of the glass breakage be
determined and the condition corrected before a new
glass is installed. Otherwise, it is highly possible that a
small obstruction or high spot somewhere around the
windshield opening will continue to crack or break the
newly installed windshield, especially when the strain on
the glass caused by this obstruction is increased by such
conditions as wind pressures, extremes of temperature,
motion of the vehicle, etc.
The procedure for removal of the windshield applies to
the complete windshield assembly and to other
stationary glass, such as in figure 10G.
Removal
NOTE: Refer to figures 14-16 in the &quot;C-K
Models&quot; portion of this section for illustra&shy;
tion of removal technique.
1. Before removing the windshield, mark the location
of the break on the windshield rubber channel and
the body. Protect the paint finish inside of the cab.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
•APPLY
SEALER
Fig. 7G—Windshield Glass
Mask around the windshield opening and outside,
lay a suitable covering across the hood and fenders.
NOTE: The windshield glass rubber weather&shy;
strip is one piece. The glass is held in a
channel within the weatherstrip.
2. Do not try to remove reveal moldings while
windshield is in body opening. Remove reveal
molding from custom weatherstrip retention groove
after windshield is removed from body opening.
3. To free windshield rubber channel of weatherstrip
loosen the lip of the windshield weatherstrip from
the pinchweld flange along the top and at the sides
by applying firm, controlled pressure to the edge of
the glass. At the same time assist the lip of the
rubber weatherstrip channel over the pinchweld
flange with a flat bladed tool.
IB -3 3
3. Check flange area for solder, weld high spots, or
hardened spot-weld sealer. Remove all high spots.
4. Check windshield glass to opening, by supporting
glass with six spacers contained in packet J-22577,
as shown in figure 8G.
CAUTION: Do not strike glass against body
metal. Chipped edges on the glass can lead to
future breaks.
NOTE: It is necessary to modify the spacers
by cutting off 3/16&quot; from the back of the
spacer with a knife, as shown in figure 8G.
5. With the windshield supported and centered in its
opening, check the relationship of the glass to the
body opening flange around the entire perimeter of
the glass.
6. Check the relationship of glass to opening as
follows:
a. Inside edge of glass to body flange.
b. Outer edge of glass to parallel body metal.
7. Mark areas of body metal or flange to be reformed,
remove glass and correct as necessary.
8. Recheck windshield in its opening and if satisfac&shy;
tory proceed as follows:
Installation
1. Apply sealer to weatherstrip and install on glass.
2. Install a cord around periphery of weatherstrip,
leaving a loop at the top and the loose ends at the
bottom. See figure 9G.
3. Place protective covering over plenum grille, front
fenders and hood.
4. Place windshield and weatherstrip assembly in
opening. With one technician lightly pushing in on
windshield, another technician within the cab
should pull on the cord as follows:
CHECKING BLOCKS
Checking Windshield Opening
Due to the expanse and contour of the windshield it is
imperative in the event of a stress crack that the
windshield opening be thoroughly checked before
installing a replacement windshield. The replacement
glass is used as a template.
1. Check for the following conditions at the previously
marked point of fracture.
a. Chipped edges on glass.
b. Irregularities in body opening.
c. Irregularities in rubber channel weatherstrip.
2. Remove all sealer from flange and body around
windshield opening.
Fig. 8G—Checking Windshield Opening
LIGHT DUTY TRUCK SERVICE MANUAL
1 B -34 BODY
Fig. 11G—Swingout Window
d. Seal windshield to weatherstrip and weatherstrip
to body.
SWINGOUT WINDOW
Removal
1. Swing out the window. See figure 11G.
2. Remove screws retaining latch to body.
3. Remove window hinge retaining screws and
window.
4. Remove latch from glass.
Installation
a. Pull on loose ends until each is within 2&quot; of its
respective upper corner.
b. Pull on loop until cord is within 2&quot; of the upper
corners.
c. Finish seating corners by simultaneously pulling
on both ends of the cord at each corner. This
will insure proper positioning of the critical
upper corners.
1. Install latch to glass using escutcheon, spacer,
washer, latch and screw. Torque to specifications.
2. Place window into opening and install hinge
retaining screws and window.
3. Install latch to glass.
LATCH SWINGOUT WINDOW
Replacement
1. Swing out the window.
2. Remove latch to body and latch to window screws
and remove latch.
3. Reverse above steps for installation.
FRONT D O O R
DOOR ADJUSTMENTS
Doors can be adjusted for alignment of clearance in the
cab door opening, and for proper latching. Door
alignment adjustments are made at the striker bolt, and
at door hinges. The door, when properly located in door
opening, will have equal clearance around its perimeter.
The door should be adjusted in the opening so the edge
of the door across the top and also at the lock side is
parallel with the body opening as nearly as possible.
Hinge Adjustment
Door hinge bolt holes are oversized to make adjustment
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-35
possible. Alignment adjustments can be made by
loosening the proper hinge bolts, aligning door to proper
position, and tightening bolts securely. See figure 12G,
for typical adjustments.
Striker Bolt Adjustment
W ith the use of J-23457, shown in figure 13G, the striker
bolt can be adjusted in any of three ways. See figure
14G.
1. Up and down—To adjust striker up or down, loosen
bolt, adjust to desired height, and tighten bolt
securely.
NOTE: This adjustment is important to
assure that the right proportion of door’s
weight will rest on striker bolt when door is
closed. If bolt is positioned too high on pillar,
rapid wear will occur to the lock cam; if too
low, an extra load will be placed on door
hinges as well as pull door downward and out
of alignment.
2. In and Out—To adjust striker in and out, loosen
bolt, adjust horizontally to desired position and
tighten bolt securely.
3. Forward and Rearward—To make this adjustment,
loosen striker bolt, shim to desired position, and
tighten bolt securely.
Fig. 13G—Loosening Striker Bolt
DOOR HINGE
Remove
1. Remove hinge access hole cover from door hinge
pillar.
2. If removing one hinge, support door in such a
m anner that weight is taken off other hinge, and
that the door will not move.
3. Remove hinge screws from both body and from
door and remove hinge. See figure 12G.
Installation
1.
2.
3.
4.
5.
Install hinge to door and body. Snug bolts.
Remove door supports.
Adjust door as outlined under &quot;Door Adjustment&quot;.
Torque bolts to specifications.
Install hinge access hole covers.
DOOR WEATHERSTRIP
Success of weatherstrip replacement depends entirely
upon the quality of the cement used and the care with
which it is applied. All rust, road dirt and grease or oil
must be completely removed as should all old cement
and bits of old weatherstrip. After removing all foreign
material from door opening surface, wipe down with
prepsol or its equivalent. Use only a good quality cement
which is made specially for weatherstrip installation,
following the m anufacturer’s directions. Proceed as
follows:
LIGHT DUTY TRUCK SERVICE MANUAL
1B 3 6 BODY
1. Open door and block open.
2. Remove side door weatherstrip.
3. Remove used adhesive from door with adhesive or
cement remover.
4. Apply adhesive to door.
5. Install weatherstrip.
6. Trim weatherstrip with a notch, and butt ends
together.
TRIM PANEL, ARM REST AND HANDLES
Removal
1. Remove screws retaining arm rest to trim panel.
2. Remove door handles with Tool J-7797 and pull
from shaft.
3. Remove trim panel screws and remove panel. If
seal is damaged, replace seal.
Installation
1. Install trim panel.
2. Install arm rest. Install door handle washers and
handles.
DOOR VENTILATOR ASSEMBLY
Removal
1.
2.
3.
4.
5.
6.
7.
NOTE: The channel between the door
window glass and door vent is removed as
part of the vent assembly.
Regulate the door window glass to the full down
position.
Remove door handles with Tool J-7797.
Remove trim panel.
Remove rear window run channel screws.
Slide door window glass rearward away from
ventilator.
Remove three screws at the upper front of the door,
as shown in figure 15G.
Turn the vent assembly 90&deg; and carefully remove by
guiding up and out, as shown in figure 16G.
Ventilator Glass Replacement
1. Using an oil can or similar means, squirt prepsol on
the glass filler all around the glass channel or frame
to soften the old seal. When the seal has softened,
remove the glass from the channel.
2. Thoroughly clean the inside of the glass channel
with sandpaper, removing all rust, etc.
3. Using new glass channel filler, cut the piece to be
installed two inches longer than necessary for the
channel. Place this piece of filler (soapstoned side
of filler away from glass) evenly over the edge of
the glass which will fit in the channel. The extra
filler extending beyond the rear edge of the glass
Fig. 16G—Removing Ventilator
should be pinched together to hold it in place
during glass installation.
NOTE: One side of this filler (the outside of
the roll) is soapstoned. This is the side which
goes into the metal channel.
4. Brush the inside of the metal glass channel freely
with ordinary engine oil. This will enable the glass
and filler to slide freely into the channel.
NOTE: Glass should be installed so that rear
edge is parallel to the division post. Allow
full cure before water testing.
Installation
NOTE: Replace the door window glass and
regulate to the full down position before
installing the door ventilator assembly.
1. Lower the ventilator assembly into the door frame.
Center into position.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-37
2. Make certain the rubber lip is positioned before
tightening screws.
3. Slide door glass forward engaging glass in vent
channel.
4. Reinstall all screws and tighten.
5. Install and tighten the three screws at the upper
front of the door.
Adjustment
1. Adjust the ventilator adjusting nut by turning
clockwise to increase operating tension, as shown in
figure 17G.
2. After making adjustment bend tabs over the hex
nut.
3. Install trim panel.
4. Install door and window regulator handles.
DOOR WINDOW ASSEMBLY
Replacement
1. Completely lower glass to bottom of door.
2. Remove inside door and window regulator handles
using Tool J-7797.
3. Remove door arm rest and trim pad.
4. Mask or cover upper portion of door window
frame. Remove ventilator assembly as previously
outlined.
5. Slide glass forward until front roller is in line with
notch in sash channel. Disengage roller from
channel. See figure 18G.
6. Push window forward and tilt front portion of
window up until rear roller is disengaged.
7. Put window assembly in normal position (level) and
raise straight up and out.
8. Reverse above procedure for installation.
Fig. 18G—Window and Regulator
WINDOW REGULATOR
Replacement
1.
2.
3.
4.
5.
Wind window all the way up.
Remove inside door handles with Tool J-7797.
Remove door trim pad.
Remove screws securing regulator to inner panel.
Push regulator out of door opening while holding
rear of assembly, then slide assembly to the notches
in the carrier channel and out through the door
access hole.
6. Install regulator in reverse order of removal,
lubricate regulator gears with lubriplate or
equivalent.
DOOR LOCK—FIGURE 19G
Removal
1.
2.
3.
4.
5.
Raise window.
Remove inside handles with Tool J-7797.
Remove trim panel.
Remove remote control sill knob.
From outside the door remove screws retaining lock
to door edge and lower the lock assembly.
6. Remove screws retaining remote control.
7. Remove screws securing glass run guide channel.
8. Remove lock, push button rod and remote control
rod as an assembly.
Installation
Fig. 17G—Adjusting Ventilator Tension
1. Transfer remote rod with clip to new lock.
2. Connect remote door handle rod to lock after lock
is positioned.
3. Secure lock screws.
4. Secure remote handle.
LIGHT DUTY TRUCK SERVICE MANUAL
1B-38 BODY
5. Check all controls for proper operation before
reinstalling trim and handles.
6. Install remote control sill knob.
NOTE: Connecting rod can be removed at
this point by disconnecting spring clip from
lock.
4. To install, reverse removal procedure.
REMOTE CONTROL AND CONNECTING
ROD—FIG. 19G
LOCK CYLINDER ASSEMBLY—FIG. 20G
Replacement
Replacement
1. Raise door window and remove door trim pad.
2. Remove bolts securing remote control to door inner
panel.
3. Pivot remote inboard slightly, to disengage
connecting rod, and remove remote control from
door.
SLIDING
FRONT LATCH ASSEMBLY
Removal
1.
2.
3.
4.
Remove trim panel (if so equipped).
Remove access cover.
Unscrew door lock knob from rod.
Disconnect the following rods from latch. See figure
21G.
a. Rear latch rods.
b. Lock cylinder rod.
c. Door lock rod.
5. Remove door handle.
6. Remove screws retaining latch assembly to door.
7. Slide latch rearward and lift front of latch.
Disconnect rod leading to lower hinge door catch
1. Raise door window and remove door trim pad.
2. With a screwdriver, or other suitable tool, slide lock
cylinder retaining clip (on door outer panel) out of
engagement and remove lock cylinder.
3. To install, reverse removal procedure.
)E D O O R
by pushing rod out of hole and rotating rod clear of
latch. See figure 22G.
8. Remove latch assembly from door.
Installation
1. Install latch assembly into door by working latch
assembly behind the lower hinge door catch.
2. Connect lower hinge door catch, lock cylinder rod,
door lock rod, and both rear latch rods.
3. Install latch assembly-to-door attaching screws.
Torque to specifications.
4. Install door lock knob and door handle.
5. Install access cover and trim panel.
6. Adjust door front striker as outlined under &quot;Door
Adjustments&quot;.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
Fig. 21G—Sliding Door Front Latch
REAR LATCH AND/OR LATCH ACTUATING
RODS
Removal
1. Remove trim panel (if so equipped).
2. Remove front latch assembly access cover.
3. Disconnect rear latch rods from front latch
assembly. See figure 2lG .
4. Remove rear latch attaching screws. See figure 23G.
5. Slide rear latch toward front of door until rod clips
become exposed. Disconnect rod clips and remove
latch from door.
Installation
1. Connect rods to latch and install latch to door.
Torque screws to specifications.
2. Connect rods to front latch assembly.
Fig.
1B-39
23G—S lid in g Door Rear Latch
3. Install access covers and trim panels (if so
equipped).
4. Adjust door rear latch as outlined under &quot;Door
Adjustments&quot;.
UPPER LEFT HINGE
Removal
1. Open the door.
2. Disengage spring from bolt using a spring removal
tool such as a brake spring removal tool.
3. Close door.
4. Remove hinge assembly.
Disassembly—Fig. 24G
1.
2.
3.
4.
5.
6.
Remove rod connecting hinge and roller assembly.
Remove roller.
Remove levers, noting position of the springs.
Remove nylon block.
Remove bushings by tapping out with a drift.
Reverse Steps l-5 to reassemble. Torque all parts to
specifications.
7. When holding hinge assembly as in figure 25G, the
lower latch must engage cam.
Installation
Fig. 22G—Disconnecting Lower Latch Rod from Latch
1. Install hinge assembly to door. Torque bolts to
specifications.
2. Check and adjust latch to striker position as
outlined under &quot;Door Adjustments&quot;.
3. Turn handle and let door pop open.
4. Connect spring using a brake spring removal tool
or a similar tool.
5. Check operation of door hinge.
LIGHT DUTY TRUCK SERVICE MANUAL
1B-40 BODY
1.
2.
3.
4.
5.
6.
7.
Roller
Lockwashers
Nut
Cam
Washer
Bushing
Bushing
8.
9.
10.
11.
12.
13.
14.
Bolt
15. Screw
Plate
16. Guide Block
Upper lines
17. Hinge (Body Half)
Spacer
18. Nut
Spring (Upper Lever) 19. Bushing
Spring (Lower Level) 20. Bushing
Lower Lever
21. Cam
22 . Bushing
23. Hinge (Door Half)
24. Spring
25. Spring retainer
26. Hinge liner
Fig. 24G—Upper Left Hinge Components
DOOR STRIKERS
CAUTION: See CAUTION on page 1 of this
section regarding Door Strikerfasteners.
Rear Lock Striker
Front Latch Striker
1. Remove striker.
2. Install new striker. Adjust as outlined under &quot;Door
Adjustments&quot; Torque to specifications.
Removal
1. Open door.
2. Remove door striker using tool J-23457. See figure
13G.
installation
1. Install door striker using tool J-23457. Torque to
specifications.
2. Adjust striker as outlined under &quot;D oor
Adjustments&quot;.
SLIDING DOOR ADJUSTMENTS
The side door can be adjusted for alignment and/or
clearance in the body opening and for proper latching.
When properly positioned in the body opening, the door
should have equal clearances around its perimeter.
Door adjustments consist of the following: Up and down,
fore and aft, in and out, front and rear strikers, rear
door wedge, upper left hinge striker, and lower catch.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-41
In and Out
Front in and out adjustments, figure 26G, are provided
by means of an adjustable lower roller mounting bracket,
and for the upper front in and out adjustment the upper
bracket is slotted so the roller can be moved in and out.
Rear in and out adjustment is provided by adjusting the
rear lock striker laterally.
Front and Rear Striker
The front striker provides latching for the front of the
door. The rear striker latches the rear of the door as well
as providing in and out adjustment.
Rear Door Wedge
The rear door wedge located below the door lock striker
helps support the door.
Fig. 25G—Checking Assembly of Hinge
Up and Down
Front up and down adjustments are provided by means
of slotted holes in the door. Rear up and down
adjustments are provided by slotted holes in the upper
left hinge. Refer to figure 26G.
Fore and Aft
Fore and aft adjustments are provided by loosening the
upper left hinge striker (body mounted).
ROLLER A N D BRACKET
ASSEMBLY
IN A N D OUT
ADJUSTMENT
FRONT LATCH
STRIKER
UP A N D D O W N
ADJUSTMENT
Upper Left Hinge Striker
This striker provides adjustment for fore and aft
movement. Also, it acts as a stop for the hinge roller
assembly.
Lower Catch
The lower catch, mounted on the lower front roller, holds
the door in the full open position. The catch engages a
striker installed at the rear of the lower roller channel.
Reposition Door &quot;Up&quot; or &quot;Down&quot;
1. Partially open door and loosen front latch striker
on pillar.
2. Remove upper left door hinge cover.
3. Loosen upper left hinge-to-door bolts.
4. Loosen rear lock striker and door wedge.
5. Loosen upper front roller bracket-to-door bolts.
6. Partially close door and align front edge of door up
or down by loosening front lower hinge-to-door
bolts. Torque bolts to specifications.
7. Align rear edge of door up or down and tighten
upper left hinge-to-door bolts. Torque bolts to
specifications.
8. Position upper front roller in center of track and
tighten roller bracket to door. Torque bolts to
specifications. See figure 27G.
9. Adjust front and rear strikers as outlined under
&quot;Front and Rear Striker Adjustment&quot;.
Reposition Door &quot;Fore&quot; or &quot;Aft&quot;
ROLLER A N D BRACKET
ASSEMBLY
Fig. 26G—Sliding Door Front Adjustments
1. Partially open door and remove front latch striker
and rear lock striker.
2. Loosen upper left hinge stop (on body).
3. Move door assembly forward or rearward as
necessary.
4. Reinstall front and rear strikers and adjust as
outlined under &quot;F ront and Rear Striker
Adjustment&quot;.
LIGHT DUTY TRUCK SERVICE MANUAL
1B-42 BODY
5. Adjust upper left hinge stop as outlined under
&quot;U pper Left Hinge Latch and Stop Adjustment&quot;.
Reposition Door &quot;In &quot; or &quot;Out&quot;
1.
2.
3.
4.
5.
6.
7.
8.
Loosen front latch striker.
Loosen upper front roller from its bracket.
Loosen lower front roller bracket to arm bolts.
Adjust front of door in or out and tighten bolts.
Torque to specifications.
Adjust rear of door in or out by adjusting rear lock
striker.
Adjust front upper roller so it travels in the center
of its channel. See figure 27G.
Adjust front and rear strikers as outlined under
&quot;Front and Rear Striker Adjustment&quot;.
Adjust upper left hinge stop as outlined under
&quot;U pper Left Hinge Latch and Stop Adjustment&quot;.
Front and Rear Striker Adjustment
Front Striker
1. Loosen front striker.
2. Visually align latch to striker relationship and
adjust if necessary. See figure 28G.
3. Slide door forward slowly. Guide on door (just
above latch) must fit snugly within rubber lined
opening on striker assembly.
4. Assure that latch catches fully. Add or delete shims
behind striker as necessary.
Rear Striker
NOTE: The rear striker is adjustable
vertically and transversly after loosening with
Tool J-23457. Also, loosen door wedge located
below striker. Fore and aft adjustment is
obtained by adding or deleting washers
between the bolt and body pillar. The striker
must enter the lock freely.
Up and Down (Vertical) Adjustment
1. Loosen striker with Tool J-23457.
2. Center striker vertically to door striker opening.
3. Adjust laterally to match door outer panel and body
side outer surfaces.
4. Adjust door wedge by aligning wedge on door with
its striker on pillar. Centerline of wedge must enter
centerline of striker opening on pillar.
Fore and Aft (Transverse) Adjustment
5. Smear grease or paint on striker.
6. Gently push door in until lock just contacts striker
enough to make an impression in the grease.
7. Open door and measure distance from rear of
striker head to the impression. Distance should be
.20&quot; minimum to .30&quot; maximum. Refer to figure
29G.
8. Adjust striker by adding or deleting washers
between striker and pillar.
9. Torque striker and wedge to specifications.
Upper Left Door Hinge Striker and Latch
Adjustment (On Body)
CAUTION: If door has been removed and is
being reinstalled adjust striker to lower hinge
lever before closing door. Failure to do so may
cause possible lever breakage.
I. Adjust hinge lower lever to striker contact by
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
1B-43
adding or deleting shims between the striker and
body to provide at least .10 inch of lever contact.
Also, striker must be positioned at least .06&quot; above
bottom of striker tang. See figure 30G.
2. Adjust fore and aft (centering door in opening) by
moving striker horizontally.
3. If necessary to shim roller away from guide, shims
are added between the nylon block and hinge and
between roller and hinge. They must be installed in
pairs. For example, if one shim is added behind the
nylon block another must be added behind the
roller. See figure 31G.
Lower Catch Adjustment
1. Loosen screws retaining catch rod bracket to door.
See figure 32G.
2. Adjust catch to striker engagement by sliding
bracket laterally. Catch should fully engage striker.
Fig. 30G—Hinge Lower Lever to Striker Adjustment
Fig. 32G—Adjusting Lower Catch
Fig. 31G—Shimming Hinge Roller
LIGHT DUTY TRUCK SERVICE MANUAL
1 B -44 BODY
REAR DOORS
REAR DOOR HINGE STRAP
REAR DOOR REMOTE CONTROL
Replacement
Removal
1. Remove strap release pin. See figure 33G.
2. Remove screws retaining strap to door.
3. Install strap to door. Torque retaining screws to
specifications.
REAR DOOR HINGE
Removal
1. Open door. Support door so that when hinge screws
are removed door weight will be on support.
2. Remove hinge strap release pin.
3. Remove hinge-to-door bolts and remove door
assembly.
4. Remove hinge-to-body bolts and hinge.
Installation
1. Install grommet into door hinge opening (if
removed).
2. Install hinge into door. Snug bolts.
3. Install grommet into body hinge opening (if
removed).
4. Install hinge into body opening and install bolts.
Snug bolts.
5. Install hinge strap and its retaining pin.
6. Adjust door and torque hinge bolts to specifications.
1. Remove trim panel.
2. Disengage upper and lower latch rods from control
by removing retaining clips. See figure 34G.
3. Remove remote control by removing its retaining
screws.
Installation
1. Install remote control. Torque screws to
specifications.
2. Reinstall upper and lower latch rods to control.
3. Install trim panel.
REAR DOOR UPPER OR LOWER LATCHES
AND/OR LATCH RODS
Removal
1. Remove trim panel.
2. Disengage rod from remote control assembly. See
figure 34G.
3. Remove latch retaining screws and withdraw latch
and control rod.
4. Remove spring clip retaining rod to latch.
Installation
1. Install latch rod to latch.
Fig. 34G—Remote Control and Latch
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
NOTE: When reinstalling the lower latch rod
to control, the short straight section attaches
to the latch.
2. Install latch and rod assembly into door and
connect rod to remote control.
3. Install latch retaining screws and torque to
specifications.
4. Adjust latch to strikers.
REAR DOOR OUTSIDE HANDLE
Removal
1. Remove trim panel.
2. Remove door handle retaining screws, handle and
gaskets. See figure 35G.
Installation
1. Apply grease to remote control where handle
plunger makes contact.
2. Install handle and gaskets. Torque screws to
specifications.
3. Install trim panel.
REAR DOOR LOCK CYLINDER
Removal
1. Remove trim panel.
2. Remove remote control.
3. Remove lock cylinder retainer and lock cylinder.
Installation
1. Install lock cylinder and retainer.
2. Install remote control. Torque
specifications.
3. Install trim panel.
screws
Fig. 35G—Outside Handle and Lock Cylinder
to
1B-45
REAR DOOR GLASS AND WEATHERSTRIP
Removal and installation procedures are the same as for
the stationary body side windows. Refer to those
procedures for rear door glass and weatherstrip
replacement.
REAR DOOR ADJUSTMENTS
1.
2.
3.
4.
NOTE: Door adjustments are provided by
slotted holes, at hinge attachment, in body
and door.
Remove or loosen door strikers and wedges.
Loosen door hinge bolts and adjust door to provide
equal clearances between body and door around
perimeter of door.
Adjust door in and out so that door panel is flush
with body.
Install door strikers and wedges and adjust as
outlined under door striker adjustment.
REAR DOOR STRIKER ADJUSTMENT
CAUTION: See CAUTION on page 1 of this
section regarding Rear Door Strikerfasteners.
1. Adjust striker by adding or deleting shims as
necessary to obtain dimension as shown in figure
36G. This dimension can be checked by applying
grease to the latch and slowly closing door until
striker fully engages latch. Then open door and
measure from grease impression to bottom of latch
slot. Torque to specifications.
2. Adjust door wedge by adding or deleting shims as
necessary so that wedge contacts bumper on door
when door is closed. See figure 37G.
Fig. 36G—Rear Door Strikers and Wedges
LIGHT DUTY TRUCK SERVICE MANUAL
I B - 4 6 BODY
Fig. 37G—Door Wedge Adjustment
SEATS
CAUTION: See CAUTION on page 1 of this
section regarding fasteners used on seats and
seat belts.
DRIVERS SEAT
Seat Adjuster
Installation
1. Install seat riser to floor. Torque bolts to
specifications.
2. Install seat and torque bolts to specifications.
Removal
1. Remove seat by removing bolts securing seat to seat
riser.
2. Remove seat belt from adjuster.
3. Remove adjuster from seat. See figure 38G.
Installation
1. Install seat adjuster to seat. Torque bolts to
specifications.
2. Install seat belt. Torque retaining nut to
specifications.
CAUTION:
weld nut.
Shoulder of bolt must bottom on
3. Install seat onto seat riser, and torque screws to
specifications.
SEAT RISER
Removal
1. Remove seat and adjusters as an assembly by
removing bolts securing seat to riser.
2. Remove bolts securing seat riser to floor.
LIGHT DUTY TRUCK SERVICE MANUAL
BODY
PASSENGER SEAT—MOUNTING
BRACKETS
Removal
1. Remove seat and brackets from seat riser. See
figure 39G.
2. Remove brackets from seat.
Installation
1. Install brackets to seat. Torque to specifications.
2. Install seat to seat riser. Torque to specifications.
SEAT RISER
Removal
1. Remove seat and mounting bracket as an assembly.
2. Remove riser from floor.
1 B-47
installation
1. Attach leg and support assembly to seat. Torque to
specifications.
2. Attach seat belts. Torque bolts to specifications.
CAUTION:
weld nut.
Shoulder of Bolt must bottom on
3. Attach seat to floor. Torque bolts to specifications.
CARE AND CLEANING OF SEATS
Instructions on care and cleaning of interior soft trim
may be found in &quot;C-K M odels-Seats&quot;, earlier in this
section.
Installation
1. Install riser to floor. Torque bolts to specifications.
2. Install seat to riser. Torque bolts to specifications.
BENCH SEATS—FIGS. 40G, 41G
Seat and/or Seat Support
Removal
1. Remove bolts securing seat legs to floor.
2. Remove seat assembly.
NOTE: After removing the rear seat, reinstall
the bolts into the anchor nuts to seal the
openings from dirt and foreign matter.
3. Remove legs and support assembly.
Fig. 40G—Bench Seat 2nd or 3rd Position
Fig. 39G—Passenger Seat
Fig. 41G—Bench Seat 4th Position
LIGHT DUTY TRUCK SERVICE MANUAL
1B-48 BODY
SPECIAL TOOLS
mmmmmr
12.
3.
4.
5.
J-2189
J-22585
J-22577
J-7797
J-23457
Weatherstrip Tool Set
Front Door Hinge, Bolt Wrench
Windshield Checking Blocks
Door Handle Clip Remover
Door Striker Bolt Remover and Installer
Fig. IT —Special Tools
LIGHT DUTY TRUCK SERVICE MANUAL
SECTION 2
FRAME
INDEX
.2-1
.2-1
.2-1
.2-2
.2-2
Description 10-30 Series Truck
M aintenance...................................
Frame Alignment.....................
Horizontal C heck...................
Vertical Check.........................
Frame Repair......................................................................2-2
W elding...............................................................................2-2
Bolting..................................................................................2-2
Underbody A lignm ent.....................................................2-2
DESCRIPTION
Light duty 10-30 Series frames are of the ladder channel
section riveted type.
Figure 1 illustrates typical light duty frames with
crossmembers, body mounts and suspension attaching
brackets. This section also included general instructions
for checking frame alignment and recommendations on
frame repair.
The G-Van frame side rails, cross sills and outriggers are
part of the underbody assembly which is a welded unit.
Misalignment of the underbody can affect door opening
fits and also influence the suspension system, causing
suspension misalignment. It is essential, therefore, that
underbody alignment be exact to within - 1/16&quot; of the
specified dimensions.
M AINTENANCE
UNDERBODY AND FRAME
INSPECTION
UNDERBODY INSPECTION
Raise the vehicle on a hoist (preferably a twin-post type).
Check for obvious floor pan deterioration.
Check for loose dirt and rust around the inside of the
floor pan reinforcement member access holes. This is the
first indication that corrosion may exist in hidden areas,
and that repairs might be required before the final
cleaning and protective treatment is performed.
Using a chisel, ensure that the drain provisions in the
floor pan reinforcement members are open.
There are drain holes in the body side panels also. These
holes can be opened by using a punch or drift. The side
panel drain holes are in the rear section of the rocker
panels, and in the lower rear quarter panels.
must be used for vertical checks, opposite and alternate
sides for horizontal checks.
Vehicle Preparation
Points to remember when preparing vehicle for frame
checking:
1. Place vehicle on a level surface.
2. Inspect damaged areas for obvious frame misalign&shy;
ment to eliminate unnecessary measuring.
3. Support vehicle so that frame sidemembers are
parallel to the ground.
Tramming Sequence
1. Dimensions to bolts and/or holes in frame extend
to dead center of the hole or bolt.
FRAME ALIGNMENT
Horizontal frame checking can be made with tramming
gauges applied directly to the frame or by transferring
selected points of measurement from the frame to the
floor by means of a plum bob and using the floor layout
for measuring. Figure 2 may be used as a general guide
in the selection of checking points; however, selection of
these points is arbitrary depending on accessibility and
convenience. An important point to remember is that for
each point selected on one side of the frame, a
corresponding point on the opposite side of the frame
Fig. 1 - 1 0 - 3 0 Series Frame—Typical
LIGHT DUTY TRUCK SERVICE MANUAL
2-2 FRAME
2. Dimensions must be within 3/16&quot;.
3. If a tram bar is used, for horizontal alignment &quot;X &quot;
- check from opposite and alternate reference
points AA, BB and CC, as illustrated by the lines in
Figure 2. Error will result if a tram bar is not level
and centered at the reference points.
4. Obtain vertical dimensions and compare the
differences between these dimensions with the
dimensions as shown in chart.
Horizontal Check
1. Measure frame width at front and rear. If widths
correspond to specifications, draw centerline full
length of vehicle halfway between lines indicating
front and rear widths. If frame widths are not
correct, layout centerline as shown in Step 4.
2. Measure distance from centerline to corresponding
points on each side of frame layout over entire
length. Opposite side measurement should corre&shy;
spond within 3/16&quot;.
3. Measure diagonals marked A, B and C. If the
lengths of intersecting diagonals are equal and
these diagonals intersect the centerline, frame area
included between these points of measurement may
be considered in alignment.
4. If front or rear end of frame is damaged and width
is no longer within limits, frame centerline may be
drawn through the intersection of any two
previously drawn pairs of equal, intersecting
diagonals.
Vertical Check
Vertical dimensions are checked with a tramming bar
from indicated points on the frame (figs. 3 and 4). For
example, if the tram bar is set at point B with a vertical
pointer length of 8-1/4 inches, and at point E with a
vertical pointer length of 5-1/4 inches (a height
difference of 3 inches), the tram bar should be parallel
with the frame. If the area is twisted or misaligned in
any way, tram bar will not be parallel. Placing the tram
bar vertical pointers on opposite sides of the frame side
rail is preferable in that frame twist will show up during
this vertical check. Figures 3 and 4 show typical checking
points, with dimensions for various frames shown in the
chart below.
Frame Repair
Welding
Before welding up a crack in frame, a hole should be
drilled at the starting point of the crack to prevent
spreading. Widen V groove crack to allow complete weld
penetration.
NOTE: Do not weld into corners of frame or
along edges of side rail flanges. Welding at
these points will tend to weaken the frame
and encourage new cracks.
Bolting
Wherever rivets or failed bolts are replaced, bolt hole
must be as near the O.D. of the bolt as possible to
prevent bolt from working and wearing. Drill out and
line ream hole (or holes) to the bolt O.D.
UNDERBODY ALIGNMENT
One method of determining the alignment of the
underbody is with a tram gauge which should be
sufficiently felxible to obtain all necessary measurements
up to three quarters the length of the vehicle. A good
tramming tool is essential for analyzing and determining
the extent of collision m isalignm ent present in
underbody construction.
MEASURING (Fig. 5)
To measure the distance accurately between any two
reference points on the underbody, two specifications are
required.
1. The horizontal dimension between the two points to
be trammed.
2. The vertical dimension from the datum line to the
points to be trammed.
The tram bar should be on a parallel to that of the body
plane. The exception to this would be when one of the
reference locations is included in the misaligned area;
then the parallel plane between the body and the tram
bar may not prevail. After completion of the repairs, the
tram gauge should be set at the specified dimension to
check the accuracy of the repair operation.
EXCESSIVE BODY DAMAGE
If damage is so extensive that key locations are not
suitable as reference points, repair operations should
always begin with the underbody area. All other
components should be aligned progressively from this
area. Unlike the conventional type of frame design, the
unitized type of body construction seldom develops the
two conditions of &quot;twist&quot; and &quot;diam ond&quot; in the
underbody area as a result of front or rear end collisions,
therefore, there usually is an undam aged area suitable as
a beginning reference point.
LIGHT DUTY TRUCK SERVICE MANUAL
k
LIGHT
DUTY
FRAME
TRUCK
SERVICE
2-3
M ANUAL
Fig. 2- Frame Horizontal Checking - Typical
2 -4 FRAME
Fig 3--KA Frame
Model
A
B
C
D
CA107 9 - 3 /8 1 1 -7 /8 1 3 -3 /8 16
CA109 9 - 3 /8 1 1 -7 /8 1 3 -3 /8 16
CA209 9 - 3 / 8 1 1 -7 /8 1 3 - 3 /8 16
LCA210
310 9 - 3 /8 1 1 -7 /8 1 2 -3 /4 16
CA314 9 - 3 /8 1 1 -7 /8 1 2 -3 /4 16
KA107 9 - 3 /8 1 1 -7 /8 1 3 -1 /8 16
E
F
G
1 0 -1 /4 7 - 1 /8 10
10 -1 /4 7 - 1 /8 10
1 0 -1 /4 7 -1 /8 10
7 -1 /2
10
H
I
J
1 3 - 3 /8 1 5 -1 /2 12
1 3 -3 /8 1 5 -1 /2 12
1 3 -3 /8 15 -1 /2 12
L
M
11 -3 /8 1 3 - 3 /8 43
11 -3 /8 1 3 -3 /8 43
1 1 -3 /8 1 3 -3 /8 43
N
92
104
104
O
P
Q
R
S
1 2 7 -3 /4 14
134
14
134
14
1 6 -7 /8 1 9 -1 /8 1 6 - 7 /8
16 -7 /8 19 -1 /8 1 6 - 7 /8
1 6 -7 /8 1 9 - 1 /8 1 6 - 7 /8
9 0 - 3 /8 1 58-1/4 14
1 6 -7 /8 1 6 -7 /8 1 6 - 7 /8
90
92
1 80-1/2 14
127 -3 /4 14
16 -7 /8 16 -7 /8 1 6 -7 /8
1 6 - 7 /8 1 6 - 7 /8 1 6 -7 /8
104
139 -3 /4 14
1 6 - 7 /8 1 6 -7 /8 1 6 -7 /8
79
114 -5 /8 14
1 6 -7 /8 1 9 -1 /8 1 6 -7 /8
7 -1 /2 6 - 1 /8 10
1 0 - 1 /4 7 - 1 /8 10
1 0 -1 /4 1 3 - 3 /8 49
8 - 3 /8 17 -1 /8 1 4 -1 /4 1 4 -1 /4 1 7 -1 /8 49
1 3 - 3 /8 1 4 -5 /8 12
1 0 -3 /4 1 3 -3 /8 43
KA109
^ 2 0 9 9 - 3 /8 11 -7 /8 1 3 - 1 /8 16
PA100 9 - 3 /8 1 1 -7 /8 1 3 -3 /8 16
1 0 -1 /4 7 - 1 /8 10
1 3 -3 /8 1 5 -1 /2 12
1 0 -3 /4 1 3 -3 /8 43
1 0 -1 /4 7 - 1 /8 10
1 3 -3 /8 1 5-1/2 12
1 0 -3 /4 1 3 -3 /8 43
PA208
308 9 - 3 /8 1 1 -7 /8 1 2 -3 /4 16
1 3 -1 /2 7 -1 /2 10
10
1 5 -1 /8 1 1 -5 /8 1 1 -1 /4 1 3 - 3 /8 3 1 - 5 /8
9 - 3 /8 1 1 -3 /8 1 2 -3 /4 16
1 3 -1 /2 7 -1 /2 10
10
1 5 -1 /8 1 1 -5 /8 1 1 -1 /4 1 3 -3 /8 3 1 - 1 /2 1 07-3/4 183 -3 /4 1 6 - 7 /8 1 6 -7 /8 1 6 -7 /8 1 6 -7 /8
9 -3 /8 1 1 -7 /8 1 2 -3 /4 16
9 - 3 /8 1 1 -7 /8 1 3 - 3 /8 16
9 - 3 /8 1 1 -7 /8 1 3 -1 /8 16
1 3 -1 /2 7 -1 /2 10
1 0 -1 /4 7 - 1 /8 10
1 0 -1 /4 7 - 1 /8 10
10
1 5 -1 /8 1 1 -5 /8 1 1 -1 /4 1 3 -3 /8 3 1 - 1 /2 1 31-3/4 2 0 7 -3 /4 1 6 - 7 /8 1 6 -7 /8 1 6 -7 /8 1 6 -7 /8
1 3 -3 /8 1 5 -1 /2 12
1 3 -3 /8 43
81
14
1 6 -7 /8 1 9 -1 /8 1 6 -7 /8
1 3 -3 /8 1 4 -5 /8 12
1 0 -3 /4 1 3 -3 /8 43
81
116 -3 /4 14
1 6 -7 /8 1 6 -7 /8 1 6 -7 /8
PA210
310
PA314
CA105
KA105
PE
31132 9 -1 /4
137) i
-
10
K
1 5 -1 /8
9 9 - 3 /4 175 -3 /4 1 6 - 7 /8 1 6 -7 /8 1 6 -7 /8 1 6 -7 /8
1 1 -5 /8 12-5/8 15-3/4 1 3 -3 /8 7 - 3 /8
9 -3 /4 9 -3 /4 15
11-1/2 1 1 -1 /8 13-1/8 3 1 - 1 /2 111-3/4 187-3/4 14
1 6 -7/8 1 6-7/8 16-7/8
PE
31432 9 -1 /4 11-5/8 12-5/8 15-3/4 1 3-3/8 7 - 3 /8
(157)
9 -3 /4 9 -3 /4 15
11-1/2 1 1-1/8 1 3 -1 /8 3 1 - 1 /2 131-3/4 2 0 7 -3 /4 14
1 6 -7/8 1 6-7/8 1 6-7/8
A
LIGHT DUTY TRUCK SERVICE MANUAL
LIGHT
DUTY
SERVICE
FRAME
TRUCK
2-5
M ANUAL
Fig. 4-10-30 Series Truck Frame
Fig. 5--Underbody
Reference Points • G-Van
2-6 FRAME
LIGHT DUTY TRUCK SERVICE MANUAL
SECTION 3
FRONT SUSPENSION
The following caution applies to one or more steps in the assembly
procedure of components in this portion of the manual as indicated at
appropriate locations by the terminology “See Caution on page 1 of this
Section” .
CAUTION THIS FASTENER IS A N IMPORTANT A TTACHING PART
IN THAT IT COULD AFFECT THE P E R F OR MA NC E OF VITAL
COMPONENTS A N D SYSTEMS, AND/OR CO ULD RESULT IN
MAJOR REPAIR EXPENSE. IT M U S T BE REPLACED WITH ONE
OF THE SA ME PART N U M B E R OF WITH A N EQUIVALENT PART
IF REPLAC EM EN T B EC O M E S NECESSARY. D O N O T USE A
REP LA CE ME NT PART OF LESSER QUALITY OR SUBSTITUTE
DESIGN. TORQUE VALUES M U S T BE USED AS SPECIFIED
DURING REASSEMBLY TO ASSURE PROPER RETENTION OF
THIS PART.
CONTENTS OF THIS SECTION
Front Suspension - 2 Wheel Drive........................................................ 3-2
Front Suspension - 4 Wheel Drive........................................................ 3-38
INDEX
General Description................................................................
Theory of Operation.............................................................
K-Series Suspension.............................................................
Independent Suspension......................................................
Steering Knuckle and Wheel Spindle..............................
Control Arms.....................................................................
Ball Joints...........................................................................
Coil Springs.........................................................................
Leaf Springs........................................................................
Shock Absorbers................................................................
Wheel Alignment....................................................................
Front Suspension Geometry...............................................
Caster..................................................................................
Camber................................................................................
Toe-In..................................................................................
Toe-Out on Turns...............................................................
Steering Axis Inclination..................................................
Preliminary Adjustments..................................................
Maintenance and Adjustments..............................................
Wheel Bearing—Check Adjustment....................................
Front Alignment Description.............................................
Camber.................................................................................
Caster...................................................................................
How to Determine Caster.................................................
Tow-In................................................................................
Definitions..........................................................................
3-2
34
3-4
34
3-5
3-5
3-5
3-5
3-5
3-5
3-9
3-9
3-9
3-10
3-10
3-10
3-10
3-10
3-12
3-12
3-12
3-13
3-13
3-13
3-14
3-14
Component Parts Replacement............................................
Wheel Hubs and Bearings.....................................................
Removal..............................................................................
Inspection...........................................................................
Repairs.................................................................................
Bearing Cups—Replace....................................................
Wheel Stud Replacement................................................
Installation............. ............................................................
Shock Absorbers..................................................................
Removal...............................................................................
Installation..........................................................................
Stabilizer Bar.........................................................................
Coil Spring............................................................................
Leaf Spring - K Series..........................................................
Upper Control Arm Pivot Shaft
and Bushings (Steel)........................................................
Lower Control Arm Pivot Shaft
and Bushings (Steel)........................................................
Upper Control Arm Assembly............................................
Rubber Bushings................................................................
Lower Control Arm Assembly............................................
Rubber Bushings................................................................
Ball Joint Service..................................................................
Inspection...........................................................................
Replacement......................................................................
3-16
3-16
3-16
3-16
3-17
3-17
3-17
3-17
3-17
3-17
3-17
3-17
3-18
3-19
3-19
3-20
3-21
3-21
3-22
3-22
3-22
3-23
3-24
LIGHT DUTY TRUCK SERVICE MANUAL
3-2 FRONT SU S PEN SIO N
Steering Knuckle/Steering Arm......................................... .3-25
Removal...............................................................................3-26
Installation...........................................................................3-26
Crossmember and Suspension Unit.....................................3-26
Removal...............................................................................3-26
Installation...........................................................................3-26
Diagnosis................................................................................. .3-27
Front Suspension..................................................................3-27
Ball Joint............................................................................... .3-30
Shock Absorber.................................................................... .3-31
On Vehicle...........................................................................3-31
Bench....................................................................................3-32
Bearings and Races................................................................3-33
Special Tools............................................................................3-37
GENERAL DESCRIPTION
The GM 10-30 series Truck line except K Series
incorporates an independent coil spring front suspension
system. (Figs. 1 and 2).
The control arms are of unequal length (S.L.A. Type)
and is used on all 10, 20 and 30 series vehicles without 4
wheel drive.
This suspension system consists of upper and lower
control arms pivoting on steel threaded or rubber
bushings on upper and lower control arm shafts. The
lower control arms are attached to the crossmember with
U-bolts. The upper control arms are attached to a frame
bracket. These control arms are connected to the steering
knuckle through pivoting ball joints.
A coil spring is located between the lower control arm
and a formed seat in the suspension crossmember, thus
the lower control arm is the load carrying member.
Double acting shock absorbers are also attached to the
lower control arms and connect with the frame to the
rear on the upper end. The front wheel bearings are
tapered roller type and are used on all models.
Fig. 1—Front Suspension - G-30—Typical
LIGHT DUTY TRUCK SERVICE MANUAL
DUTY
C 10
TRUCK
P 10-30
FRONT SUSPENSION
LIGHT
G 10-20
MANUAL
3-3
SERVICE
Fig. 2—Front Suspension C -P-K Typical
3-4 FRONT SU SPEN SION
Fig. 3—Wheel Hubs and Bearings
THEORY OF OPERATION
The front suspension can be divided into two types, the
CONVENTIONAL, such as used on General Motors K Series
trucks, or the INDEPENDENT, such as used on all other
General Motors light duty trucks.
The description of caster, camber, toe-in, toe-out — on
turns and steering axis or kingpin inclination is the same
for conventional or independent types of suspensions.
The description of the control arms and related parts as
well as adjustment methods is intended for the
independent front suspension only.
K-SERIES SUSPENSION
The K-Series suspension system, as described here, refers to
leaf springs and a tubular axle. The tubular axle attached to
the vehicle through the leaf springs that are secured to the
axle on a spring pad. The spring ends, called eyes, are
attached to the vehicle frame through hangers.
The steering knuckle and wheel spindle attach to the axle
ends through ball joints. Caster can not be changed on
this particular vehicle and is designed and built into the
suspension. The camber setting is built into the axle and
cannot be changed. Toe-in is changed in a manner
similar to all other G.M. vehicles.
INDEPENDENT SUSPENSION
The independent suspension system, as described here,
refers to coil springs and control arms. Control arms and
coil springs are covered later in this section.
The term “independent suspension” describes a method
of supporting the chassis on the wheels without the use
of rigid axles. When a pair of wheels are mounted to a
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT S U S PEN SIO N
rigid axle and one of them passes over a bump the axle
executes an angular movement in the (front view)
vertical plane and both of the wheels perform
movements of the same angular magnitude. With
independent suspension the movement of the two wheels
are not interdependent; one wheel does not force the
other wheel to deflect.
W ith the independent suspension, the steering knuckle
and wheel spindle are connected to the vehicle through
ball joints and control arms.
Steering Knuckle and Wheel Spindle
The wheel spindle is the unit that carries the hub and
bearing assembly with the aid of the knuckle assembly.
The hub assembly has also become the brake disc
assembly.
As pointed out under conventional and independent
suspensions, the wheel spindle is connected to the vehicle
through a steering knuckle and ball joints.
The spindle carries the entire wheel load. In order to
reduce friction, on the sprindle and wheel hub, wheel
bearings are provided. The design and placement of
these bearings on the spindle is such that the center
plane of the wheel is closer to the center plane of the
wheel is closer to the center plane of the inner bearing
than the outer bearing. The reason for this is to bring
the wheel as close as possible to the knuckle axis. For this
same reason the inner bearing will usually be larger than
the outer bearing. Wheel bearing service is covered in
detail elsewhere in this section.
Coil Spring
Coil springs are just what their name implies. They are
coils of steel wire. A coil spring can be installed on the
front suspension or rear suspension of a vehicle with the
method of attachment varying to suit the application.
On the front suspension the lower control arm provides
the seat for the coil spring with the upper end housed
within the frame crossmember. The function of the coil
spring is the same as the leaf spring, that is, to cushion
shock imparted to the wheel by road roughness or
obstacles.
Since a coil spring provides little directional stability
control arms are provided and connect between the
vehicles frame and axle assembly.
Shock absorbers are used with the springs and are
covered elsewhere in this section.
3-5
bolted to the steering knuckle. This arrangement allows
the front wheel suspension to move up and down with
respect to the vehicle frame (spring action) and swing at
various angles for vehicle steering.
Control Arm Bushings
Two different types of bushings are used in 1973
independent suspension trucks. G-10 and 20 series and
C-10 series trucks use new rubber bushings for both
upper and lower control arms. All P series, C-20/30 and
G-30 use steel bushed upper and lower control arms. The
rubber bushings provide a better more enjoyable ride,
while the steel bushings are needed for heavy duty
applications.
BALL JOINTS (Fig. 5)
Ball joints are used to connect the control arms to the
steering knuckle. The upper ball joint is usually riveted
to the control arm and connects to the steering knuckle
through a tapered stud that is held in position with a
castellated nut and a cotter pin. The lower ball joint is
usually pressed into the control arm and connects to the
steering knuckle through a tapered stud that is held in
position with a castellated nut and a cotter pin.
A ball joint stud, nut and rubber seal is about all your
eye will see of the ball joint assembly. The function of
the rubber seal is to retain the lubricating grease, which
it contains, and to protect this grease from contam ina&shy;
tion by water or foreign material (sand, dirt, etc.). If this
seal is damaged (torn or pulled off its metal retainer) the
ball joint should be replaced. Check the Service
procedure for inspection and replacement of a ball joint
suspected of being in need of replacement.
NOTE: Grease fittings on ball joints should
be wiped clean before applying grease to the
joint.
SHOCK ABSORBERS
Shock absorbers are hydraulic devices that help to
control the up-and-down and rolling motion of a vehicle
SHORT ARM
BALL JOINT
CONTROL ARMS
(Independent Suspension)
The front control arms are said to be the SLA type
(Short and Long Arm). The control arms attach to the
vehicle with bolts at their inner pivot points and to the
steering knuckle (which is part of the front wheel
spindle) at their outer points. The outer attachment is
made through ball joints secured to the control arms and
Fig. 4—Control Arms
LIGHT DUTY TRUCK SERVICE MANUAL
3-6 FRONT SU SPEN SION
BALL JOINT ASSEMBLY
UPPER MOUNT
SEAL COVER
SEAL
SEAL SPRING
ROD GUIDE
CYLINDER TUBE
REBOUND SPRING
PISTON NUT
CYLINDER END
BASE CUP
Fig. 5—Ball Joints-Typical
body while at the same time controlling wheel and axle
motions.
The vehicle’s springs support the body, but shock
absorbers work with the springs to control movements of
the body, wheel, and axle for smooth driving. This is
accomplished by changing the movements of the spring
(kinetic energy) into heat energy. Therefore, a shock
absorber may be considered as a damper to control the
energy stored up by the springs under load.
COMPRESSION
VALVE CAGE
LOWER MOUNT
RELIEF VALVE
Fig. 6—Major Components of a Shock Absorber
C O M PR ES S IO N FORC E
t
Operation
A shock absorber is sometimes compared to a water
pistol. Of course, there are many steps between a water
pistol and a shock absorber, but both are damping
devices and both use the same principle—they force an
incompressible liquid through small openings.
There are usually four shock absorbers on a vehicle; one
located near each wheel. They are direct-acting because
of their direct connection between the vehicle frame
(body) and the axle (or wheel mounting member). They
are also double-acting because they control motion in
both directions of the suspension travel. Up movements
of the body are termed rebound and down movements,
compression.
The compression movement of the shock absorber causes
the piston to move downward with respect to the cylinder
tube (figure 7), transferring fluid from chamber B to
chamber A. This is accomplished by fluid moving
through the outer piston holes and unseating the piston
intake valve. Since all the fluid in chamber B cannot pass
into chamber A due to the volume of the piston rod, the
fluid equivalent to the rod volume is discharged out of
the compression valve into chamber C of the reservoir
with a corresponding compression of the air in chamber
D. Compression control is the combination of load due
to the compression valve and of load due to the piston
intake valve.
The rapid movement of the fluid between the chambers
during the rebound and compression strokes can cause
FLUID
(H YD R A U LIC )
A IR OR
GAS FILLED
CELL
PISTON
IN TA K E
V A LV E
B LO W -O FF
V A LV E
PISTON H OLES
FLU ID
(H YD R A U LIC )
HIGH VELO C ITY
ORIFICE
LO W V ELO C ITY
ORIFICE
BLOW O FF
VA LV E
B LOW O FF PORT
Fig. 7—Shock Absorber Compression Schematic
aeration or foaming of the fluid (aeration is the mixing
of free air and the shock fluid). W hen aeration occurs,
the shock develops lag (piston moving through an air
pocket which offers no resistance). Two means of
eliminating aeration are utilized. One is a spiral groove
reservoir tube, Figure 8, which breaks up the air bubbles
in the fluid. The other is a gas filled cell, Figure 9, which
replaces the free air in a shock absorber.
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT S U S P E N S IO N
This cell, in the reservoir, acts the same as an air
chamber, expanding and contracting to compensate for
the volume of the piston rod. But since it is a gas filled
cell, there is no free air to mix with the fluid; thus,
aeration is eliminated.
A rebound or extension stroke, Figure 10, will cause the
pressure in chamber B to fall below that in chamber C.
As a result, the compression valve will unseat and allow
fluid to flow from chamber C into chamber B. Chamber
D contains air which expands to compensate for the
piston rod volume being removed. Simultaneously, fluid
in chamber A will be transferred into chamber B
through the inner piston holes and the rebound valve.
Rebound control is determined by the piston rebound
varying.
Sometimes shock absorbers are used to limit the rebound
travel of a suspension system. This type of usage is
prim arily for front suspension systems and permits the
rubber rebound bump stop to be omitted. Shock
absorbers used in this manner have a different type of
internal construction which controls the rebound stroke.
This construction is called &quot;rebound cut-off&quot;. On the
rebound stroke, all fluid passing from chamber A to
chamber B, see Figure 10, through the piston valving
parts must first flow through the piston rod. The fluid
flows through the piston rod by means of intersecting
holes, one along the axis of the piston rod and the other
perpendicular to it. As the shock absorber approaches
the end of the rebound stroke, the passage in the piston
rod enters the rod guide, gradually restricting the flow of
the fluid. As the flow is restricted, the control of the
shock absorber increases. W hen the passage is
completely closed off the by rod guide, see Figure 11, a
small amount of fluid is trapped in chamber A creating a
hydraulic stop which limits the full rebound travel of the
suspension system.
As the piston moves, forcing fluid through calibrated
orifices, pressure increases within the cylinder. This
pressure acting against the effective area of the piston
determines the resistance or control provided by the
shock absorber. Low piston velocities create low
pressures, whereas high piston velocities with the same
orifice result in considerably higher pressures. For
3-7
Fig. 9—Gas Filled Cell Shock Absorber
EXTEN SIO N FORCE
CYLINDER
TUBE
Fig. 10—Shock Absorber Rebound Schematic
SPIR A L-G R O O VE
RESERVOIR
Fig. 8—Spiral-Groove Shock Absorber
example, body lean during a turn will result in low force
in the shock absorber due to low piston velocity; while
hitting a chuckhole at high speeds will generate high
resistance forces.
The system of valves and orifices in a shock absorber
which is referred to as the “valving,” is composed of
three .distinct stages, which generate rebound and
compression resistance levels (control) dependent upon
LIGHT DUTY TRUCK SERVICE MANUAL
3-8 FRONT SU SPEN SION
EXTEN SIO N FORCE
INTAKE VALVE
SPRING
COMPRESSION
VALVE ASSY.
HIGH SPEED
ORIFICE
■*--------- VALVE CAGE
VALVE STEM
RESERVOIR
BLOW OFF
VALVE
SPRING
COM PRESSION
LOW SPEED
ORIFICE
RETAINER
WASHER
CYLINDER END
Fig. 11—Shock Absorber Rebound Cut Off Schematic
Fig. 12—Compression Valve Parts
shock absorber piston velocity. Figure 13 illustrates
rebound valving, and Figure 12 illustrates compression
valving. The three stages are described as follows.
blow-off valve opens as soon as the pressure is great
enough to unseat the valve, after which the low speed
orifice ceases to have an appreciable effect. As the
pressure of the fluid against the spring increases, the
valve continues to open until it reaches its maximum lift.
Low Speed Orifice (First Stage)
Two low speed orifices control fluid passage during slow
body or wheel motions. The low speed orifice for
rebound consists of slots in the orifice disc of the
rebound valve, Figure 13, whereas the low speed orifice
for compression consists of depressions in the cylinder
end of the compression valve, Figure 12. This stage has
its major effect in controlling low speed body
movements. A very small, low speed orifice will cause a
harsh ride in which every bump will be felt, similar to
driving with over-inflated tires.
Blow-Off Valve (Second Stage)
Two blow-off valves, Figures 12 and 13, control the fluid
motion during intermediate body and/or wheel motion.
Depending on direction of stroke, the spring-loaded
High Speed Orifice (Third Stage)
After the blow-off valve is completely open, further
increases in control at even higher piston velocities is
caused by restriction due to the high speed orifice.
Basically, there are two high speed orifices. The high
speed orifice on the rebound stroke is the holes in the
inner ring of the piston, Fig. 14. The high speed orifice
on the compression stroke is the hole in the compression
valve cage, Figure 12, in combination with the slots in
the outer ring of the piston. The high speed orifices are
large enough not to affect flow through the low speed
orifices or during the opening of the blow-off-valves, but
will quickly increase the control under conditions such as
wheel-hop, where high piston velocities are present.
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
COMPRESSION
SIDE
3-9
BACK WASHER
INTAKE SPRING
INTAKE VALVE DISC
PISTON-HIGH SPEED ORIFICE
TYPICAL REBOUND ORIFICE DISC
REBOUND SPRING DISC
REBOUND
SIDE
SPACING SPRING DISC
LO W SPEED
ORIFICE
SPRING SEAT
REBOUND SPRING
PISTON ASSEMBLY
PISTON NUT &quot; ► i
— BLOW-OFF
VALVE
Fig. 13—Piston Valving Parts
Fig. 14—High Speed Orifices in Piston
WHEEL ALIG NM ENT
FRONT SUSPENSION
GEOMETRY (FIG. 15)
The term “front suspension geometry” refers to the
angular relationships between the front wheels, the front
suspension attaching parts and the ground. The angle of
the knuckle (or steering axis inclination) away from the
veritcal, the pointing in or “toe-in” of the front wheels,
the tilt of the front wheels from vertical (when viewed
from the front of the vehicle) and the tilt of the
suspension members from vertical (when viewed from
the side of the vehicle), - all these are involved in front
suspension geometry. The various factors that enter into
front-end geometry are covered here each one under its
own heading.
CASTER
Caster is the tilting of the front steering axis either
forward or backward from the vertical (when reviewed
from the side of the vehicle). A backward tilt is said to
be positive(-F) and a forward tilt is said to be negative
(—). On the short and long arm type suspension you
cannot see a caster angle without a special instrument,
but you can understand that if you look straight down
from the top of the upper control arm to the ground you
would find that the ball joints do not line up (fore and
aft) when a caster angle other than 0&deg; is present. If you
had a positive caster angle the lower ball joint would be
slightly ahead (toward the front of the vehicle) of the
upper ball joint center line. In short then: caster is the
forward or backward tilt of the steering axis as viewed
from a side elevation. Caster is designed into the front
axle assembly on all K series vehicles and is nonadjustable. See caster copy under ADJUSTMENTS.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -1 0 FRONT SUSPENSION
CAMBER
Camber is the tilting of the front wheels from the
vertical when viewed from the front of the vehicle.
When the wheels tilt outward at the top, the camber is
said to be positive ( + ). When the wheels tilt inward at
the top, the camber is said to be negative (—). The
amount of tilt is measured in degrees from the vertical
and this measurement is called the camber angle.
Camber is designed into the front axle assembly of all K
series vehicles and is non-adjustable. See camber copy
under ADJUSTMENTS.
TOE-IN
Toe-in is the turning in of the front wheels. The actual
amount of toe-in is normally only a fraction of an inch.
The purpose of a toe specification is to ensure parallel
rolling of the front wheels. (Excessive toe-in or toe-out
will cause tire wear) Toe-in also serves to offset the small
deflections of the wheel support system which occurs
when the vehicle is rolling forward. In other words, even
when the wheels are set to toe-in slightly when the
vehicle is standing still, they tend to roll parallel on the
road when the vehicle is moving. See toe-in copy under
ADJUSTMENTS.
TOE-OUT ON TURNS (Fig. 16)
Toe-out on turns refers to the difference in angles
between the front wheels and the vehicle frame during
turns. Since the inner wheel turns a smaller radius than
the outer wheel, when rounding a curve, it must be at a
sharper angle with respect to the vehicle frame. That is,
the inner wheel must toe-out more than the outside
wheel toes-in. This condition is desirable because it
allows the front wheels to turn in a concentric circle.
Note in fig. 16 that the right front wheel centerline (B)
and the left front wheel centerline (C) intersect the
centerline of the rear axle (A) at the same point (D). The
20&deg; and 23&deg; angles are not necessarily representative of
any vehicle and are used here for theory only.
If “Toe-Out on Turns” is found to be other than
specified for a specific vehicle it might indicate that some
front suspension part is bent and a visual inspection is
necessary.
The angle of the steering arms is the determining factor
of toe-out on turns. If either arm is bent, toe-out on turns
will be affected.
This steering arm angle is not adjustable, so a bent arm
must be replaced. Since it is unlikely that both arms will
be bent, follow the procedure below to determine which,
if either, arm is bent.
Measurement
Measure the distance between the suspected bent arm
and a stationary point on the brake backing plate or
splash shield, comparing it with the same measurement
on the other arm. The angle of the steering arms must be
the same for both arms. Toe-out on turns is not
adjustable.
STEERING AXIS INCLINATION (S.A.I.) FIG. 17
Steering axis inclination (form ally called kingpin
inclination on conventional suspensions) is the inward
slant (at the top) of the steering knuckle from the
vertical. This inclination tends to reduce road shock on
the steering system by allowing the steering systems
centerline to intersect the tire centerline near the point
where the tire contacts the road. The inward slant or
inclination of the steering knuckle tends to keep the
wheels straight ahead. The reason for this is as follows:
When the front wheels are straight ahead the steering
knuckle spindles are practically horizontal. As the wheels
are turned away from the straight ahead the outer ends
of the spindle tries to lower or get closer to the ground.
However, because the spindles are fixed in the hub
assembly they cannot get closer, or lower, to the ground.
So the spindles force the steering knuckles to raise the
front of the vehicle.
After a turn is complete, and force applied to the
steering wheel is released, the weight of the vehicle on
the spindles tends to help the front wheels return to a
straight ahead position. “Steering Axis Inclination” is a
designed in angle and is non-adjustable.
PRELIMINARY ADJUSTMENTS FIG. 19-21
Before making any adjustment affecting caster, camber
or toe-in, the following checks and inspections should be
made to insure correctness of alignment readings and
alignment adjustments.
1. Check all tires for proper inflation pressures and
approximately the same tread wear.
2. Check front wheel bearings for looseness (.001-.008
end play is correct) and adjust if necessary.
3. Check for looseness of ball joints, tie rod ends and
steering relay rods, if excessive looseness is noted, it
must be corrected before adjusting.
4. Check for run-out of wheels and tires.
5. Check vehicle trim heights; if out of specifications
and a correction is to be made, the correction must
be made before adjusting caster, camber or toe-in.
NOTE: Good judgment should be exercised
before replacing a spring when vehicle trim
height is somewhat out of limits (&plusmn; 3 /4 &quot;).
6. Consideration must be given to excess loads, such as
tool boxes. If this excess load is normally carried in
the vehicle it should remain in the vehicle during
alignment checks.
7. Consider the condition of the equipment being used
to check alignment and follow the m anufacturer’s
instructions.
8. Regardless of equipment used to check alignment
the vehicle must be on a level surface both fore and
aft and transversely.
LIGHT DUTY TRUCK SERVICE MANUAL
FR ON T S U S PEN SIO N
3-11
Fig. 16—Toe-out on Turns
LIGHT DUTY TRUCK SERVICE MANUAL
3 12 FRONT SU SPEN SION
LEFT HAND FRONT VIEW
Fig. 17—Steering Axis Inclination
MAINTENANCE A N D ADJUSTMENTS
CAU TIO N : See CAUTION on page 1 of this
section regarding the fasteners referred to in
the maintenance and adjustment procedures
below.
WHEEL BEARINGS—CHECK ADJUSTMENT
Tapered roller bearings are used on
all series vehicles and they have a slightly loose
feel when properly adjusted. This differs from
ball bearings which may be pre-loaded without
adverse effect. A design feature of front wheel
taper roller bearings is that they must NEVER
be pre-loaded. Damage can result by the steady
thrust on roller ends which comes from preloading.
1. Raise car and support at front lower control arm.
2. Spin wheel to check for unusual noise.
3. If bearings are noisy or excessively loose, they
should be cleaned and inspected prior to
adjustment.
NOTE: To check for loose bearings, grip the
tire at the top and bottom and move the
wheel assembly in and out on the spindle.
CAUTIO N:
Movement greater than .008&quot; (.010&quot; on
K-Series) indicates a loose bearing. If
necessary to inspect bearings, see REPLACE&shy;
MENT OF BEARINGS.
ADJUSTMENT
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Raise car and support at front lower control arm.
Remove hub cap or wheel disc from wheel.
Remove dust cap from hub.
Remove cotter pin from spindle and spindle nut.
Adjust bearing as shown in Fig. 18.
Insert new cotter pin and bend ends against nut.
Cut off extra length to ensure ends will not interfere
with dust cap.
Install dust cap on hub.
Install hub cap or wheel disc.
Lower vehicle to ground.
Repeat this procedure for the other wheel.
FRONT ALIGNMENT (Fig. 19)
Satisfactory vehicle operation may occur over a wide
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
4.
H A N D ' S N U G -U P '
THE NUT
3 -1 3
5. LO O S E N N U T UNTIL EITHER HOLE
IN THE SPINDLE LINES UP W ITH
A SLOT IN THE N U T -T H E N
INSERT COTTER PIN.
N O T E : UNDER N O C IR C U M STAN C ES
IS THE B EAR IN G TO BE EVEN
FINGER TIGHT.
3. BACK OFF N U T
UNTIL JUST LO O SE
( 1 / 4 - 1 / 2 TURN)
&quot;S N U G -U P
THE N UT TO
FULLY SEAT BE A R IN G S—
THIS O V E R C O M E S A N Y
BURRS O N THREADS.
6. W H E N THE BEAR IN G IS PROPERLY
ADJUSTED THERE WILL BE FROM
. 0 0 1 - . 0 0 8 IN CHES END-PLAY
(LO O S E N E S S ).
Fig. 18—Wheel Bearing Adjustment
range of front end wheel alignment settings. Neverthe&shy;
less, should settings vary beyond certain tolerances,
readjustment of alignment is advisable. The specifica&shy;
tions stated in column 1 of the applicable vehicle chart
in the specifications section of this manual should be
used by owners, dealers and repairmen as guidelines in
vehicle diagnosis either for repairs under the new vehicle
warranty or for maintenance service at customer’s
request. These specifications provide an acceptable allaround operating range in that they prevent abnormal
tire wear caused by wheel alignment.
Governmental Periodic Motor Vehicle Inspection pro&shy;
grams usually include wheel alignment among items that
are inspected. To provide useful information for such
inspections, the specifications stated in column 2 of the
aforesaid applicable chart are given and these are well
within the range of safe vehicle operation.
In the event the actual settings are beyond the
specifications set forth in column 1 or 2 (whichever is
applicable), or whenever for other reasons the alignment
is being reset, Chevrolet recommends that the specifica&shy;
tions given in column 3 of the aforesaid applicable chart
be used.
NOTE: A normal shim pack will leave at
least two (2 ) threads of the bolt exposed
beyond the nut. If two (2) threads cannot be
obtained: Check for damaged control arms
and related parts. Difference between front
and rear shim packs must not exceed .30
inches. Front shim pack must be at least .24
inches.
Caster (Fig. 20)
All caster specifications are given assuming a frame
angle of zero. Therefore, it will be necessary to know the
angle of the frame (whether “up” in rear or “down” in
rear) before a corrected caster reading can be
determined. Camber and toe can be read “as is” from
the alignment equipment.
How to Determine Caster
1. With the vehicle on a level surface, determine the
frame angle “B” in Fig. 20, using a bubble
protractor or clinometer.
2. Draw yourself a graphic as in Fig. 20 that is
representative of the frame angle (either “up” in
rear or “down” in rear).
3. Determine the caster angle from the alignment
equipment and draw a line that is representative of
the caster reading.
4. To determine an “actual (corrected) caster reading”
with various frame angles and caster readings one
of the following rules applys.
a. A “ DOWN IN REAR” frame angle must be
SUBTRACTED from a POSITIVE caster reading.
b. An “ UP IN REAR” frame angle must be ADDED
to a POSITIVE caster reading.
c. A “ DOWN IN REAR ” frame angle must be
ADDED to a NEGATIVE caster reading.
d. An “ UP IN REAR” frame angle must be
SUBTRACTED from
a NEGATIVE caster
reading.
5. Add or subtract as necessary to arrive at the
corrected caster angle.
6 . Measure dimension “A ” (bump stop bracket to
frame) and check the specifications for that
dimension.
7. Correct the actual caster angle, as arrived at in Step
4, as necessary to keep within the specifications by
adding or subtracting shims from the front or rear
bolt on the upper control arm shaft (fig. 21 ).
Camber
1. Determine the camber angle from the alignment
equipment.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -1 4 FRONT SU S PEN SIO N
&lt;L OF WHEEL
&lt;L OF WHEEL
Vehicles within these tolerances from the mean
specification are safe and not hazardous with respect to
alignment effects on operation and handling. Settings
outside these limits are not necessarily unsafe, however,
customer dissatisfaction, due to steering pull or tire wear
may occur or the vehicle may be in a damaged
condition.
DEFINITIONS
CAMBER ANGLE
CASTER ANGLE
LEFT FRONT V IEW
LEFT SIDE VIE W
Service Checking
Values within these limits should provide a high level of
customer satisfaction and should not require resetting.
Service Reset
Values that the vehicle should be set within if it is
observed out of the service checking tolerance, or if it is
being aligned due to replacement of components, or for
any other reasons.
Fig. 19—Front Suspension Alignment
2. Add or subtract shims from both the front and rear
bolts to affect a change.
Toe-In
1. Determine the wheel toe-in from the alignment
equipment.
2. Change the length of both tie rod sleeves to affect a
toe change. See Section 9 for proper tie rod
positioning and orientation, torque tie rod clamps
to specifications.
Vehicle Inspection Tolerances
For government inspection station usage.
Toe-In Changing Fig. 22
Toe-in can be increased or decreased by changing the
length of the tie rods. A threaded sleeve is provided for
this purpose.
When the tie rods are mounted ahead of the steering
knuckle they must be decreased in length in order to
increase toe-in. W hen the tie rods are mounted behind
the steering knuckle they must be lengthened in order to
increase toe-in.
See Section 9 for proper tie rod clamp orientation and
positioning.
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT S U S PEN SIO N
3 -1 5
A
HORIZONTAL
FRAME ANGLE =
1V4&deg; DOWN
\
■CASTER ANGLE READING =
ACTUAL (CORRECTED) CASTER ANGLE =
+ (2!4&deg;)
+ (1 &deg; )
HORIZONTAL
\
FRAME ANGLE =
R ANGLE READING =
FRAME ANGLE = ’/a0 DOWN
CASTER ANGLE READING = - ( IV 4 0)
ACTUAL (CORRECTED) CASTER ANGLE =
- ( l 3/ 4 &deg; )
FRAME ANGLE = 114&deg; UP
+(2&deg;)
ACTUAL (CORRECTED) CASTER ANGLE = + (3 &deg; )
CASTER ANGLE READING =
ACTUAL (CORRECTED) CASTER ANGLE =
- ( V 4 &deg; )
+
0 &deg;)
CROSSMEMBER
Fig. 20—Determining Caster - Typical (C Series Shown)
LIGHT DUTY TRUCK SERVICE MANUAL
3 -1 6 FRONT SU SPEN SION
PIVOT SHAFT OUTBOARD OF FRAME
A
CASTER
CAMBER
FORWARD
Fig. 21—Caster - Camber Adjustment
Fig. 22—Toe-in Adjustment
C O M PO N EN T PARTS REPLACEMENT
WHEEL HUBS, BEARINGS (Fig. 23)
Removal C, G and P Series
1. Raise vehicle on hoist and remove wheel and tire
assembly. Remove dust cap from end of hub and
withdraw cotter pin.
2. Remove the brake caliper and hang by wire to the
suspension.
CAUTION: Do not allow the caliper assembly
to hang by the brake flex line.
3. Remove hub and disc assembly.
4. Remove outer bearing from hub. The inner bearing
will remain in the hub and may be removed by
prying out the inner grease seal.
5. Wash all parts in cleaning solvent.
Inspection
1. Check all bearings for cracked bearing cages, worn
or pitted rollers.
2. Check bearing races for cracks or scoring, check
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT S U S PEN SIO N
3 -1 7
brake discs for out-of-round or scored conditions
and check bearing outer races for looseness in hubs.
Repairs
Replacement o f Bearing Cups
If necessary to replace an outer race, drive out old race
from the hub with a brass drift inserted behind race in
notches in hub. Install new race by driving it into hub
with the proper race installer J-8457, J-8458, J-8849 or
J-9276-2. Remove and install the inner race in the same
manner.
CAUTION: Use care when installing new race
to start it squarely into hub, to avoid distortion
and possible cracking.
Thoroughly lubricate bearing assemblies with new high
melting point wheel-bearing lubricant. Remove any
excess lubricant.
NOTE: Be sure bearing parts have been
thoroughly cleaned and air-dried.
Fig. 23—Pressing Hub Bolt
Wheel Stud Replacement (Fig. 23)
NOTE: Use a piece of water pipe or other
similar tool to support the hub while pressing
a wheel stud either in or out.
Installation
1.
2.
3.
4.
5.
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 3, 4 and 5.
Pack inner and outer wheel bearings with
recommended grease (see Section 0).
Place inner bearing in hub and install new seal
assembly, tapping into place with soft hammer.
Position hub and disc on spindle and install outer
bearing, pressing it firmly into position in hub.
Install hub washer and finger tighten nut.
Install brake caliper see section 5.
Install wheel and tire, and adjust wheel bearings as
outlined under Wheel Bearings—Adjust, then lower
vehicle to floor.
SHOCK ABSORBER
Removal (Figs. 24 and 25)
1. Raise vehicle on hoist.
2. Remove nuts and eye bolts securing upper and
lower shock absorber eyes.
3. Withdraw shock absorber and inspect rubber eye
bushings. If defective, replace shock absorber
assembly.
Fig. 24—Shock Absorber - K Series
STABILIZER BAR-TYPICAL
Removal (Fig. 26)
1. Raise vehicle on hoist and remove nuts and bolts
attaching stabilizer brackets and bushings at frame
location.
2. Remove brackets and bushings at lower control
arms (spring anchor plates on K series) and remove
stabilizer from vehicle.
Inspection
Inspect rubber bushings for excessive wear or aging—
replace where necessary. Use rubber lubricant when
installing bushings over stabilizer bar.
Installation
Place shock absorber into position over mounting bolts
or into mounting brackets. Install eye bolts and nuts and
torque as shown in Specifications Section. Lower vehicle
to floor.
Installation
CAUTION: See CAUTION on page 1 o f this
section regarding the fasteners referred to in
step 2.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -1 8 FRONT SU SPEN SION
Fig. 25—Shock Absorber - C, P and G Typical
NOTE: Slit in bar to frame bushings should
be facing forward.
1. Place stabilizer in position on frame and install
frame brackets over bushings. Install nuts and bolts
loosely.
2. Install brackets over bushings at lower control arm
location. Be sure brackets are positioned properly
over bushings. Torque all nuts and bolts to
specifications.
3. Lower vehicle to floor.
Fig. 26B—Stabilizer Bar K-Typical
COIL SPRING
Removal (Fig. 27)
1. Place vehicle on hoist and place jack stands under
frame, allowing control arms to hang free.
2. Disconnect shock absorber at lower end and move
aside. Disconnect the stabilizer bar attachments to
the lower control arm.
Fig. 27—Removing Coil Spring with Tool J-23028
3. Bolt Tool J-23028 to a suitable jack.
4. Place tool under cross-shaft so that the cross-shaft
seats in the grooves of the tool. As a safety
precaution install and secure a chain through the
spring and lower control arm.
5. Raise the jack to remove tension on the lower
control arm cross-shaft and remove the two “U ”
bolts securing the cross-shaft to crossmember.
The cross-shaft and lower control
arm keeps the coil spring compressed. Use
care when lowering.
WARNING:
6 . Lower control arm by slowly releasing the jack until
Fig. 26A—Stabilizer Bar - C, P and G Typical
spring can be removed. Be sure all compression is
relieved from spring.
7. Remove spring.
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT S U S PEN SIO N
3 -1 9
Installation
1.
2.
3.
4.
5.
6.
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to steps
3 and 4.
Properly position spring on the control arm, and lift
control arm using jack and tool J-23028.
Position control arm cross-shaft to crossmember
and install “U ” bolts and attaching nuts. Make
certain front indexing hole in cross-shaft is lined up
with crossmember attaching saddle stud.
Torque nut to specifications.
Install shock absorber to lower control arm and
install stabilizer bar.
Remove tool J-23028 and safety chain.
Lower vehicle to floor.
LEAF SPRING AND BUSHINGS K SERIES
Removal
1. Raise vehicle on hoist.
2. Place adjustable lifting device under axle.
3. Position axle so that all tension is relieved from
spring.
4. Remove shackle upper retaining bolt.
5. Remove front spring eye bolt.
6 . Remove spring-to-axle u-bolt nuts and remove
spring, lower plate and spring pads.
7. Remove shackle to spring bolt and remove bushings
and shackle.
Bushing Replacement
1. Place spring on press and press out bushing using a
suitable rod, pipe, or tool.
2. Press in new bushing; assure that tool presses on
steel outer shell of bushing. Install until bushing
protrudes an equal amount on each side of spring.
Spring Inserts (Liners) or Leaf Replacement
1. Place spring in vise and remove clips.
2. Remove center bolt. Open vise slowly, allowing
spring to expand.
3. Wire brush, clean, and inspect for broken leaves.
4. Replace leaf or liners.
Installation
See CA UTION note on page one of
this section regarding the fasteners referred to
in steps 5 and 6.
1. Install spring shackle bushings into spring and
attach shackle. Do not tighten bolt.
2. Position spring upper cushion on spring.
3. Insert front of spring into frame and install bolt.
Do not tighten.
CAUTION:
Fig. 28—Leaf Spring Assembly K-Series
4. Install shackle bushings into frame and attach rear
shackle. Do not tighten bolt.
5. Install lower spring pad and spring retainer plate.
Torque bolts to specifications.
6 . Torque front and rear spring eye and shackle bolts
to specifications.
7. Remove stands and lower vehicle to floor.
UPPER CONTROL ARM INNER PIVOT
SHAFT
AND/OR BUSHING REPLACEMENT
C20-30, G30 and P10-30 (Steel Bushings)
Pivot Shaft Removal
1. Raise vehicle and remove tire and wheel assembly.
2. Support the lower control arm with a floor jack.
NOTE: Position jack under the ball joint
assembly or as near as possible and still have
good support.
3. Loosen the upper control arm shaft end nuts before
loosening the shaft to frame attaching nuts.
4. Loosen the shaft to frame nuts and remove the
caster and camber shims.
NOTE: Tape the shims together as they are
removed and mark for position.
5. Remove the pivot shaft to frame nuts but do not
allow the arm to swing too far away from the
frame.
NOTE: Use a safety chain to retain the arm
in a close relationship to the frame.
6 . Remove the shaft end nuts and remove shaft from
arm.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -2 0 FRONT SUSPENSION
LOWER CONTROL ARM INNER PIVOT
SHAFT
AND/OR BUSHING REPLACEMENT
C20-30, G30, P10-30 (Steel Bushings)
Lower—Removal (Fig. 29)
1. Raise vehicle and support the frame so that control
arms hang free.
2. Position an adjustable floor jack under the control
arm inboard of spring and into depression in lower
arm.
3. Install a chain over upper arm (Fig. 29). Inboard of
stabilizer and outboard of shock absorber as a
safety measure.
4. Disconnect shock absorber at lower control arm.
5. Loosen shaft end nuts.
6 . Remove “U ” bolts.
7. Lower jack just enough to get at shaft.
8 . Remove shaft end nuts and remove shaft.
Fig. 29—Removing Inner Pivot Shaft
Bushing Replacement (Steel Bushings)
1. Remove grease fittings from bushing outer ends
and unscrew bushings from control arm and shaft.
2. Slide new seal on each end of shaft and insert shaft
into control arm.
3. Start new bushings on shaft and into control arm.
Adjust shaft until it is centered in control arm, then
turn bushings in and torque to specifications. Figure
30 shows correct final positioning of shaft. Check
shaft for free rotation and install grease fittings.
Installation
See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 3, 5 and 6.
NOTE: When installing the upper control
arm be sure to properly position the special
aligning washers to the pivot shaft with
convex and concave sides together.
Install the shaft to the control arm and install end
nuts. Do not torque nuts at this time.
Position cross shaft to frame bolts and start cross
shaft nuts.
Torque the shaft end nuts. See Fig. 30 for proper
spacing.
NOTE: The shaft should rotate by hand after
the nuts are torqued.
Install caster and camber shim in their appropriate
places.
Torque the cross-shaft to frame nuts.
Remove the safety chain and install the tire.
Lower vehicle to the floor.
Bushing Replacement (Steel Bushings)
1. Remove grease fittings from ends of bushings and
unscrew bushings from shaft and control arm.
Remove shaft and seals.
2. Slide new seal on each end of shaft and insert shaft
into control arm.
3. Start new bushings on shaft and into control arm.
Adjust shaft until it is centered in control arm, then
turn bushings in and torque to specifications. Check
shaft for free rotation. Figure 31 shows correct final
positioning of shaft.
CAUTION:
1.
2.
3.
4.
5.
6.
7.
CP 20-30
■2%a'
Fig. 30—Positioning Upper Control Arm Shaft (Steel Bushings)
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
Installation
CAUTIO N :
1.
2.
3.
4.
5.
6.
7.
See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 4 and 5.
Install shaft to control arm and install end nuts. Do
not torque nuts at this time.
Raise jack and position shaft into crossmember
saddle. Be sure to index hole in shaft to mate with
bolt head in saddle.
Install “U ” bolts. Do not torque nuts at this time.
Torque cross-shaft end nuts.
NOTE: The shaft should roate by hand after
the nuts are torqued.
Torque “U ” bolt nuts.
Remove safety chain.
Lower vehicle to floor.
3-21
J—24435-7
J—24435-3
J—24435-1
Fig. 32A—Upper Control Arm Rubber Bushing
Removal
UPPER CONTROL ARM ASSEMBLY
24435-7
All Removal
1. Raise vehicle on hoist, remove wheel and tire
assembly and support lower control arm assembly
with adjustable jackstand.
2. Remove cotter pin from upper control arm ball stud
and loosen stud nut one turn.
3. Loosen upper control arm ball stud in steering
knuckle, using Tool J-23742 position as shown in
Figure 34. Remove the nut from the ball stud and
raise upper arm to clear steering knuckle.
J—24435-4
J—24435-5
(HIDDEN)
Fig. 32B—Upper Control Arm Rubber Bushing
Installation
NOTE: It is necessary to remove the brake
caliper assembly and wire it to the frame to
gain clearance for tool J-23742. See section 5
for proper clearance.
4. Remove nuts securing control arm shaft to frame.
Withdraw control arm assembly.
NOTE: Tape shims together and tag for
proper relocation when control arm is
reinstalled.
Upper Control Arm Inner Pivot Shaft
and/or Bushing Replacement
CIO , G10-20 (Rubber Bushings)
Fig. 31—Positioning Lower Control Arm Shaft (Steel
Bushings)
Removal (Fig. 32A)
1. Remove the upper control arm using the preceding
procedure and mount the control arm in a vise.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -2 2 FRONT SUSPENSION
2. Install remover J-24435-1, receiver J-24435-3 and
&quot;C &quot; clamps J-24435-7 as shown in Figure 32A.
3. Tighten the clamp to draw out the old bushing.
Discard old bushing.
4. The pivot shaft may now be removed from the
control arm assembly.
5. Reposition the control arm in the vise and repeat
the removal procedure on the remaining bushing.
Bushing Installation
1. Again using &quot;C &quot; clamp J-24435-7 and installers
J-24435-4 (outer) and J-24435-5 (inner) tighten
clamp to install bushing onto control arm.
2. Install pivot shaft into inside diameter of first
installed bushing.
3. Install remaining bushing as shown in figure 32B
and described in step 1.
4. Remove tools and install control arm on vehicle
following procedure described below. Torque all
fasteners to proper specifications.
Upper Control Arm Installation
See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 1, 2 and 3.
CAUTION:
1.
2.
3.
4.
5.
NOTE: When installing the upper control
arm be sure to position the special aligning
washers to the pivot shaft with concave and
convex sides together.
Place control arm in position on bracket and install
nuts. Before tightening nuts, insert caster and
camber shims in the same order as when removed.
Torque the nuts to specifications.
NOTE: A normal shim pack will leave at
least two (2 ) threads of the bolt exposed
beyond the nut. If two (2) threads cannot be
obtained: Check for damaged control arms
and related parts. Difference between front
and rear shim packs must not exceed .30
inches. Front shim pack must be at least .24
inches.
NOTE: Always tighten the thinner shim
packs’ nut first for improved shaft to frame
clamping force and torque retention.
Insert ball joint stud into steering knuckle and
install nut. Torque stud nut to specifications and
install cotter pin.
Install brake caliper assembly if removed (see
section 5).
Remove adjustable support from under lower
control arm. Install wheel and tire assembly.
Lower the vehicle to the floor.
LOWER CONTROL ARM ASSEMBLY
Removal
1. Raise vehicle on hoist and remove spring as
outlined under spring removal.
NOTE: Support the inboard end of the
control arm after spring removal.
2. Remove cotter pin from lower ball stud and loosen
stud nut one turn.
3. Install Ball Stud Remover J-23742, position large
cup end of the tool over the upper ball stud nut and
piloting the threaded end of tool on end of the
lower ball stud. Extend bolt from Tool J-23742 to
loosen lower ball stud in steering knuckle. When
stud is loosened, remove tool and nut from lower
stud.
NOTE: It is necessary to remove the brake
caliper assembly and wire it to the frame to
gain clearance for tool J-23742. See section 5
for proper procedure.
4. Remove the lower control arm.
Lower Control Arm Inner Pivot Shaft
and/or Bushing Replacement-On Vehicle
CIO, G10-20 (Rubber Bushings)
Removal (figs. 33A and 33B)
NOTE: If just bushings or pivot shaft are to
be replaced the lower control arm does not
have to be removed from the vehicle.
1. Raise vehicle on hoist and support the frame so
that the control arms hang free.
2. Position an adjustable floor jack under the lower con&shy;
trol arm inboard of spring and into depression of
control arm.
Fig. 33A—Lowering Control Arm for Bushing
Replacement
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
3 -2 3
J-24435-7
J-24435-6
Fig. 33B—Lower Control Arm Rubber Bushing
Removal
3. Install a chain over the upper arm inboard of the
stabilizer and outboard of shock absorber as a
safety measure.
4. Disconnect shock and stabilizer bar attachments at
lower control arm.
5. Loosen shaft end nuts.
6 . Remove &quot;U &quot; bolts that retain the inboard end of
the lower control arm.
7. Lower jack SLOWLY to release spring compression
(fig. 33A) and gain clearance to remove bushings.
WARNING: Be sure all compression is
released from coil springs.
8 . Bushings may now be replaced. Install &quot;C &quot; clamps
9.
10.
11.
12.
13.
J-24435-7 and receiver J-24435-3 with remover
J-24435-2 and spacer J-24435-6 as shown in figure
33B.
Remove the stakes on the front bushing using tool
J-22717 or equivalent tool.
Tighten the &quot;C&quot; clamp to remove the bushing.
Remove tools and discard old bushing.
Pivot shaft may now be removed if necessary.
Remove second bushing (leave pivot shaft in to
pilot tool) by the same method as in steps 8- 12.
Fig. 33C—Lower Control Arm Rubber Bushing
Installation
CAUTION: Be sure spacer J-24435-6 is in
position as shown in figure 33C to avoid
collapsing control arm during assembly.
3. Install one bushing then insert the pivot shaft and
install second bushing.
4. Stake front bushing at least in two places when
installed.
5. Install the lower control arm to the vehicle as
described under &quot;Lower Control Arm - Installa&shy;
tion&quot;, being sure to torque all fasteners to the
proper specification.
Lower Control Arm Installation
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 2 and 3.
1. Install lower ball stud through steering knuckle and
tighten nut.
2. Install spring and control arm as outlined under
spring installation.
3. Torque lower control arm ball stud to specifications
and install cotter pin.
4. Install brake caliper assembly if removed (see
section 5).
5. Lower the vehicle to the floor.
Bushing Installation (fig. 33C)
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
step 5.
1. Install new bushings as shown in figure 33C using
spacer J-24435-6, installer J-24435-4 and &quot;C &quot; clamp
J-24435-7.
2. Turn clamp in until bushing seats firmly.
BALL JOINT SERVICE—ON VEHICLE
Ball Joint—Inspection
The upper ball stud is spring loaded in its socket. This
minimizes looseness at this point and compensates for
normal wear, if the upper stud has any perceptible
lateral shake, or if it can be twisted in its socket with the
fingers, the upper ball joint should be replaced.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -2 4 FRONT SU SPEN SION
4.
5.
6.
7.
8.
torque to align cotter pin not to exceed 130 ft.
lbs. Never back off1to align cotter pin.
Install new cotter pin.
Install lube fitting and lube new joint.
Install brake caliper assembly if removed (see
section 5).
Install tire and wheel assembly.
Lower the vehicle to the floor.
Ball Joint—Inspection
Lower
Fig. 34—Disconnecting Ball Joints—Typical
Upper—Removal
1. Raise vehicle on hoist. If a frame hoist is used, it
will be necessary to support the lower control arm
with a floor jack.
2. Remove cotter pin from upper ball stud and loosen
stud nut (two turns) but do not remove nut.
3. Install J-23742 between the ball studs as shown in
Figure 34.
NOTE: It is necessary to remove the brake
caliper assembly and wire it to the frame to
gain clearance for tool J-23742. See section 5
for the proper procedure.
Before proceeding with Step 4, be
sure lower control arm is supported as pointed
out in Step 1.
CAUTION:
4. Extend bolt from Tool J-23742 to loosen ball stud in
steering knuckle. When stud is loose, remove tool
and stud nut.
5. Center punch rivet heads and drill out rivets.
6 . Remove the ball joint assembly.
Lower ball joints are a loose fit when not connected to
the steering knuckle. W ear may be checked without
disassembling the ball stud, as follows:
1. Support weight of control arms at wheel hub and
drum.
2. Accurately measure distance between tip of ball
stud and tip of grease fitting below ball joint.
3. Move support to control arm to allow wheel hub
and drum to hang free. Measure distance as in Step
2. If the difference in measurements exceeds .094”
(3/32”) for all models, ball joint is worn and should
be replaced (fig. 35).
Lower—Removal
1. Raise vehicle on a hoist. If a frame hoist is used it
will be necessary to support the lower control arm
with a floor stand.
2. Remove the tire and wheel assembly.
3. Remove the lower stud cotter pin and loosen (two
turns) but do not remove the stud nut.
4. Install J-23742 between the ball studs as shown in
Figure 34.
NOTE: It is necessary to remove the brake
Installation
CAUTION:
See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 1, 3 and 6.
1. Install new service ball joint, using bolts and nuts
supplied with joint, to upper arm. Torque nuts to 45
ft. lbs.
2. Mate ball stud to steering knuckle and install stud
nut.
3. Torque the ball stud nut as follows:
A. 10 Series 40—60 ft. lbs. plus additional torque to
align cotter pin not to exceed 90 ft. lbs. Never
back off to align cotter pin.
B. 20—30 Series 80—100 ft. lbs. plus additional
Fig. 35—Checking Lower Ball Joint
LIGHT DUTY TRUCK SERVICE MANUAL
F RONT S U S PEN SIO N
caliper assembly and wire it to the frame to
gain clearance for tool J-23742. See section 5
for proper procedure.
CAUTION: Before proceeding with Step 5, be
sure lower control arm is supported as pointed
out in Step 1.
5. Extend bolt from Tool J-23742 to loosen ball stud in
steering knuckle. When stud is loosened, remove
tool and ball stud nut.
6 . Pull the brake disc and knuckle assembly up off the
ball stud and support the upper arm with a block of
wood so that assembly is out of working area.
CAUTION:
Do not put stress on the brake line
flex hose.
WATER PIPE
3 -2 5
7. Install Tools J-9519-10 and J-9519-7 as shown in
Fig. 36.
NOTE: It will be necessary to alter Tool
J-9519-10 as illustrated in Fig. 37 and install
a 3” I.D. pipe as shown if working on a 20 or
30 series vehicle.
8 . Turn hex head screw until ball joint is free of
control arm.
9. Remove tools and the ball joint.
Installation (Fig. 38)
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 4, 5 and 7.
1. Start the new ball joint into the control arm and
install J-9519 and J-9519-9 as shown.
NOTE: Position bleed vent in rubber boot
facing inward.
2. Turn hex head screw until ball joint is seated in
control arm.
3. Lower the upper arm and mate the steering knuckle
to the lower ball stud.
4. Install brake caliper assembly if removed (see
Section 5).
5. Install ball stud nut and torque as follows. All
Series, 80—100 ft. lbs. plus additional torque to
align cotter pin hole not to exceed 130 ft. lbs.
maximum. Never back off to align cotter pin.
6 . Install a lube fitting and lube the joint.
7. Install tire and wheel assembly and lower vehicle to
floor.
STEERING KNUCKLE
Fig. 36—Ball Joint Removal
It is recommended that vehicle be raised and supported
as on a twin-post hoist so that the front coil spring
Fig. 37—Alteration to Tool J-9519-10
Fig. 38—Installing Ball Joint
LIGHT DUTY TRUCK SERVICE MANUAL
3 -2 6 FRONT SU SPEN SION
remains compressed, yet the wheel and steering knuckle
assembly remain accessible. If a frame hoist is used,
support lower control arm with an adjustable jackstand
to safely retain spring in its curb height position.
Removal
1. Raise vehicle on hoist and support lower control
arm as noted above.
2. Remove wheel and tire assembly.
3. Remove caliper as outlined under “Front Wheel
Hub - Removal” .
4. Remove disc splash shield bolts securing the shield
to the steering knuckle. Remove Shield.
5. Refer to Section 9 — Steering Linkage — Tie Rod,
for service removal operations.
6 . Remove upper and lower ball stud cotter pins and
loosen ball stud nuts. Free steering knuckle from
ball studs by installing Special Tool J-23742.
Remove ball stud nuts and withdraw steering
knuckle.
Removal (Fig.
Installation
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 2, 3, 4 and 5.
1. Place steering knuckle in position and insert upper
and lower ball studs into knuckle bosses.
Steering knuckle hole, ball stud and
nut should be free of dirt and grease before
tightening nut.
CAUTION:
2. Install ball stud nuts and tighten nut to specifica&shy;
tions. (See Specification Section.)
If necessary, tighten one more
notch to insert cotterpins. Do not loosen nut to
insert cotter pin. Refer to Ball Joint text for
proper nut installation sequence.
CAUTION:
3. Reverse remaining removal procedure, and tighten
splash shield mounting bolt. Tighten two caliper
assembly mounting bolts tO 35 ft. lb. torque.
4. Adjust wheel bearings as outlined under Front
Wheel Bearing Adjustment.
5. Tighten wheel nuts to 75 ft. lb.
CROSSMEMBER AND SUSPENSION UNIT
Component parts of the front suspension may be
serviced separately as outlined in the preceding service
operations. However, if extensive service is to be
performed to crossmember, frame, etc., the unit can be
removed and installed as follows:
39)
1. Place vehicle on hoist and remove the shock
absorber from the lower control arm.
2. Remove idler arm and pitman arm.
3. Support engine and remove front engine mount
center bolts.
4. Separate main brake feeder line from crossmember
tee.
5. Remove bolts retaining crossmember hangers to
frame side rails.
6 . Remove bolts securing crossmember to frame
bottom rail and lower the assembly from vehicle.
Installation
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 1, 2, 3, 4, 5, 6 and 7.
1. Jack crossmember into position under frame and
install frame bottom rail mounting bolts.
2. Install bolts securing crossmember hanger to frame
and torque nuts. See specifications.
3. Position engine on front mount and install
mounting bolt and torque (see Section 6 ).
4. Install the shock absorber.
5. Connect front brake main feeder line and bleed
brakes as described in Section 5.
6 . Install idler arm and pitman arm (see Section 9).
7. Check and Adjust front end alignment as outlined
under “M aintenance and Adjustments” in this
section.
8 . Lower the vehicle to the floor.
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
3-27
FRONT SUSPENSION D IA G N O S IS
HARD STEERING
Probable Cause
a.
b.
c.
d.
e.
Probable Remedy
Ball joints and steering linkage need lubrication
Low or uneven front tire pressure
Power steering partially or not operative
Steering gear not properly adjusted
Incorrect front wheel alignment (manual steering)
a.
b.
c.
d.
e.
Lubricate ball joints and linkage
Inflate tires to the proper recommended pressure
Check power steering components for proper operation
Adjust steering gear
Check and align front suspension
POOR DIRECTIONAL STABILITY
a.
b.
c.
d.
e.
f.
gh.
Ball joints and steering linkage need lubrication
Low or uneven front or rear tire pressure
Loose wheel bearings
Steering Gear not on high point
Incorrect front wheel alignment (caster)
Broken springs
Malfunctioning shock absorber.
Broken stabilizer bar, or missing link
a.
b.
c.
d.
e.
f.
g.
h.
Lubricate at proper intervals
Inflate tires to the proper recommended pressure
Adjust wheel bearings
Adjust steering gear
Check and align front suspension
Replace springs
Diagnose shock absorbers.
Replace stabilizer or link
FRONT WHEEL SHIMMY
a.
b.
c.
d.
e.
(SMOOTH ROAD SHAKE)
Tire and wheel out of balance, or out of round
a. Balance tires, check run-out
Worn or loose wheel bearings
b. Adjust wheel bearings
Worn tie rod ends
c. Replace tie rod end
Worn ball joints
d. Replace ball joints
e. Diagnose shock absorbers
Malfunctioning shock absorber
VEHICLE PULLS TO ONE SIDE
a.
b.
c.
d.
(NO BRAKING ACTION)
Low or uneven tire pressure
a. Inflate tires to the proper recommended pressure
Front or rear brake dragging
b. Adjust brakes
Broken or sagging front spring
c. Replace spring
Incorrect front wheel alignment (Camber)
d. Check and align front suspension
EXCESSIVE PLAY IN STEERING
a. Incorrect steering gear adjustment
b. Worn steering gear parts
a. Adjust steering gear
b. Overhaul Gear (See sec. 9)
Fig. 40—Front Suspension Diagnosis
LIGHT DUTY TRUCK SERVICE MANUAL
3 -2 8 FRONT SU SPEN SION
N O IS E
IN
FRO NT
EN D
P ro b a b le C a u s e
a.
b.
c.
d.
e.
f.
gh.
i.
P ro b a b le R e m e d y
Ball joints and steering linkage need lubrication
Shock absorber loose or bushings worn
Worn control arm bushings
Worn tie rod ends
Worn or loose wheel bearings
Loose stabilizer bar
Loose wheel nuts
Spring improperly positioned
Loose suspension bolts
a.
b.
c.
d.
e.
f.
gh.
i.
Lubricate at recommended intervals
Tighten bolts and/or replace bushings
Replace bushings
Replace tie rod ends
Adjust or replace wheel bearings
Tighten all stabilizer bar attachments
Tighten the wheel nuts to proper torque
Reposition
Torque to specifications or replace
W HEEL TRAM P
a.
b.
c.
d.
Tire and wheel out of balance
Tire and wheel out of round
Blister or bump on tire
Improper shock absorber action
a.
b.
c.
d.
Balance wheels
Replace tire
Replace tire
Replace shock absorber
E X C E S S IV E OR U N E V E N T IR E W E A R
a.
b.
c.
d.
e.
Underinflated or overinflated tires
Improper toe-in
Wheels out of balance
Hard Driving
Over loaded vehicle
a.
b.
c.
d.
e.
Inflate tire to proper recommended pressure
Adjust toe-in
Balance wheels
Instruct driver
Instruct driver
S C U F F E D T IR E S
a.
b.
c.
d.
Toe-in incorrect
Excessive speed on turns
Tires improperly inflated
Suspension arm bent or twisted
a.
b.
c.
d.
Adjust toe-in to specifications
Advise driver
Inflate tires to proper recommended pressure
Replace arm
C UPPED T IR E S
a.
b.
c.
d.
e.
Front shock absorbers defective
Worn ball joints
Wheel bearings incorrectly adjusted or worn
Wheel and tire out of balance
Excessive tire or wheel runout
a.
b.
c.
d.
e.
Replace shock absorbers
Replace ball joints
Adjust or replace wheel bearings
Balance wheel and tire
Compensate for runout - (See Section 10 Theory
and Diagnosis)
Fig. 41—Front Suspension Diagnosis
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
3 -2 9
“ D O G &quot; T R A C K IN G
P ro b a b le R e m e d y
P r o b a b le C a u s e
LEAF TYPE REAR SPRING
a. Rear leaf spring broken
b. Bent rear axle housing
c. Frame or underbody out of alignment
a. Replace spring
b. Replace housing
c. Align frame
COIL TYPE REAR SPRING
a. Damaged rear suspension arm and/or worn bushings
b. Frame out of alignment
c. Bent rear axle housing
a. Replace suspension arm and/or bushings
b. Align frame
c. Replace housing
R E T U R N A B IL IT Y
a.
b.
c.
d.
e.
f.
g-
Steering column alignment
Steering linkage needs lubrication
Idler arm bushing worn
Steering gear adjustment
Power steering gear valve spool binding
Obstruction within power steering gear
Improper caster setting (negative)
POOR
a.
b.
c.
d.
e.
f.
g.
See Section 9 in shop manual for proper alignment
Lubricate chassis
Replace idler arm
Adjust gear as outlined in Section 9 of shop manual
See Section 9 in shop manual
See Section 9 in shop manual
Check and reset if necessary
E R R A T IC S T E E R IN G ON B R A K E A P P L IC A T IO N
a.
b.
c.
d.
Low or uneven tire pressure
Front wheel bearing incorrectly adjusted
Brakes incorrectly or unevenly adjusted
Front spring sagged
e. Steering gear off high point
f. Incorrect or uneven caster
g- Leaking wheel cylinders
a.
b.
c.
d.
Inflate tires to proper recommended pressure
Adjust bearing as necessary
Adjust brakes as necessary
Check shop manual for proper riding heights and
replace spring if necessary
e. Check and correct steering if necessary
f. Check and adjust caster as necessary
g. Replace (See sec. 5)
Fig. 42—Front Suspension Diagnosis
LIGHT DUTY TRUCK SERVICE MANUAL
3 -3 0 FRONT SU SPEN SION
B A L L J O IN T D IA G N O S T IC P R O C E D U R E
Fig. 43—Ball Joint Diagnostic Procedure except K Series
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
SHOCK ABSORBER
DIAGNOSIS
ON VEHICLE CHECKS
(Follow the Procedures Outlined Below in the Order
Indicated).
Preliminary Inspection and Ride Test:
Tire Pressure
Check tire pressure compare to vehicle specifications and
adjust as required. Poor vehicle control and ride
complaints are caused in many cases by improper tire
inflation.
Special Suspension Equipment
Check Service Parts Identification Sticker for any special
suspension equipment; such as, a heavy duty suspension.
Vehicles equipped with this type of option have a
somewhat stiffer or harsh ride, and this should be kept in
mind during the following tests. If complaint about
stiffness should occur while vehicle is still new (under
5,000 miles), owner should be advised to have ride
rechecked after 7,000 to 8,000 miles.
Vehicle Load Conditions
Note any exceptional load conditions under which the
owner normally operates the vehicle; such as, large tool
boxes full of tools, pick up bed full etc. If exceptional
loading is apparent, check the distribution of this weight.
Note if it is all toward one side of the vehicle or at the
extreme rear of the vehicle. Reposition load as required
to obtain a more uniform weight distribution.
the up and down motion stops very quickly. If up and
down motion continues longer at one corner when
compared to opposite corner (example, both front
shocks), the one having the longer up and down motion
may be suspect. Do Not compare front to rear. If
complaint is noise, this test should help to locate the
suspected area.
Inspecting Shock Mountings
If noisy and/or loose shock mountings are suspected,
place vehicle on hoist that supports wheels and check all
mountings for the following conditions:
(1) Worn or defective grommets
(2) Loose mounting nuts
(3) Possible interference condition
(4) Bump stops missing
If no apparent defects are noted in this step but noise
condition still exists when vehicle is bounced up and
down, proceed.
Inspecting Shocks for Leaks and
Manually Operating Shocks
This procedure is sub-divided into two general areas, (1)
Inspecting Shocks for Loss of Hydraulic Fluid and (2)
Manually Operating Shock. It should aid the technician
to localize defective shocks caused by internal noise in
the shock, weak, leaking, etc.
1.
Check Vehicle Ride and Handling
After completing previous checks, ride vehicle with
owner to determine if problem has been corrected or to
definitely establish type of problem that still exists. If
problem still exists (poor handling, bottoming, noise,
ride sway, etc.), proceed.
Inspecting and Testing the Shocks
Three procedures are included in this step. Thet are (a)
Bounce Test, (b) Inspecting Shock Mountings for Noise
(Looseness) and (c) Manually Operating Shocks to
Determine if Shocks are Weak, Leaking Hydraulic Fluid,
and/or if Shocks have an Internal Noise Condition.
IMPORTANT: Test procedures (b) and (c)
require vehicle to be on a hoist that supports
wheels or rear axle housing and front lower
control arms.
Bounce Test
NOTE: This is only a comparison type test to
help locate the suspected shock or noise
condition before proceeding.
Test each front and rear shock by bouncing each corner
of the vehicle. This can usually be done by lifting up and
pushing down on the end of the bumper near each
corner of the vehicle until maximum movement up and
down is reached. Then let go of bumper and observe if
3-31
2.
Inspecting Shocks for Possible Loss of Hydraulic
Fluid.
(a) Disconnect each shock lower mounting as
required and pull down on the shock until it is
fully extended.
(b) Inspect shocks for leaks in seal cover area.
Shock fluid is a very thin hydraulic fluid and
has a characteristic odor and dark brown tint
(Figure 44).
Certain precautions should be observed when
inspecting shocks for leaks:
• shocks may have glossy paint on them. Do
not confuse this paint with a leak condition.
• a slight trace of shock fluid around the seal
cover area is not cause for replacement. The
shock seal is engineered to permit a slight
seepage to lubricate the rod. The shock
absorber has reserve fluid to compensate for
the slight seepage.
• shocks are sometimes incorrectly diagnosed
as leakers due to oil spray originating from
some other source. If in doubt, wipe the wet
area from and manually operate shock as
described in Step (2). Fluid will reappear if
shock is leaking.
Manually Operating Shocks.
NOTE: It may be necessary with certain
types of shock mountings to fabricate a
LIGHT DUTY TRUCK SERVICE MANUAL
3 -3 2 FRONT SU SPEN SION
bracket that can be installed on a shock to
enable a technician to securely grip the shock
when manually operating the shock. See
Figure 45 for suggested methods of providing
temporary grip.
This test should help the mechanic to isolate the
following shock defects:
• loose piston
• binding condition internally
• verify leaking shock
• improper or defective valving
(a) If suspected problem is in front shocks,
disconnect both front shock lower mountings
and stroke each shock as follows: Grip the
lower end of the shock securely and pull down
(rebound stroke) then push up (compression
stroke). The control arms will limit the
movement of the front shocks during the
compression stroke. Compare the rebound
resistance between both front shocks, then
compare the compression resistance. If a
noticeable difference can be felt during either
stroke, usually the shock having the least
resistance is at fault.
(b) If shock has an internal noise condition, extend
shock fully, then exert an extra pull. If a small
additional movement is felt, a loose piston is
indicated and shock should be replaced. Other
noise conditions that require shock replace&shy;
ment are:
• a grunt or squeal after one full stroke in both
directions
• a clicking noise on fast reverse
• a skip or lag at reversal near mid-stroke
IM PORTANT: When air adjustable shocks
are being manually operated, the air line
must be disconnected at the shock absorber.
BENCH CHECKS
The bench checks are recommended if the proper type
hoist is not available to perform the “on car” tests, or if
there is still some doubt as to whether the shocks are
defective. In addition, the bench test allows a more
thorough visual inspection.
Bench check procedures are discussed for three general
types of shocks.
SPIRAL GROOVE RESERVOIR
IMPORTANT: If this type of shock has been
stored or allowed to lay in a horizontal
position for any length of time, an air void
will develop in the pressure chamber of the
shock absorber. This air void if not purged,
can cause a technician to diagnose the shock
as defective. To purge the air from the
pressure chamber, proceed as follows: (Refer
to figure 46)
(a) Holding the shock in its normal vertical position
(top end up), fully extend shock.
(b) Hold the top end of the shock down and fully
collapse the shock.
(c) Repeat Steps (a) and (b) at least five (5) times to
assure air is purged.
Bench Test Procedure
1. This is a comparison type test. If possible, obtain a
new or known good shock with same part number
as shock under test.
2. With shocks in vertical position (top end up), clamp
bottom mounts in vise.
CAUTION: Do not clamp on reservoir tube or
mounting threads.
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
TYPICAL REAR SHOCK
TYPICAL FRONT SHOCK
-U r
BOTTOM
M OUNT \
BOTTOM
M OUN T
ROD EXTENDED
(REBOUND) s.
SHOCK
COLLAPSED
BOTTOM
M OUNT
ROD EXTENDED
(REBOUND) '
BOnOM
TOP END
DOWN
INVERT
TH EN C OLLAPSE
m
VlUUli
o u nI t\, Î
mrrg
SHOCK COLLAPSED
•I I
TOP END
DOWN
INVERT. TH E N C OLLA PS E
Fig. 46—Position for Purging Air From Shocks
3. Manually pump each shock by hand at various
rates of speed and compare resistance of suspected
shock with the new one.
NOTE: Rebound resistance (extending the
shock) is normally stronger than the compres&shy;
sion resistance (approximately 2:1). However,
resistance should be smooth and constant for
each stroking rate.
4. Observe or listen for the following conditions that
will indicate a defective shock:
• a skip or lag when reversing stroke at mid travel.
• seizing or binding condition except at extreme
end of either stroke.
• a noise, such as a grunt or squeal, after
completing one full stroke in both directions.
• a clicking type noise at fast reversal.
• fluid leakage.
5. To check for a loose piston, completely extend
shock to full rebound; then exert an extra hard pull.
If a give is felt, a loose piston is indicated and
shock should be replaced.
PLIACELL OR GENETRON
Pliacell and Genetron are some of the trade names used
to indicate a gas-filled cell in the shock reservoir. The
reservoirs of Pliacell and Genetron shocks are smooth,
compared to the spiral groove type. The cell takes the
place of air in the reservoir. Thus, aeration or foaming
of the fluid is eliminated, as air and fluid cannot mix.
Due to this feature, these shocks should be bench
checked in an inverted position (top end down). If, when
stroked, a lag is noticed, it means the gas-filled cell has
been ruptured, and the shock should be replaced. If no
lag is noticed, the remainder of the bench check is the
same as given in the Spiral Groove Reservoir, Section 1,
Bench Check Procedure.
3 -3 3
AIR ADJUSTABLE SHOCKS
This type of shock contains an air chamber like the
spiral groove reservoir type, and must have the air
purged from the working chamber. See Section 1, Spiral
Groove Reservoir. After air has been purged from shock,
proceed as follows:
(a) Clamp lower shock mounting ring in vise in
vertical position with larger diameter tube at the
top.
(b) Pump unit by hand at different rates of speed.
Smooth resistance should be felt through the
length of the stroke. Since the units are normally
pressurized, the sound of air bubbles or a gurgling
noise is normal.
(c) The rem ainder of the bench check is the same as
given in the Spiral Groove Reservoir, Section 1,
Bench Check Procedure.
BEARINGS AND RACES
BENCH DIAGNOSTIC PROCEDURE
This section describes common types of bearing distress
and their causes. Illustrations are included to help
diagnose the cause of distress and comments are
provided to help make effective repairs.
Consider The Following Factors When
Diagnosing Bearing Distress:
1. Note General Condition of all
teardown and examinations.
2. Classify the failure with the
illustrations where possible.
3. Determine the cause. Recognizing
permit correction of the problem
repeat failure of the same type.
4. Make all repairs following
procedures.
parts during
aid of these
the cause will
and prevent a
recommended
Common Causes For Bearing Distress
Includes The Following:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Improper adjustment or preloading.
Mounting or teardown abuse.
Improper mounting methods.
Inadequate or wrong lubricants.
Entrance of dirt or water.
W ear from dirt or metal chips.
Corrosion or rusting.
Seizing or smearing from overload.
Overheating causing tempering.
Frettage of bearing seats.
Brinelling from impact loads and shipping.
M anufacturing defects.
Fatigue pitting and spalling.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -3 4 FRONT SU S PEN SIO N
DIAGNOSIS
FRONT WHEEL, PINION, DIFFERENTIAL SIDE AND REAR WHEEL ROLLER BEARINGS
EXCESS NOISE C O M PLA IN T
D IAG NO STIC PROCEDURE
Road Test
1.
2.
3.
4.
5.
Check tires for irregular wear
Check tire pressure
Check lubricant level
Drive to warm-up rear axle
Test at various speeds in drive, float, coast and cornering
Tire Noises
1.
2.
3.
4.
5.
Change tire pressure to minimize noises
Drive over different road surfaces
Smooth black-top minimizes tire noise
Cross switch tires, if necessary
Snow tire treads and studs caused added noises
Engine or
Exhaust
Noises
1.
2.
3.
4.
Drive slightly above speed where noise occurs, place transmission in neutral
Let engine speed drop to idle
Stop car
Run engine at various speeds
Test for
Wheel Bearing
Noise
1.
2.
3.
4.
1.
2.
3.
4.
Drive car at low speed on a smooth road
Turn car to develop left and right motions, traffic permitting
Noise should change due to cornering loads
Jack-up wheels to verify roughness at wheels
Drive car at low speed on a smooth road
Constant low pitch bearing noise may be heard
Noise should not change in reversing turns
Noise pattern should vary with wheel speed
1.
2.
3.
4.
5.
6.
7.
Roughness or whine noise should increase with speed
Noise pitch should be higher than differentials
Test on smooth road to minimize tire noises
Test at various speeds in drive, float, and coast
Rear pinion bearing noise may be louder on acceleration
Front pinion bearing noise may be louder on deceleration
Gear noises tend to peak in a narrow speed range
Test for
Differential
Bearing Noise
Test for
Pinion Bearing
iNoise
Fig. 47—Bearing Diagnosis
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
FRONT
3 -3 5
WHEEL B E A R IN G D IA G N O S IS
CONSIDER THE FOLLOWING FACTORS WHEN DIAGNOSING BEARING CONDITION:
1. GENERAL CONDITION OF A LL PARTS DURING DISASSEMBLY AND INSPECTION.
2. CLASSIFY THE FAILURE WITH THE A ID OF THE ILLUSTRATIONS.
3. DETERMINE THE CAUSE.
4
ABRASI VE
MAKE ALL REPAIRS FOLLOWING RECOMMENDED PROCEDURES.
WEAR
ROLLER
GALLING
BENT CAGE
PATTERN ON RACES AND ROLLERS CAUSED BY
FINE ABRASIVES.
METAL SMEARS ON ROLLER ENDS DUE TO OVERHEAT,
LUBRICANT FAILURE OR OVERLOAD (WAGON'S)
CAGE DAMAGE DUE TO IMPROPER HANDLING
OR TOOL USAGE.
CLEAN A LL PARTS AND HOUSINGS. CHECK SEALS
AND BEARINGS AND REPLACE IF LEAKING, ROUGH
OR NOISY.
REPLACE BEARING - CHECK SEALS AND CHECK
FOR PROPER LUBRICATION.
REPLACE BEARING.
....
AB RAS I VE
STEP W E A R
PATTERN ON ROLLER ENDS CAUSED BY
FINE ABRASIVES
CLEAN A LL PARTS AND HOUSINGS. CHECK SEALS
AND BEARINGS AND REPLACE IF LEAKING, ROUGH
OR NOISY.
All
ETCHING
BEARING SURFACES APPEAR GRAY OR GRAYISH
BLACK IN COLOR WITH RELATED ETCHING AWAY
OF MATERIAL USUALLY AT ROLLER SPACING.
BENT
|:i;s;:;:ii!J , . J i S j
CAGE
CAGE DAMAGE DUE TO IMPROPER HANDLING
OR TOOL USAGE.
REPLACE BEARING
REPLACE BEARINGS CHECK SEALS AND CHECK
FOR PROPER LUBRICATION.
%
nmm
INDENTATIONS
SURFACE DEPRESSIONS ON RACE AND ROLLERS
CAUSED BY HARD PARTICLES OF FOREIGN MATERIAL.
CLEAN ALL PARTS AND HOUSINGS. CHECK SEALS
AND REPLACE BEARINGS IF ROUGH OR NOISY.
CAGE
WEAR
WEAR AROUND OUTSIDE DIAMETER OF CAGE AND
ROLLER POCKETS CAUSED BY ABRASIVE MATERIAL
AND INEFFICIENT LUBRICATION.
CLEAN RELATED PARTS AND HOUSINGS.
CHECK SEALS AND REPLACE BEARINGS.
M ISALIG NM ENT
OUTER RACE MISALIGNMENT
CLEAN RELATED PARTS AND REPLACE BEARING.
MAKE SURE RACES ARE PROPERLY SEATED.
Fig. 48—Bearing Diagnosis
LIGHT DUTY TRUCK SERVICE MANUAL
3 -3 6 FRONT SUSPENSION
FRONT WHEEL BEARING DIAGNOSIS
CRACKED INNER
RACE
FATI GUE
SPALLING
RACE CRACKED DUE TO IMPROPER FIT,
COCKING, OR POOR BEARING SEATS.
FLAKING OF SURFACE M ETAL RESULTING FROM
FATIGUE
REPLACE BEARING AND CORRECT BEARING
SEATS.
REPLACE BEARING - CLEAN A L L RELATED PARTS.
FRETTAGE
CORROSION SET UP BY SMALL RELATIVE
MOVEMENT OF PARTS WITH NO LUBRICATION.
REPLACE BEARING. CLEAN RELATED PARTS.
CHECK SEALS AND CHECK FOR PROPER LUBRICATION.
(CONT’D)
BRINELLI NG
SURFACE INDENTATIONS IN RACEWAY CAUSED BY
ROLLERS EITHER UNDER IMPACT LOADING OR
VIBRATIO N WHILE THE BEARING IS NOT ROTATING.
REPLACE BEARING IF ROUGH OR NOISY.
STAI N
D I S COL OR AT I ON
HEAT
DI SCOLORATI ON
DISCOLORATION CAN RANGE FROM LIGHT BROWN
TO BLACK CAUSED BY INCORRECT LUBRICANT OR
MOISTURE.
HEAT DISCOLORATION CAN RANGE FROM FAINT
YELLOW TO DARK BLUE RESULTING FROM OVER
LOAD OR INCORRECT LUBRICANT.
RE USE BEARINGS IF STAINS CAN BE REMOVED BY
LIGHT POLISHING OR IF NO EVIDENCE OF OVER
HEATING IS OBSERVED.
EXCESSIVE HEAT CAN CAUSE SOFTENING OF RACES
OR ROLLERS.
CHECK SEALS AND RELATED PARTS FOR DAMAGE.
TO CHECK FOR LOSS OF TEMPER ON RACES OR
ROLLERS A SIMPLE FILE TEST MAY BE MADE. A
FILE DRAWN OVER A TEMPERED PART W ILL GRAB
AND CUT METAL, WHEREAS, A FILE DRAWN OVER A
HARD PART W ILL G LIDE RE A DILY WITH NO METAL
CUTTING.
REPLACE BEARINGS IF OVER HEATING DAMAGE IS
INDICATED. CHECK SEALS AND OTHER PARTS.
SMEARS
SMEARING OF METAL DUE TO SLIPPAGE.
SLIPPAGE CAN BE CAUSED BY POOR FITS.
LUBRICATION, OVERHEATING, OVERLOADS
OR HANDLING DAMAGE.
REPLACE BEARINGS, CLEAN RELATED PARTS
AND CHECK FOR PROPER FITS AND
LUBRICATION
Fig. 49—Bearing Diagnosis
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SUSPENSION
1.
2.
3.
4.
5.
J-8457
J-8458
J-8849
J-9276-2
J-24435-1
thru 7
Bearing
Bearing
Bearing
Bearing
Bushing
C 10, G
Race Installer
Race Installer
Race Installer
Race Installer
Replacement
10-20
6.
7.
8.
9.
10.
11 .
J-8092
J-9519-9
J-9519-7
J-9519-10
J-23028-01
J-23742-1
3-37
Driver Handle
Ball Joint Installer
Ball Joint Remover
&quot;C &quot; Clamp
Spring Remover
Ball Joint Remover
Fig. 50—Special Tools
LIGHT DUTY TRUCK SERVICE MANUAL
3-38
FRONT SUSPENSION
FOUR WHEEL DRIVE (SERIES K10 AND K20)
INDEX
General D escription..........................................................
Front A xle..........................................................................
Transfer Case.....................................................................
Adapter Assembly............................................................
Free Wheeling Hubs.......................................................
Maintenance and Adjustments......................................
Ball Joint Adjustm ent.....................................................
Wheel Bearing A djustm ent...........................................
Component Parts Replacem ent.....................................
Free Wheeling Hubs.......................................................
K-10 Series.......................................................................
K-20 Series.......................................................................
Front Axle Assembly......................................................
3-38
3-38
3-38
3-38
3-38
3-39
3-39
3-48
340
340
340
341
343
Removal..............................................................................
Installation.........................................................................
Disassembly......................................................................
Wheel H ub.....................................................................
Spindle..............................................................................
Axle Joint.........................................................................
Ball Joint Service..........................................................
Assembly............................................................................
Replacement of Knuckle Assembly.......................
Spindle Components....................................................
Wheel Hub Components............................................
Wheel Bearing Adjustment.....................................
Special Tools.........................................................................
343
343
343
343
344
344
346
347
347
348
348
348
349
GENERAL DESCRIPTION
Primary purpose of four wheel drive is to provide
additional tractive effort in off-the-road driving in order
to overcome such obstacles as sand, deep mud or snow,
hilly terrain with steep grades, etc.
With four wheels capable of driving, all the vehicle and
payload weight is utilized to give maximum tire traction.
The power unit is driven through a transmission and
consists of an adapter and a two-speed transfer case with
a steering and driving front axle. A single control lever is
used to shift the transfer case from direct drive to low
four wheel drive at a ratio of 1.94 to 1, thus eight
forward speeds and two in reverse are provided.
Some vehicles (utility with automatic transmission and
eight cylinder engines) are equipped with a new Full
Time 4 wheel drive transfer case see section 7 for further
information.
Front wheel drive may be engaged or disengaged at any
time without clutching when the transfer case is in direct
drive; however, in returning to 2 wheel drive from 4
wheel drive the accelerator may have to be varied as
steady pressure is applied on lever. This releases gear
tooth pressure during shifting.
A yoke and trunnion universal joint permits continuous
power flow to each front wheel, regardless of the turning
angle.
Provisions for Power Take-off have been incorporated in
the transfer case.
FRONT AXLE
The front axle is a hypoid gear axle unit equipped with
steering knuckles. Axle assembly number and production
date are stamped on left tube of assembly. Conventional
truck service brakes are provided on all 4-wheel drive
units.
TRANSFER CASE
The transfer case is basically the devise which controls
the &quot;high&quot; and &quot;low&quot; gear ranges. The shifting into
&quot;low&quot; range also initiates four wheel driving action by
connecting thru the front and rear axles. Four wheel
drive is also possible in the 4-HI range. Utility vehicles
with automatic transmission and eight cylinder engines
are equipped with a new Full Time 4 wheel drive system.
Refer to Section 7 for service procedures.
ADAPTER ASSEMBLY
The adapter assembly is the means of making a
mechanical connection between the transmission and the
transfer case. Different adapters are used dependent
upon the transmission and transfer case with which the
vehicle is equipped. Refer to Section 7 for service
procedures.
FREE WHEELING HUBS (Fig. 51)
Free-wheeling hubs are available for the front wheels of
all four wheel drive vehicles except those equipped with
the new Full Time 4 wheel drive transfer case. The
purpose of these hubs is to reduce friction and wear by
disengaging the front axle shafts, differential and drive
line from the front axle shafts, differential and drive line
from the front wheels when the vehicle is operated under
conditions where front wheel drive is not needed.
The engagement and disengagement of free-wheeling
hubs is a manual operation which must be performed at
each front wheel. The transfer case control lever must be
in 2 -wheel drive position when locking or unlocking
hubs. Both hubs must be in the fully locked or fully
unlocked position. They must not be in the free-wheeling
position when low all wheel drive is used as the
additional torque output in this position can subject the
rear axle to severe strain and rear axle failure may
result.
LIGHT DUTY TRUCK SERVICE MANUAL
FR O N T SU S PEN SIO N
3 -3 9
MAINTENANCE A N D ADJUSTMENTS
BALL JOINT ADJUSTMENT
Front axle ball joint adjustment is generally necessary
only when there is excessive play in steering, irregular
wear on tires or persistent loosening of the tie rod is
observed.
1. Raise vehicle on hoist then place jack stands just
inside of front springs.
2. Disconnect connecting rod and tie rod to allow
independent movement of each steering knuckle.
3. At top of knuckle, apply torque wrench to one of
the steering arms attaching stud nuts, then check
torque necessary to turn the steering knuckle.
Maximum torque should be: 20 ft. lbs. for Axle 44-B
NOTE: Knuckle should tarn smoothly
through turning arc but have no vertical end
play.
BALL STUD ADJUSTING SLEEVE
STEERING ARM
BALL SOCKET
SPINDLE
HUB CAP
DRIVE GEAR
SNAP RING
PRESSURE SPRING
THRUST WASHER
SLINGER
BALL SOCKET
SNAP RING
Fig. 51—Steering Knuckle and Hub Assembly
LIGHT DUTY TRUCK SERVICE MANUAL
3 -4 0 FRONT SU SPEN SION
CO M PO N EN T PARTS REPLACEMENT
FREE-WHEELING HUB
The free wheeling hub assemblies used on the front
wheels are serviceable.
K10 Series (Fig. 54)
Removal (Fig. 52)
1. Turn actuator lever to set hub to “LOCK” position
(fig. 53) and raise vehicle on hoist.
2. Remove six retaining plate bolts and remove
retaining plate actuating knob and “O” ring.
3. Remove internal snap ring, outer clutch retaining
ring and actuating cam body.
4. Relieve pressure on the axle shaft snap ring and
remove snap ring.
5. Remove the axle shaft sleeve and clutch ring
assembly and inner clutch ring and bushing
assembly.
6 . Remove pressure spring and spring retainer plate.
Disassembly
1. Remove actuator knob and “O ” ring from
retaining plate, discard “O” ring and replace with a
new “O ” ring during assembly.
2. Slide inner clutch ring and bushing assembly from
axle sleeve and clutch ring assembly.
Inspection
1. Wash all parts in solvent and air dry.
2. Inspect all parts for wear, cracks or broken teeth.
3. Replace all “O” rings during assembly.
Assembly
Place new “0 ” ring seal on actuator knob. Apply lubri-plate
to “ 0 ” ring and place actuator knob in retaining plate.
Installation
All parts should be lubricated during assembly to
prevent deterioration before the unit is put into service.
1. Install spring retainer plate (flange side facing
bearing) over spindle nuts and seat retainer against
bearing outer cup.
2. Install pressure spring into position. Large O.D.
seats against spring retaining plate.
FREE POSITION
9
8
7
6
5
4
3
1. Spring Retainer Plate
2. Pressure Spring
3. Inner C lutch Ring and
Bushing Assembly
4. A xle Shaft Sleeve and
C lutch Ring Assembly
5. O uter C lutch Retaining Ring
6. Internal Snap
Ring
2
1
7. “ O ” Ring
8. Retaining Plate
9. Retaining Plate Bolts
and Seals
10. A ctu a to r Knob
11. A xle Shaft Snap
Ring
12. “ O ” Ring
13. A ctu a tin g Cam Body
Fig. 52—Hub Assembly — K-10
LOCK POSITION
Fig. 53—Hub Key Position — Typical
LIGHT DUTY TRUCK SERVICE MANUAL
F R ON T S U S PEN SIO N
3.
4.
5.
6.
7.
8.
NOTE: Spring is an interference fit. When
spring is seated, spring extends past the
spindle nuts by approximately 7/8” .
Place inner clutch ring and bushing assembly into
axle shaft sleeve and clutch ring assembly and
install as an assembly onto the axle shaft. Press in
on assembly and install axle shaft snap ring.
NOTE: Install 7/16 x 20 bolt in axle shaft
end and pull outward on axle shaft to aid in
installing snap rings.
Install actuating cam body (cams facing outward),
outer clutch retaining ring and internal snap ring.
Install “O” ring on retaining plate and install
actuating knob and retaining plate.
NOTE: Install actuating knob with knob in
“LOCK” position—grooves in knob must fit
into actuator cam body.
Install six cover bolts and seals.
Turn knob to “FREE” position to check for proper
operation.
Lower vehicle to floor.
FREE-WHEELING HUB
K20 Series (Fig. 54)
Removal
1. Place vehicle on hoist and raise hoist.
2. Turn hub key knob to the “FREE” position.
3. Remove alien head bolts securing the retainer cap
assembly to the wheel hub.
4. Pull off the hub cap assembly and gasket; also
remove exterior sleeve extension housing and
gasket.
Disassembly o f Locking Hub Cap Assembly.
a.
b.
c.
d.
Turn hub key knob to locked position.
Drive out key knob retainer roll pin.
Remove outer clutch gear assembly.
Remove lock ring and remove slotted adjust&shy;
ment sleeve.
e. Remove spring.
f. Remove lock ring securing the plastic key knob
to the hub retainer cap.
g. Remove “O ” ring from the plastic hub key
knob.
5. Remove snap ring from end of axle shaft.
6 . Pull internal clutch gear and collar.
Inspection
1. Discard all seals, gaskets and “O” rings.
2. Wash all parts in solvent and air dry.
3-41
3. Inspect all parts for wear, cracks for broken teeth
and replace as necessary.
4. Replace all seals gaskets and “O” rings.
Installation
1. Install internal clutch gear collar and gear.
2. Install lock ring at end of axle shaft.
3. Assembly of Locking Hub Cap Assembly.
a. Use “O” ring lube and install the new “O ” ring
in the groove of the plastic hub key knob and
insert into retainer cap.
b. Install the lock ring securing the plastic key
knob to the hub retainer cap.
NOTE: Check to see that lock ring is fully
engaged into slot by pushing outward on the
plastic knob.
c. Install the slotted adjustment sleeve with the two
tabs facing downward.
d. Install the key knob retaining roll pin with knob
in “LOCKED” position.
e. Install spring.
f. Place outer clutch gear assembly on top of
spring, compress spring and install lock ring at
sleeve end.
g. Turn key knob to “FREE” position.
NOTE: Before continuing to install the
extension housing and the assembled cap
assembly, remove the head from a 3 /8” bolt
5 inches long and use to align the assembly
of parts to the hub.
4. Install above noted bolt alignment tool into one of
the hub housing bolt holes.
5. Install the new exterior sleeve extension housing
gasket and housing and the new hub retainer cap
assembly gasket and cap assembly.
6 . Install alien head bolts securing the retainer cap
assembly to the wheel hub. Torque to specifications.
7. Turn hub key knob to the locked position to assure
engagement into position.
8 . Install wheel and tire assembly and lower vehicle to
floor.
FRONT AXLE ASSEMBLY (Refer to Fig. 55)
Removal
1. Disconnect propeller shaft from front axle
differential.
2. Raise front of vehicle on hoist until weight is
removed from front springs. Support truck with
jack stands behind front springs.
3. Disconnect connecting rod from steering arm.
4. Disconnect brake hoses from frame fittings and cap
LIGHT DUTY TRUCK SERVICE MANUAL
3 -4 2 FRONT SU SPEN SION
SPRING
RETAINER
PLATE
INNER
CLUTCH RING
AXLE SHAFT
SNAP RING
OUTER CLUTCH
RETAINING
RING
AXLE SHAFT
SLEEVE AND RING
O ” RING
ACTUATING
CAM BODY
ACTUATOR KNOB
“ O &quot; RING
\
WASHER
INTERNAL
SNAP RING
BUSHING
HUB RING
RETAINING KNOB
AXLE SHAFT
SNAP RING
RETAINING
PLATE BOLTS
GEAR HUB
HOUSING
INNER
CLUTCH GEAR
ACTUATING
CAM PIN
\
ACTUATING
KNOB RETAINER
INNER
GASKET
(METAL)
OUTER
RETAINER
GASKET
DISHED
WASHER
RETAINER
SCREWS
ACTUATING
KNOB &quot; O ” RING
^
ACTUATING
KNOB
Fig. 54—Hub Assemblies - Explode
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
3 -4 3
Fig. 55—Front Drive Axle Assembly
5.
6.
7.
8.
all fitting ends or cover with a rag to prevent
contamination.
Disconnect shock absorbers from axle brackets.
Disconnect axle vent tube clip at the differential
housing (see fig. 56).
Dismount “U ” bolts from axle to separate axle
from truck springs.
Raise truck to clear axle assembly and roll front
axle out from under the truck.
Installation
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
steps 3, 5, 6 and 8.
1. Truck should be on jack stands as in Step 2 of
removal instructions.
2. Place axle in position under truck.
3. Install “U ” bolts attaching axle to front springs.
4. Attach shock absorbers to axle brackets.
5. Connect brake hoses to frame fittings bleed the
brake system (see Section 5).
6 . Attach connecting rod to steering arm.
7. Remove jack stands and lower front of truck.
8 . Assemble propeller shaft to front axle differential.
9. Lower vehicle to floor.
Disassembly
NOTE: Refer to K10 or K20 free wheeling
hub for removal of 4-wheel drive units with a
free wheeling hub assembly, before starting
the disassembly of the front axle assembly.
1. Securely mount the axle assembly in a suitable
holding fixture.
2. If the vehicle is not equipped with RPO F76 free&shy;
wheeling hubs, remove the hub cap and snap ring.
3. Remove the drive gear and pressure spring. Place a
hand over the drive gear and use a screwdriver to
pry the gear out.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -4 4 FRONT SU SPEN SION
4. Remove the wheel bearing outer lock nut, lock ring,
and wheel bearing inner adjusting nut using Tool
J-6893 and Adapter J-23446 or tool J-6893-01. (See
fig. 58).
5. Remove the disc assembly, outer wheel bearing and
the spring retainer plate.
NOTE: If the disc or other brake components
require repairs or replacement, refer to
Section 5.
Disassemble Wheel Hub Components (Fig. 57)
a. Remove the oil seal and inner bearing cone
from the hub using a brass drift and tapping
with a hammer. Discard the oil seal.
b. Remove the inner and outer bearing cups using
a brass drift and hammer.
6 . Remove the spindle retaining bolts
7. Remove the spindle and bronze thrust washer by
tapping the end of the spindle lightly with a soft
hammer to break it loose from the knuckle as
shown in Figure 59. Discard the thrust washer if
any wear has occured.
Disassemble Spindle Components:
a. Secure the spindle in a vise by locating on the
high step diameter. Be sure that the machined
surface of the spindle will not be damaged by
the vise jaws.
b. Remove the oil seal.
c. Remove the needle roller bearing.
8 . Remove the axle shaft and joint assembly.
9. Remove axle slingers by placing into a vise and
tapping off as shown in Figure 59 or using a press.
NOTE: If spindle seals will be replaced, also
replace the axle shaft slingers.
Repair The Axle Joint Components:
a. Remove the lock rings after removing pressure
from the trunnion bearings by squeezing the
ends of the bearing in a vise.
b. Support the shaft yoke in a bench vise or on a
short length of pipe.
c. Using a brass drift and a soft hammer, drive on
end of one trunnion bearing just far enough to
drive opposite bearing from yoke.
d. Support the other side of the yoke in the vise
and drive the other bearing out by tapping on
the end of the trunnion using a brass drift.
e. Remove trunnion.
f. Clean and inspect bearings. Lubricate with a
high melting point type wheel bearing grease.
g. Replace trunnion and press new or relubricated
bearings into yoke and over trunnion hubs far
enough to install lock rings.
h. Hold trunnion in one hand and tap yoke lightly
to seat bearings against lock rings.
Fig. 57—Removing Bearing Cups
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT SU S PEN SIO N
Fig. 58—Removing Wheel Bearings
3 -45
Fig. 61—Removing Steering Arm Nuts
10. To remove the tie rod:
a. Remove cotter pins.
b. Loosen tie rod nuts and tap on nut with a soft
hammer to break the studs loose from the
knuckle arm.
c. Remove nuts and disconnect the tie rod.
CAUTION: If it is necessary to remove the
steering arm, discard the three selflocking nuts
(Fig. 61) and replace with new nuts at
assembly.
11. Remove the cotter pin from the upper ball socket
nut.
12. Remove the retaining nuts from the upper and
lower ball sockets as shown in Figure 62.
13. Remove the knuckle assembly from the yoke by
inserting a suitable wedge-shaped tool between the
Fig. 60—Removing Axle Slingers
Fig. 62—Removing Ball Socket Retaining Nut
LIGHT DUTY TRUCK SERVICE MANUAL
3 -4 6 FRONT SU SPEN SION
J -2 3 4 5 4 -1
BALL JOINT
J-23454-2
J-638
FLAT WASHER
(HIDDEN)
J-9519-10
J-9519-10
Fig. 6 3 — R e m o v in g Lower B all J o in t
lower ball stud and the yoke and tapping on the
tool to release the knuckle assembly. Repeat as
required at the upper ball stud location.
Ball Joint Service
CAUTION:
Do not remove the yoke upper ball
stud adjusting sleeve unless new ball studs are
being installed. If it is necessary to loosen the
sleeve to remove the knuckle, do not loosen it
more than two threads using Spanner J-23447
as shown in Figure 67. The nonhardened
threads in the yoke can be easily damaged by
the hardened threads in the adjusting sleeve if
caution is not used during knuckle removal.
NOTE: Remove the lower ball joint snap
ring before beginning.
NOTE: Lower ball joint must be removed
Fig. 6 5 — In s ta llin g Low er B all J o in t
before any service can be performed on the
upper ball joint.
14. Remove the lower ball joint using tools J-9519-10,
J-23454-1, and sleeve J-6382-3 or equivalent as
shown in Figure 63.
NOTE: Tool J-6382-3 is a previously released
transmission tool. If this tool is not available,
a suitable tool may be fabricated from 2
1/2” O.D. steel tubing with 3/16” wall
thickness cut 2 1/ 2 ” long.
15. Remove the upper ball joint using tools J-9519-10,
J-23454-1, and sleeve J-6382-3 or equivalent as
shown in Figure 64.
Assembly
1. Install the lower ball joint into the knuckle. Make
sure that the lower ball joint (the joint without
J -6 3 8 2 -3
/
,
\
A
BALL JO INT M J-? '~ .4 5 4 -2
Fig. 64—Removing Upper Ball Joint
Fig. 66—Installing Upper Ball Joint
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT S U S PEN SIO N
2.
\
3.
4.
5.
cotter pin hole in the stud end) is straight. Press the
stud into the knuckle until properly seated using
tools J-9519-10, J-23454-2, and J-6382-3 or equiva&shy;
lent as shown in Figure 64 and install snap ring.
Install the upper ball joint into the knuckle. Press
the stud into the knuckle until properly seated using
tools J-9519-10, J-23454-2, and J-6382-3 or equiva&shy;
lent as shown in Figure 66 .
Position the knuckle and sockets to the yoke. Install
new nuts finger tight to the upper (the nut with the
cotter pin slot) and lower ball socket studs.
Push up on the knuckle (to keep the ball socket
from turning in the knuckle) while tightening the
lower socket retaining nut. Torque lower nut to 70
ft. lbs.
Torque the yoke upper ball stud adjusting sleeve to
50 ft. lbs. using Spanner J-23447.
6 . Torque the upper ball socket nut to 100 ft. lbs. as
shown in Figure 68 . After torquing the nut, do not
loosen to install cotter pin, apply additional torque,
if necessary, to line up hole in stud with slot in nut.
Replacement of Knuckle Assembly
1.
J-23447
2.
3.
4.
5.
Fig. 67—Loosening Ball Stud Adjusting Sleeve
3 -4 7
6.
NOTE: In the event that knuckles are
received with the sockets and snap ring
assembled, along with the bottom torque
prevailing nut, top castilation nut, split sleeve
and cotter key, it is recommended that after
all of the old parts are removed from the
yoke, the steps listed below are to be followed
for assembly of the knuckle to the yoke:
Assemble knuckle to yoke. Assemble bottom torque
prevailing nut. Torque nut to 70-90 ft. lbs.
NOTE: If the stud turns while attempting to
torque this nut, assemble the top nut and
tighten till it is snug. This will pull the
bottom stud into the tapered hole of the yoke
and will prevent it from turning while
torquing up the nut. After you have applied
the 70-90 ft. lbs. Only use this method when
necessary.
Remove the top nut.
Assemble Sleeve. Torque sleeve to 50 ft. lbs. using
Spanner J-23447.
Assemble top nut. Torque nut to 100 ft. lbs. Tighten
nut to line up the hole of the stud to the next
castilation on slot of the nut.
NOTE: Do not loosen nut to install cotter
pin, apply additional torque, if necessary, to
line up hole in stud with slot in nut.
Assemble cotter key.
Assemble remaining wheel end parts.
If Tie Rod and Steering Arm Were Removed:
Fig. 68—Torquing Upper Ball Socket Nut
a. Assemble the steering arm using the three stud
adapters and three new self-locking nuts.
Torque the nuts to 90 ft. lbs.
b. Assemble the tie rod to the knuckle arm. Torque
the tie rod nuts to 45 ft. lbs. and install cotter
pin.
7. Using the outer wheel bearing spindle nut as an
installer, assemble the inner axle slinger (yoke side)
to the shaft. Place spindle nut in a vise and the
slinger over the end of the shaft. Tap on the end of
the shaft with a soft hammer until the slinger is
fully seated.
8 . Assemble the outer axle slinger (spindle side) to the
shaft using one of the wheel spindles as a starting
guide.
NOTE: Do not use spindle as a pressing or
driving tool. Also, use care not to damage
spindle seal surface on slinger.
LIGHT DUTY TRUCK SERVICE MANUAL
3 -4 8 FRONT SU S PEN SIO N
Assemble Spindle Components:
a. Place the spindle in a vise on the high step and
install needle roller bearing using Installer
J-23445 and Drive Handle J-8092.
b. Install grease seal onto slinger with lip toward
spindle.
c. Relubricate the needle bearing and the spindle
end (Fig. 69) with a high melting point type
wheel bearing grease.
9. Assemble axle shaft and joint assembly (see “To
repair the axle joint components” on Page 3-) and
install in housing.
10. Install the bronze thrust washer over the axle shaft
with the chamfer toward the slinger and install the
spindle as shown in Figure 69.
11. Assemble spindle to knuckle.
NOTE: Torque spindle nuts to 45 ft. lbs.
lbs. (while rotating hub) to seat the bearings using
Tool J-6893 and Adapter J-23446 or J-6893-01. Back
off the inner adjusting nut and retorque to 35 ft.
lbs. while the hub is being rotated.
13. Back off the inner adjusting nut again 1/4 turn
maximum. Assemble lockwasher by turning nut to
nearest hole in lockwasher. Install outer lock nut
and torque to 50 ft. lbs. (minimum).
NOTE: Hub assembly should have .001 to
.010 inch end play.
14. If vehicle is not equipped with free-wheeling hubs,
install the hub cap assembly. If the vehicle is
equipped with free-wheeling hubs, refer to free&shy;
wheeling hub assembly and installation procedures.
ASSEMBLE WHEEL HUB COMPONENTS
(Wheel Bearing Adjustment)
a. Assemble the outer wheel bearing cup into the
wheel hub using Installer J-6368 and Driver
Handle J-8092.
b. Assemble the inner wheel bearing cup into the
wheel hub using Installer J-23448 and Driver
Handle J-8092.
c. Pack the wheel bearing cone with a high melting
point type wheel bearing grease and insert the
cone into the cup.
12. Install the disc and the outer wheel bearing cone to
the spindle. Torque the inner adjusting nut to 50 ft.
Fig. 69—Installing Spindle and Thrust Washer
LIGHT DUTY TRUCK SERVICE MANUAL
FRONT S U S PEN SIO N
3 -4 9
SPECIAL TOOLS
1.
2.
3.
4.
5.
J-6368
J-6893-01
J-8092
J-9519
J-23445
Bearing Race Installer
Bearing Installer
Driver Handle
“ C &quot; Clamp
Bearing Installer
6.
7.
8.
9.
10.
J-6382-3
J-23447
J-2 3448
J-23454-1
J-23454-2
Sleeve
Adjusting Sleeve Spanner
Cup and Seal Installer
Ball Joint Remover/Installer
Ball Joint Remover/Installer
Fig. 70—Special Tools — 4 Wheel Drive
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
4-1
SECTION 4
REAR SUSPENSION AND DRIVELINE
The following caution applies to one or more steps in the assembly
procedure of components in this portion of the manual as indicated at
appropriate locations by the terminology &quot;See Caution on page 1 of this
Section&quot;.
CAUTION: THIS FASTENER IS A N IMPORTANT ATTACHING PART IN
THAT IT COULD AFFECT THE PERFORMANCE OF VITAL COMPO&shy;
NENTS AND SYSTEMS, AND/OR COULD RESULT IN MAJOR REPAIR
EXPENSE. IT MUST BE REPLACED WITH ONE OF THE SAME PART
NUMBER OR WITH A N EQUIVALENT PART IF REPLACEMENT
BECOMES NECESSARY. DO NOT USE A REPLACEMENT PART OF
LESSER QUALITY OR SUBSTITUTE DESIGN. TORQUE VALUES MUST
BE USED AS SPECIFIED DURING REASSEMBLY TO ASSURE PROPER
RETENTION OF THIS PAR T.
CONTENTS OF THIS SECTION
4-1
4-8
4-16
Rear Suspension
Propeller Shaft...
Rear Axle...........
REAR SUSPENSION
INDEX
4-1
4-2
4-2
4-3
4-4
4-7
4-7
General Description
Component Parts Replacement
Shock Absorbers.......................
Stabilizer Shaft.........................
Leaf Spring Assembly...........
Shackles and Hangers
U-Bolts
GENERAL DESCRIPTION
All 10-30 series vehicles use a leaf spring/solid rear axle
suspension system. Typical systems are illustrated in
figures 1, 2 and 3.
The rear axle assembly is attached to multi-leaf springs
by &quot;U &quot; bolts. The spring front eyes are attached to the
frame at the front hangers, through rubber bushings.
The rear ends of the springs are attached to the frame
by the use of shackles which allow the spring to &quot;change
its length&quot; while the vehicle is in motion. Control arms
are not used with leaf springs.
Ride control is provided by two identical direct double
acting shock absorbers angel-mounted between the
frame and brackets attached to the axle tubes.
Fig. 1—Typical C-K Truck Rear Suspension
LIGHT DUTY TRUCK SERVICE MANUAL
4 -2 REAR SU S PEN SIO N AND DRIVELINE
Fig. 2—Typical G-Truck Rear Suspension
CO M PO N EN T P/
SHOCK ABSORBERS
Replacement
Refer to figures 4, 5, 6 , 7 and 8 for specific vehicle
mounting provisions.
1. Raise vehicle on hoist, and support rear axle.
2. If equipped with air lift shock absorbers, bleed air
from lines. Disconnect line from shock absorber.
3. At the upper mounting location, disconnect shock
absorber by removing nut and washers shown, and
bolt on G-models.
4. At the lower mounting location, remove nut,
washers and bolt as shown.
REPLACEMENT
5. Remove shock absorber from vehicle.
6 . To install shock absorber, place into position and
reattach at upper mounting location. Be sure to
install nuts and washers as shown.
7. Align lower end of shock absorber with axle
bracket, and install bolt, washers and nut, as shown.
8 . Tighten nuts to specifications.
CAUTION: See CAUTION on page 1 of this
section, regarding shock absorberfasteners.
9. If equipped with airlift shock absorbers, inflate to
10-15 pounds minimum air pressure.
10. Lower vehicle and remove from hoist.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S P E N S IO N A N D DRIVELINE
4-3
Fig. 6—Shock Absorber—G-10, 20, 30
STABILIZER SHAFTS
Refer to figures 9, 10 and 11 for specific rear stabilizer
shaft mounting on C and P models.
Replacement
1. Raise vehicle on hoist and support rear axle.
2. Remove nut, washer and grommet from link bolt at
the frame side member on each side.
3. Withdraw link bolt, washers, grommets and spacer.
4. Remove brackets from anchor plates by removing
attaching screws.
5. Remove stabilizer shafts.
6 . Reverse above steps to install stabilizer shaft. On
installation, position shaft so parking brake cable is
routed over stabilizer.
7. Torque all bolts to specifications.
CAUTION: See CAUTION on page 1 of this
section, regarding stabilizerfasteners.
8 . Lower hoist and remove vehicle.
LIGHT DUTY TRUCK SERVICE MANUAL
4 -4 REAR SU S PEN SIO N AND DRIVELINE
‘ NOTE: Torque nut by running
nut to unthreaded portion
of link bolt.
Fig. 10—Rear Stabilizer Shaft—C-20(63), C-30
LEAF SPRING ASSEMBLY
Refer to figures 12, 13, 14 and 15 for specific leaf spring
mounting provisions of C, K, G and P models. Figure 17
illustrates a typical U-bolt anchor plate installation with
the mandatory tightening sequence.
CAUTION: See CAUTION on page 1 of this
section, regarding leafspringfasteners.
Removal
1. Raise vehicle on hoist so that tension in spring is
relieved.
Fig. 11—Rear Stabilizer Shaft—P-30
2. Loosen, but do not remove, spring-to-shackle
retaining nut.
3. Remove nut and bolt securing shackle to spring
hanger.
4. Remove nut and bolt securing spring to front
hanger.
5. Remove &quot;U &quot; bolt retaining nuts, withdraw &quot;U &quot;
bolts and spring plate from spring-to-axle housing
attachment.
6 . Withdraw spring from vehicle.
7. Inspect spring. Replace bushings, repair or replace
spring unit as outlined in this section.
Fig. 12—Rear Spring I nstallation—G Models
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S P E N S IO N A N D DRIVELINE
4-5
Fig. 13—Rear Spring Installation—C-K Models
LIGHT DUTY TRUCK SERVICE MANUAL
4 -6 REAR S U S PEN SIO N AND DRIVELINE
Fig. 15—Rear Spring Installation—P30
Bushing Replacement
1. Place spring on press and press out bushing using a
suitable rod, pipe or tool as shown in figure 16.
2. Press in new bushing; assure that tool presses on
steel outer shell of bushing.
Fig. 16—Pressing Out Bushing
Spring Leaf Replacement
1. Place spring assembly in a bench mounted vise and
remove spring clips.
2. Position spring in vise jaws, compressing leaves at
center and adjacent to center bolt.
3. File peened end of center bolt and remove nut.
Open vise slowly to allow spring assembly to
expand.
4. Wire brush and clean spring leaves. Inspect spring
leaves to determine if replacement is required; also
replace defective spring leaf liners at this time.
5. Align center holes in spring leaves by means of a
long drift and compress spring leaves in a vise.
6 . Remove drift from center hole and install a new
center bolt. Peen bolt to retain nut.
7. Align spring leaves by tapping with hammer, then
bend spring clips into place or install bolts and
spacer if so equipped.
NOTE: Spring clips should be bent suffi&shy;
ciently to maintain alignment, but not tight
enough to bind spring action.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR SU S PEN SIO N A N D DRIVELINE
Leaf Spring Installation
4-7
SHACKLE REPLACEMENT
1. Position spring assembly to axle. Make sure spring
is in position at both spring hangers.
NOTE: The shackle assembly must be
attached to the rear spring eye before
installing shackle to rear hanger.
2. Install spring retainer plate and &quot;U &quot; bolts. Loosely
install retaining nuts, but do not torque at this time.
3. Jack frame as required to align spring and shackle
with spring hangers.
4. Install shackle bolt and nut and again reposition
spring, if necessary to align front eye. Install front
eye bolt and nut.
5. Lower vehicle so that weight of vehicle is on
suspension components and torque affected suspen&shy;
sion parts to specifications.
6 . Lower vehicle and remove from hoist.
1. Raise vehicle on hoist. Place adjustable lifting
device under axle.
2. Remove load from spring by jacking frame.
3. Loosen spring-to-shackle retaining bolt, but do not
remove.
4. Remove shackle-to-frame bracket retaining b o ltthen remove shackle bolt from spring eye.
5. Position shackle to spring eye and loosely install
retaining bolt—do not troque retaining bolt at this
time.
6 . Position shackle to frame bracket and install
retaining bolt.
7. Rest vehicle weight on suspension components and
torque both shackle bolt retaining nuts to
specifications.
CAUTION: See CAUTION on page 1 of this
section, regarding thesefasteners.
U-Bolt and Anchor Plate Installation
Figure 17 illustrates the m andatory sequence of
tightening U-bolt nuts. Tighten diagonally opposite nuts
to 40-50 foot pounds, then tighten all nuts as shown to
specifications.
CAUTION: See CAUTION on page 1 of this
8 . Lower vehicle and remove from hoist.
section, regarding &quot;U&quot;-Boltfasteners.
Fig. 17—Typical U-Bolt Installation
LIGHT DUTY TRUCK SERVICE MANUAL
4 -8 REAR S U S PEN SIO N AND DRIVELINE
PROPELLER SHAFT
INDEX
Theory of Operation...................
Component Parts Replacement
THEORY OF OPERATION
Universal Joints
The simple universal joint is basically two Y-shaped
yokes connected by a crossmember called a spider. The
spider is shaped like an X and arms that extend from it
are called trunnions. See figure 18.
The spider allows the two yoke shafts to operate at an
angle to each other. When torque is transmitted at an
angle, through this type of joint, the driving yoke rotates
at a constant speed while the driven yoke speeds up and
slows down twice per revolution. This changing of
velocity (acceleration) of the driven yoke increases as the
angle between the two yoke shafts increases. This is the
prime reason why single universal joints are not used for
angles greater than three to four degrees. At four
degrees, for example the change of velocity is .5%. At ten
degrees it is 3%. If the universal joint were set at 30
degrees and the driving yoke were turning at 1000 RPM
the velocity of the driven yoke would change from 856
RPM to 1155 RPM in one quarter of a revolution. In the
remaining quarter revolution the velocity would change
from 1155 RPM to 866 RPM.
On a one-piece drive shaft this problem can be
eliminated by arranging two simple universal joints so
that the two driving yokes are rotated 90 degrees to each
other. However the angle between the drive and driven
yokes must be very nearly the same on both joints for
this to work. Refer to figure 19. This allows the alternate
acceleration and deceleration of one joint to be offset by
Fig. 18—Simple Universal Joint
............................................. 4-8
............................................. 4-9
the alternate deceleration and acceleration of the second
joint. When the two joints do not run at approximately
the same angle, operation can be rough and an
objectionable vibration can be produced.
Universal joints are designed to consider the elfects of
various loadings and rear axle windup, during accelera&shy;
tion. Within the design angle variations the universal
joints will operate safely and efficiently. However, when
the design angles are exceeded the operational life of the
joints may decrease.
The bearings used in universal joints are the needle
roller type. The needle rollers are held in place on the
trunnion by round bearing cups. The bearing cups are
held in the yoke by either (depending on the
manufacturer) snap rings or plastic injection. These
joints usually are lubricated for life and cannot be
lubricated while on the vehicle.
Constant Velocity Joint—Double Cardan
Joint
As mentioned previously, the simple universal joint will
operate efficiently through small angles only. Also, two
simple universal joints phased properly and operating
through the same angle will transmit constant velocity.
When a large angle is encountered in a driveline, a
simple universal joint will introduce two vibrations in
each revolution. It is in this situation that a constant
velocity joint is used.
Essentially, the constant velocity joint is two simple
universal joints closely coupled by a coupling yoke,
phased properly for constant velocity.
A centering ball socket between the joints maintains the
relative position of the two units. This centering device
causes each of the two units to operate through one-half
of the complete angle between the drive shaft and
differential carrier. See figure 20.
Fig. 19—Universal Joints Arranged for Constant
Velocity
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
4 -9
length, diameter and the type of splined yoke. On some
models the drive shaft is made up of concentric steel
tubes with rubber elements between.
Each shaft is installed in the same manner. A universal
joint and splined slip yoke are located at the
transmission end of the shaft, where they are held in
alignment by a bushing in the transmission rear
extension. The slip yoke permits fore and aft movement
of the drive shaft as the differential assembly moves up
and down. The spline is lubricated internally by
transmission lubricant or grease. An oil seal at the
transmission prevents leakage and protects the slip yoke
from dust, dirt and other harmful material.
Since the drive shaft is a balanced unit, it should be kept
completely free of undercoating and other foreign
material which would upset shaft balance.
SERVICE INFORMATION
NOTE: The ball/socket on this Constant
Velocity joint requires periodic lubrication. A
lubrication fitting is provided for this
purpose, and is illustrated later in this
section.
Propeller Shafts
The propeller shaft is a steel tube which is used to
transmit power from the transmission output shaft to the
differential. To accommodate various model, wheelbase
and transmission combinations, drive shafts differ in
Both one piece and two piece propeller shafts are used
depending on the model. All are tubular and use needle
bearing type universal joints.
On models that use a two piece shaft, the shaft is
supported near its splined end in a rubber cushioned ball
bearing which is mounted in a bracket attached to a
frame crossmember. The ball bearing is permanently
lubricated and sealed.
Four wheel drive models use a front propeller shaft
incorporating a constant velocity joint, shown in figure
30.
C O M PO N EN T PART REPLACEMENT
PROPELLER SHAFT
Two methods are used to retain the propeller shaft to the
differential pinion flange. One method utilizes &quot;U &quot; bolts,
and the other is a strap attachment. Refer to figures 21
and 22 .
Fig. 21—U-Bolt Attachment
LIGHT DUTY TRUCK SERVICE MANUAL
4 - 1 0 REAR SU S PEN SIO N A ND DRIVELINE
Removal
1. Raise vehicle on hoist. Mark relationship of shaft
to companion flange and disconnect the rear
universal joint by removing trunnion bearing &quot;U &quot;
bolts or straps. Tape bearing cups to trunnion to
prevent dropping and loss of bearing rollers.
2. For models with two-piece shafts remove bolts
retaining bearing support to frame crossmember.
3. Slide propeller shaft forward disengaging trunnion
from axle flange, then slide assembly rearward
disengaging from transmission.
Repairs (Universal Joints)
1.
2.
3.
4.
NOTE: The universal joints are of the
extended-life design. and do not require
periodic inspection or lubrication; however,
when these joints are disassembled, repack
bearings and lubricate reservoir at end of
trunnions with high-melting point wheel
bearing lubricant and replace the dust seals.
Remove bearing lock rings from trunnion yoke.
Support trunnion yoke on a piece of 1-1/4&quot; I.D.
pipe on an arbor bed.
NOTE: Due to length of the propeller shaft it
may be more convenient to use a bench vise,
for removal and installation, instead of an
arbor press. In this case, proceed with
disassembly and assembly procedure as with
an arbor press.
Using a suitable socket or rod, press on trunnion
until bearing cup is almost out. Grasp cup in vise
and work cup out of yoke.
NOTE: The bearing cup cannot be fully
pressed out.
Press trunnion in opposite direction and remove
other cup as in Step 3.
Fig. 24—Bearing Cup Removal with Press
Clean and inspect dust seals, bearing rollers, and
trunnion. Relubricate bearings as indicated in
Section 0.
NOTE: In addition to packing the bearings,
make sure that the lubricant reservoir at the
end of each trunnion is completely filled with
lubricant. In filling these reservoirs, pack
lubricant into the hole so as to fill from the
bottom (use of squeeze bottle is recommen&shy;
ded). This will prevent air pockets and ensure
an adequate supply of lubricant.
If not installing a &quot;U &quot; joint service kit, as shown in
figure 25, place dust seals on trunnions with the
cavity of seal toward end of trunnion. Press seal
onto trunnion exercising caution during installation
to prevent seal distortion and to assure proper
seating of seal on trunnion.
NOTE: If installing seal on small size
trunnion, seal installer J-21548 should be
used, shown in figure 26.
Position trunnion into yoke. Paritally install one
bearing cup into yoke. Start trunnion into bearing
cup. Partially install other cup. Align trunnion into
cup, and press cups into yoke. Install lock rings.
1. Trunnion
2. Seal
3. Bearings
Fig. 23—Bearing Cup Removal with Vise
4. Cap
5. Snap Ring
Fig. 25—Universal Joint Repair Kit
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
4-11
CENTER SUPPORT BEARING—FIG. 27
CAUTION: See CAUTION on page 1 of this
section regarding Center Support Bearing
fasteners.
Fig. 26—Trunnion Seal Installer
1. Remove dust shield.
2. Remove strap retaining rubber cushion from
bearing support.
3. Pull support bracket from rubber cushion and pull
cushion from bearing.
4. Pull bearing assembly from shaft.
5. Assemble bearing support as follows:
a. Install inner deflector on propeller shaft, if
removed, and prick punch deflector at two
opposite points to make sure it is tight on shaft.
b. Fill space between inner dust shield and bearing
with lithium soap grease.
Fig. 27—Propeller Shaft, Universal Joint and Bearing Support
LIGHT DUTY TRUCK SERVICE MANUAL
4 -1 2 REAR SU S PEN SIO N A ND DRIVELINE
c. Start bearing and slinger assembly straight on
shaft journal. Support propeller shaft and, using
suitable length of pipe over splined end of shaft,
press bearing and inner slinger against shoulder
on shaft.
d. Install dust shield over shaft, small diameter
first and press into position against outer
slinger.
e. Install rubber cushion onto bearing.
f. Install bracket onto cushion.
g. Install retaining strap.
ALIGNMENT
Installation
1. For models with one piece propeller shafts, slide
shaft into transmission and attach rear U-joint axle.
Torque bolts to specifications.
2. For C-K models with two-piece propeller shafts,
phasing is no longer required due to the alignment
key, shown in figure 28.
3. For G-P models with two piece shafts, install front
half into transm ission and bolt support to
crossmember.
a. Slide grease cap and gasket onto rear splines.
b. Rotate shaft so front U-joint trunnion is in a
vertical position. See figure 29.
c. Take rear propeller shaft and before installing,
align U-joint trunnions in same vertical position
as in step b (at this point all U-joint trunnions
Fig. 28—C-K Propeller Shaft Alignment Key
should be vertical). Then, note relationship of
front shaft and rear shaft spline position. Rotate
rear shaft four splines toward left side of
vehicle, and install rear shaft to front shaft.
Attach rear U-joint to axle. Tighten grease cap.
d. Torque bearing support to crossmember and
U-joint to axle attachments to specifications.
CONSTANT VELOCITY UNIVERSAL JOINT
Disassembly
1. Remove front propeller shaft from vehicle.
FRONT YOKE OF
REAR PROP SHAFT
FRONT
PROP SHAFT
ROTATE
TOW ARD LEFT
SIDE OF VEHICLE
Fig. 29—Aligning U-Joints—G-P Models
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
4 -1 3
8 . Remove front trunnion from center and front yoke
in same manner as described in Steps 2, 3 and 4.
NOTE: Before front trunnion can be
removed all four (4) bearing caps must be
removed.
Assembly
Fig. 30—Driving Out Bearing Cups
2. Remove rear trunnion snap rings from center yoke.
Remove grease fitting.
3. Place propeller shaft in vice as shown in figure 30.
Drive one rear trunnion bearing cap from center
yoke as shown in figure 30 until it protrudes
approximately 3/8&quot;.
4. Once the bearing cup protrudes 3/8&quot;, release vice.
Grasp protruding portion of cup in vice and strike
center yoke as shown in Figure 31 until cup is
removed. Remove cup seal by prying off with a thin
screwdriver.
5. Repeat steps 3 and 4 for remaining bearing cup.
6 . Once the center yoke cups have been removed,
remove rear yoke half bearing cups. Remove rear
trunnion.
7. Gently pull rear yoke half from prop shaft.
Remove all loose needle bearings. Remove spring
seal.
1. Clean and inspect all needle bearings, cups, seals,
fittings, trunnions and yokes. Assemble all needle
bearings in caps (27 per cap); assemble needle
bearings in front yoke (28 total). Retain bearings
with a heavy grease. Assemble seals to bearing
cups.
2. Place front trunnion in drive shaft. Place center
yoke on front trunnion. Install one bearing cup and
seal assembly in front yoke. Drive in to a depth
that the snap ring can be installed. Install snap ring.
Install remaining cup and seal in front yoke. Install
snap ring.
3. Install front trunnion bearing cups in center yoke in
same manner.
4. With front trunnion completely installed, install
seal on prop shaft (large face first). Gently slip rear
yoke half on prop shaft using care not to upset
rollers. Insert rear trunnion in center yoke. Install
rear yoke half bearing caps on rear trunnion. Install
one rear trunnion bearing cap in center yoke and
press into yoke until snap ring can be installed.
Install remaining cap and snap ring.
5. Grease universal as outlined in Section 0 at all
three (3) fittings (2 conventional type and one in
rear yoke half) that requires a needle nose grease
gun adapter.
6 . Install propeller shaft with constant velocity joint
next to transfer case. Torque U-bolts to specifica&shy;
tions. The lubrication fitting at this location is
shown in figure 32.
LUBE FITTING
Fig. 31—Bearing Cup Removal
Fig. 32—Lubrication Fitting
LIGHT DUTY TRUCK SERVICE MANUAL
4 - 1 4 REAR SU SPEN SION AND DRIVELINE
PROPELLER SHAFT A N D UNIVERSAL JO IN T D IA G N O S IS
Checking and Correcting
Propeller Shaft Unbalance—Vehicles with
8-7/8&quot; Ring Gear Differentials Only
1. Place vehicle on a twin post hoist so that the rear
wheels are free to rotate.
2. Remove both rear tire and wheel assemblies and
brake drums.
CAUTION: Use care not to apply brakes with
drums removed.
3. With vehicle running in gear at the indicated speed
where disturbance is at its peak, observe the
intensity of the disturbance.
4. Stop engine and check for any mud or undercoat&shy;
ing on the propeller shaft. If any is found, remove
it and again check the intensity of the vibration. If
vibration is still present, proceed to step 5.
5. Bring indicated speed up to the point where
disturbance was at its peak on the road test and
observe the intensity of the disturbance. Stop
engine and disconnect drive shaft from companion
flange. Reinstall shaft by rotating it 180&deg; from its
original position. Determine which position of the
companion flange gives the best balance.
6 . Install rear drums and wheels, and road test vehicle
for final check of balance. If balance is still
unacceptable, replace drive shaft.
DIAGNOSTIC CHART
COMPLAINT
Leak at front slip yoke.
NOTE: An occasional drop of
lubricant leaking from splined
yoke is normal and requires no
attention.
POSSIBLE CAUSE
a. Rough outside surface on splined
yoke.
b. Defective transmission rear oil
seal.
CORRECTION
a. Replace seal if cut by burrs on yoke.
Minor burrs can be smoothed by careful
use of crocus cloth or honing with a
fine stone. Replace yoke if outside
surface is rough or burred badly.
b. Replace transmission rear oil seal.
c. Bring transmission oil up to proper
level after correction.
Knock in drive line, clunking
noise when car is operated
under floating condition at
10 mph in high gear or
neutral.
a. Worn or damaged universal
joints.
b. Size gear hub counterbore in
differential worn oversize.
a. Disassemble universal joints, inspect
and replace worn or damaged parts.
b. Replace differential case and/or side
gears as required.
Ping, Snap or Click in drive
line.
a. Loose upper or lower control
arm bushing bolts.
a. Tighten bolts to specified torque.
NOTE: Usually occurs on
initial load application after
transmission has been put
into gear, either forward or
reverse.
b. Loose companion flange.
b. Remove companion flange, turn 180&deg;
from its original position, apply white
lead to splines and reinstall. Tighten
pinion nut to specified torque.
Fig. 33A—Diagnosis Chart A
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S P E N S IO N A N D DRIVELINE
COMPLAINT
Roughness, Vibration or
Body Boom at any speed.
NOTE: With tachometer
installed in car, determine
whether propeller shaft is
cause of complaint by
driving through speed range
and note the engine speed
(rpm) at which vibration
(roughness) is most
pronounced. Then, shift
transmission to a different
gear range and drive car at
same engine speed (rpm)
at which vibration was
noted before. Note the
effect on the vibration.
If vibration occurs at the
same engine speed (rpm),
regardless of transmission
gear range selected, drive
shaft assembly is not at
fault, since the shaft
speed (rpm) varies.
If vibration decreased, or
is eliminated, in a
different gear range but
at the same engine speed
(rpm), check the
possible causes:
POSSIBLE CAUSE
4 -1 5
CORRECTION
a. Bent or dented drive shaft.
a. Replace.
b. Undercoating on drive shaft.
b. Clean drive shaft.
c. Tire unbalance. (30-80 mph, not
throttle conscious)
c. Balance or replace as required.
d. Excessive U-bolt torque.
d. Check and correct to specified torque.
e. Tight universal joints.
e. Impact yokes with a hammer to free
up. Overhaul joint if unable to free up
or if joint feels rough when rotated by
hand.
f. Worn universal joints.
f. Overhaul, replacing necessary parts.
g. Burrs or gouges on
companion flange. Check
snap ring locating surfaces
on flange yoke.
g. Rework or replace companion flange.
h. Drive shaft or companion
flange unbalance.
h. Check for missing balance weights
on drive shaft. Remove and
reassemble drive shaft to companion
flange, 180&deg; from original position.
i. Excessive looseness at slip
yoke spline.
i. Replace necessary parts.
j. Drive shaft runout (50-80 mph
throttle conscious)
j. Check drive shaft runout at front and
rear. Should be less than specified. If
above, rotate shaft 180&deg; and recheck.
If still above specified, replace shaft.
Roughness usually at low speeds,
light load, 15-35 mph.
a. U-bolt clamp nuts excessively
tight.
a. Check and correct torque to that
specified. If torque was excessive
or if brenelled pattern on trunnions
is evident, replace joints.
Scraping noise.
a. Slinger, companion flange, or
end yoke rubbing on rear axle
carrier.
a. Straighten slinger to remove
interference.
Roughness on heavy
acceleration (short duration.)
a. Double cardan joint ball seats
worn. Ball seat spring may be
broken.
a. Replace joint and shaft assembly.
Roughness -- above 35 mph
felt and/or heard.
a. Tires unbalanced or worn.
a. Balance or replace as required.
Fig. 33B—Diagnosis Chart B
LIGHT DUTY TRUCK SERVICE MANUAL
4 -1 6 REAR SU S PEN SIO N A N D DRIVELINE
REAR AXLE
INDEX
General Description..........................................................
Theory of Operation.........................................................
Component Parts Replacem ent.....................................
8-7/8&quot; Ring Gear A xle...............................................
Axle Assembly.............................................................
Axle Shaft.....................................................................
Pinion Oil Seal...........................................................
4-16
4-20
4-25
4-25
4-25
4-25
4_27
10-1/2&quot; and 12-1/4&quot; Ring G ear..............................
Axle Assembly.............................................................
Axle Shaft.....................................................................
Axle V ent......................................................................
Hub and Drum Assembly.......................................
Bearing Adjustment....................................................
Pinion Oil Seal............................................................
4-29
4-29
4-29
4,29
4.30
4.34
4-34
GENERAL DESCRIPTION
Four distinct axles compromise the truck line-up. These four, categorized by ring gear diameter, are a) 8-7/8&quot;
Ring Gear, b) 10-1/2&quot; Ring Gear, c) Dana 10-1/2&quot; Ring Gear, and 12-1/4&quot; Ring Gear.
Fig. 34—8-7/8&quot; Ring Gear Axle Cross-Section
8 7 /8 &quot; Ring Gear Axle
The axle shown in figure 34 is a semifloating, fabricated
constructed type consisting of a cast carrier with large
bosses on each end into which two welded steel tubes are
fitted. The carrier contains an overhung hypoid pinion
and ring gear. The differential is a two pinion
arrangement.
The axle housing is made up of two steel welded tubes
pressed into the crossbore of the cast carrier. Each tube is
puddle welded to the carrier. Welded-on brackets provide
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
1.
2
.
3.
4.
5.
6.
7.
8.
9.
Companion Flange
Oil Deflector
Oil Seal
Bearing Retainer
Shim
Pinion Front Bearing
Collapsible Spacer
Pinion Rear Bearing
Drive Pinion
10.
11.
12.
13.
14.
15.
16.
17.
18.
Straddle Bearing
R ing Gear
D ifferential Spider
D ifferential Case
Differential Pinion
D ifferential Side Gear
Side Bearing
Side Bearing Adjusting Nut
Adjusting Nut Retainer
19.
20.
21.
22.
23.
24.
25.
4 -1 7
Retainer Screw
Bearing Cap
Case-to-Ring Gear Bolt
Differential Cover
Bearing Cap Bolt
Cover Screw
Axle Shaft
Fig. 35—10-1/2&quot; Ring Gear Axle Cross-Section
attachment points for suspension components such as shock
absorbers and leaf springs. A welded flange is provided for
brake flange plate attachment.
An overhung hypoid drive pinion is supported by two
preloaded tapered roller bearings. The pinion shaft is
sealed by means of a molded, spring loaded, rubber seal.
The seal is mounted on the pinion flange which is
splined and bolted to the hypoid pinion shaft.
The hypoid ring gear is bolted to a one-piece differential
case which is supported by two preloaded tapered roller
bearings.
10-1/2&quot; Ring Gear Axle
The axle shown in figure 35 is of the full floating type
with hypoid ring gear and drive pinion. The full floating
construction enables easy removal of axle shafts without
removing truck load and without jacking up the axle.
The differential carrier is heavily ribbed to provide rigid
support for the differential assembly. Differential caps
are doweled to the carrier to assure correct alignment.
The straddle-mounted drive pinion is supported at the
front by two opposed tapered roller bearings. The pinion
straddle bearing is a roller bearing assembly consisting
of an outer race and roller assembly. A precision ground
diam eter on the pinion pilot functions as an inner race.
Side bearing preload and ring gear-to-pinion backlash
are controlled by side bearing adjusting rings threaded
into the carrier near the axle tubes. Pinion depth is
controlled by a shim located between the pinion bearing
retainer assembly and the axle housing.
LIGHT DUTY TRUCK SERVICE MANUAL
4 -1 8 REAR SU S PEN SIO N AND DRIVELINE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
P in io n N u t
W asher
C o m p a n io n F lange
O il Seal
O il S lin g e r
P in io n F r o n t B e a rin g
F r o n t B e a rin g C u p
P re lo a d S h im Pack
P in io n D e p th S h im Pack
Rear B e a rin g C u p
11.
12.
13.
14.
15.
16.
17.
18.
19.
20 .
P in io n R e ar B e a rin g
D riv e P in io n
R in g G ear
D iffe r e n tia l Case
R in g G ear B o lt
D iffe r e n tia l S ide B e a rin g
S ide B e a rin g C u p
S ide B e a rin g A d ju s tin g S h im s
B e a rin g Cap
B e a rin g C ap B o lt
21.
22.
23.
24.
25
26.
27.
28.
29.
D iff e r e n t ia l S p id e r
D iff e r e n t ia l S id e G ear
W asher
P in io n G ear
W asher
G asket
C o ver
C o v e r S c re w
D ra in P lu g
Fig. 36—Dana 10-1/2&quot; Ring Gear Axle Exploded View
Dana 10*1/2&quot; Ring Gear Axle
The Dana axle shown in figure 36 is a Salisbury-type
similar in design to the 8-7/8&quot; ring gear axle in figure
34. It does differ in several points, however. The axle
shafts are full floating; the carrier must be spread to
remove the differential; and the drive pinion incorpo&shy;
rates two shim packs. The inner pack controls pinion
depth, while the outer pack controls pinion bearing
preload.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S P E N S IO N A N D DRIVELINE
4-19
Fig. 37— 12-1/4&quot; Ring Gear Axle—11,000# Capacity
12-1/4&quot; Ring Gear Axle
(11,000 Pound Capacity)
The 11,000 lb. capacity, single-speed hypoid axle,
illustrated in figure 37, has a straddle mounted drive
pinion which is supported at the rear by a straight roller
bearing. The pinion front bearing consists of a double
row ball bearing.
The differential is a conventional four-pinion type.
Thrust washers are used between the side gears and case
and also between differential pinions and the differential
case.
A thrust pad mounted on the end of an adjusting screw
threaded into the carrier housing limits deflection of the
ring gear under high torque conditions.
Involute splines are incorporated in the axle shaft flange
and in the wheel hubs. This design provides for the
driving torque to be transmitted from the axle shaft to
the hub through the mating splines.
LIGHT DUTY TRUCK SERVICE MANUAL
4 -2 0 REAR S U S PEN SIO N A N D DRIVELINE
THEORY OF OPERATIONSTANDARD DIFFERENTIAL
The differential has two basic functions. First, it
transmits torque from the propeller shaft, through a 90&deg;
turn, to the rear wheels. Second, it takes the torque
provided by the propeller shaft and divides this torque
as necessary to allow each wheel enough torque to rotate
as conditions require.
Gears
The rear axle transmits power through a 90&deg; turn. To do
this, bevel gears as shown in figure 38 were previously
used. Straight bevel and spiral bevel gears were used for
the ring and pinion gears; but the drive and driven gear
center line must intersect, or meet, each other. This is
satisfactory for differential side gears, but, the desire to
lower the driveshaft brought about another variation of
the bevel gear—the hypoid gear, shown in figure 39.
Meshing hypoid gears do not require a meeting of their
center lines. The drive pinion gear may then be placed
below the centerline of the ring gear, thereby lowering
the drive shaft.
Gear Ratio
The drive axle of a vehicle is said to have a certain axle
ratio. Most people are aware of this term, and are
familiar with the ratios most frequently used on specific
vehicles.
At this time, let’s look into the what, how, and why of
axle ratios. W hat is a ratio? How is it achieved? Why is
it needed?
The term axle ratio is, to be more exact, the ring gear
and pinion ratio. This means it is a comparison of the
number of teeth of the driving and driven gears. It was
found that the relative sizes of the driving and driven
SPIRAL BEVEL GEARS
Fig. 38—Typical Bevel Gears
gears affect the output speed and torque. As a simple
example, a ring gear with twice as many teeth as the
drive pinion, would turn at one half of pinion speed.
This also means that since the speed is cut in half, the
output torque is doubled. By applying basic laws of
gearing, each axle can be designed with the most
desirable axle ratio for specific applications.
The ratio numbers of an axle express the simplest
comparison of the number of ring gear teeth to each
drive pinion tooth. For example, the 4.11 to 1 ratio
means that for each pinion tooth there are 4.11 ring gear
teeth or, by the same token, the pinion turns 4.11
revolutions to each revolution of the ring gear.
When the actual component parts are seen, it is obvious
that there are more than 4.11 teeth on the ring gear and
1 tooth on the pinion. The 3.11:1 gear set has 37 teeth on
the ring gear and 9 on the drive pinion, or 37 -s- 9 =
4.11. These same divisions show that a gearset with 43
14 = 3.07, 41 h- 11 = 3.73, and 39
10 = 3.90.
Therefore, the axle ratio not only gives the gear speed
reduction and torque multiplication, but also states the
simple ratio of the number of ring gear teeth to each
drive pinion tooth.
The question of why this choice of ratios are available
has several answers. First, each engine has a definite
speed range in which it operates most efficiently, and
supplies maximum usable torque. To take advantage of
this built-in feature, a multiple speed transmission is
employed. This permits the operator to maintain proper
engine speed regardless of road speed. But, to make the
transmission as simple and practical as possible, high
gear is normally direct drive. This means that the engine
and drive shaft turn at the same relatively high rate of
speed with no torque multiplication. Since each vehicle’s
job application, engine, wheel size, and terrain condition
requires a specific speed and torque rate at the axle
shaft, the gear ration of the axle allows the tailoring of
the power train to the job.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR SU S P E N S IO N AND DRIVELINE
4-21
Differential Operation
A differential is an arrangement of gears that divides the
torque between the axle shafts and allows them to rotate
at different speeds. A basic differential consists of a set
of four gears. Two of these gears are called differential
side gears, and the other two are differential pinion
gears. Some differentials have more than two pinion
gears. Each side gear is splined to an axle shaft.
Consequently, each axle shaft must turn when its side
gear rotates.
The differential pinion gears are mounted on a
differential pinion shaft, and the gears are free to rotate
on this shaft. The pinion shaft is fitted into a bore in the
differential case and is at right angles to the axle shafts.
Power flow through the differential is as follows: The
drive pinion roates the ring gear. The ring gear, being
bolted to the differential case, rotates the case. The
differential pinion, as it rotates with the case, forces the
pinion gears against the side gears. When both wheels
have equal traction, the pinion gears do not rotate on the
pinion shaft because the input force on the pinion gear
is equally divided between the two side gears. See figure
40. Consequently, the pinion gears revolve with the
pinion shaft, but do not rotate around the shaft itself.
The side gears, being splined to the axle shafts and in
mesh with the pinion gears, rotate the axle shafts.
If a vehicle were always driven in a straight line, the ring
and pinion gears would be sufficient. The axle shaft
could then be solidly attached to the ring gear and both
driving wheels would turn at equal speeds.
However, if it became necessary to turn a corner, the
tires would scuff and slide because the outer wheel would
travel further than the inner wheel, as in figure 41. To
prevent tire scuffing and sliding, the differential becomes
effective and allows the axle shafts to rotate at different
speeds.
)
i/
Fig. 41—Need for Differential Action
As the inner wheel slows down, the side gear splined to
that axle shaft also slows down. At this point, the pinion
gears act as balancing levers by maintaining equal
speeds of rotation of the axle shafts. See figure 42. If the
vehicle speed remains constant and the inner wheel slows
to 90% of vehicle speed, the outer wheel speeds up to
110%. If the inner wheel slows to 75%, the outer wheel
would turn 125%. If one wheel stopped, the other wheel
would turn 200%.
BEARINGS
General Information
Roller bearings are precision products. Component parts
are carefully machined, heat treated and ground to
exacting tolerances and high surface finishes to provide a
maximum service life.
When properly installed, they demonstrate unusual
resistance to wear, heavy loads and difficult usage.
Despite their ruggedness, they are susceptible to
LIGHT DUTY TRUCK SERVICE MANUAL
4-22 REAR SUSPENSION AND DRIVELINE
mishandling in storage and installation. They are
adversely affected by dirt and they should be protected
from rust and corrosion.
Bearings are carefully assembled, washed, dried and
either lubricated or treated with a rust preventative at
the factory. They are then packaged for protection and
shipped to a distributor or to the ultimate user.
Bearings should not be removed from the original
packaging until they are ready for installation. When a
bearing is shipped from the factory it is ready for
installation. No cleaning or washing is recommended.
Field washing of new bearings, prior to installation,
seldom improves on the factory cleaning and could
impair the original cleanliness of the bearing.
Once a bearing has been removed from the original
packing, care must be exercised to prevent damage from
dirt and corrosion. Many bearing failures are the result
of improper handling, careless installation, misuse or
abuse rather than actual wear or fatigue in service.
The useful life expectancy of bearings can be greatly
extended if proper installation and maintenance
practices are observed.
Removal Procedures
Regardless of the means used to remove bearings or
races, it is absolutely essential that the driving force be
directed through the press fitted race. For example, if a
non-separable bearing is to be removed from a shaft, the
force must travel through the inner race and never
through the outer race, rollers or separator.
In most applications, it will be found that the roller
bearing has been assembled with a tight press fit holding
the rotating race, and with a relatively free fit holding
the stationary race. Removing the race with the free fit
can be done quite easily, but the race with the tight press
fit will require considerable force, which must be applied
in such a way that the bearings and component parts are
not damaged.
The Arbor Press. The arbor press is one means of
applying the force necessary to remove bearings or races
from shafts and housings. Its action is rapid, smooth and
positive, making it an especially useful tool where a
great deal of bearing removal work is done. In addition,
the arbor press can supply a greater force than is
available from most other bearing removal appliances,
making it possible to remove some bearings which might
not even be budged by bearing pullers or by hammering.
With the arbor press, the bearing is supported on the
press base plate with some simple accessories. These may
consist of flat bars placed beneath the inner race
adjacent to the shaft. A piece of flat stock with a
U-shaped cutout is preferable when this operation has to
be repeated often. A third type of accessory is the split
ring, a circular ring bored slightly larger than the shaft
diameter and sawed into two semi-circular segments.
The arbor press can only be used to remove races or
bearings from housings which are so designed that some
portion of the outer race can be exposed. In cases where
the entire face of the outer race is exposed, a section of
pipe or tubing, capped by a steel block, can be used. In
other cases, the shoulders against which the outer races
rest are slotted to allow a flat bar to contact the outer
race in two diagonally opposite places. The important
thing to remember in any of these operations is that the
force should only be directed through the press-fitted
race, and that the press base plate and accessories are
clean, and that all contacting surfaces are flat and true.
Bearing Pullers. Bearing pullers are a useful and
convenient means of removing bearings and races, where
no arbor press is available, or where the shaft is too
large or is obstructed and cannot go into a press.
The bearing puller must be applied so that the pressure
is directed through the press-fitted race, and that no
force is carried through the rollers or snap rings. The
puller can be used without accessories to draw off inner
races where no obstructions interfere and where long
reach is not necessary. In most cases, the split collar
puller plate is placed in back of the bearing to carry the
load directly to the inner race. In some applications, a
gear, pulley or cover plate can be used instead of the
split collar. When bearing pullers having adjustable legs
are used, it is im portant that the legs be of equal length
and symmetrically placed.
Cleaning of Used Bearings
Bearings which have been removed from service should
be cleaned before storing, even when the storage is to be
only of short duration. The bearing should be cleaned
thoroughly, removing all oil and hardened grease
accumulations, as well as any sludge which may be
deposited on the outer surfaces of the races. Remember
that cleaning of bearings is im portant and, whenever
possible, should be done before relubricating bearings.
Bearings can be cleaned easier and more thoroughly
when they have been removed from their housings and
shafts. When this is not possible, a light oil heated at
LIGHT DUTY TRUCK SERVICE MANUAL
REAR SUSPENSION AND DRIVELINE
4-23
Installation Procedures
Fig. 44—Typical Outer Race Removal
180&deg; to 200&deg;F should be flushed through the housing
while slowly rotating the bearing. Where the grease or
oil is badly oxidized and cannot be removed by this
method, a petroleum solvent such as kerosene or safetynaphtha may prove effective. In extreme cases, a mixture
of alcohol and kerosene or safety-naphtha will remove
the greater part of the sludge and scale. When petroleum
solvents, by themselves or with alcohol added, are used
in this manner, they should be followed by a flushing
with light oil before the lubricant is added to the
housing. This will wash away any of these solvents which
would otherwise dilute the lubricant.
Where it is possible to dismount the bearings, they
should be placed in a metal basket and suspended in a
container of some clean, cold petroleum product. There
they should soak, if possible, overnight. If no metal
basket is available, the bearings may be suspended in the
solution by a length of wire. Do not let the bearings rest
on the bottom of the container. If the lubricant is badly
oxidized, the bearings should be soaked in a light oil
heated at 180&deg; to 200&deg;F, and the basket or wire sloshed
through the oil slowly as often as possible. In cases of
extreme sludging, the bearings may be soaked in a
mixture of alcohol and kerosene or safety-naphtha.
In cleaning bearings, use plenty of clean rags for wiping
and handling. Do not use cotton waste as the short
threads may get into the bearings.
A brush may be useful in helping the oil or solvent to
remove dirt, scale or chips from bearings. Care should
be taken that none of the bristles become lodged
between the rollers and races, because a piece of bristle
can be as harmful as a steel chip.
Compressed air which is entirely free from condensed
moisture may be used to blow out bearings, but only
after all dirt and chips have been removed by sloshing or
brushing. Do not spin the bearings with compressed air
as dirt or chips present may cause indenting of the
raceways.
Before pressing a bearing back on the shaft, the bearing
seat should be thoroughly cleaned of all dirt, carbonized
lubricant or any other foreign matter present. Not only
may such things cause scoring of the shaft and the
bearing bore, but an improper bearing installation may
result. Dirt on the shaft may move ahead as the bearing
is pressed on the shaft, and pack between the inner race
and shaft shoulder. This in itself results in an improper
adjustment. If the dirt is later washed loose, the end
thrust on the bearing may cause a sideways movement of
the shaft which might cause misalignment of other
component parts.
After the bearing seat and the bearing bore have been
cleaned, they should be coated with lubricant. This not
only aids in pressing on the bearing but helps to prevent
the formation of rust at the press fit, and also assists any
later removal of the bearing.
The pressure required to drive bearings onto shafts or
into housings must be applied through the races. Where
bearings or bearing parts are assembled on shafts, apply
the pressure to the face of the inner race. Where
bearings or bearing parts are assembled in housings,
apply pressure to the face of the outer race. If the
pressure is directed through the wrong race or against
the rollers, cage or snap rings, brinelling, bending or
fracture may result.
The pressure, as well as going through the proper race,
should be directed straight and square. This means that
the pressure should be distributed as uniformly as
possible over the entire face of the race. Concentrating
the load on one side of the race will cause cocking and
may result in scoring the shaft or splitting the race. The
pressure should be directed straight down as a force
applied at an angle may result in damage to the shaft or
to the bearing separator or grease seal.
The Arbor Press. The arbor press provides one of the
best means of mounting bearings and races, for its
Fig. 45—Effect of Dirt on Bearing Seat
4 - 2 4 REAR SU S PEN SIO N AND DRIVELINE
E
_
1
r—
^
1
3) E 3)
PRESS R A M
_ _ STEEL
BLOCK
PIPE O R
&quot;‘&quot; 'T U B E
WRONG
RIGHT
nIE* _ _tl*n nDI .. In
&pound;
1
.............T
i
...
...... r
Fig. 46—Applying Pressure on the Correct Race
action is rapid and pressure can be applied continuously.
Special precaution should be taken when using the arbor
press to align the race squarely on the shaft, as the great
pressures which can be exerted by the press could easily
cause race cracking or severe scoring of the shaft, if the
race were started unevenly. Accessory equipment such as
drive plates, tubing or pipes which will carry the force
through the press fitted race, should be used whenever
necessary.
Drive Blocks. Drive blocks furnish one of the most
convenient means of driving a bearing onto a shaft or
into a housing. They are simple to construct and are
especially useful where the operation is repeated time
after time. Drive blocks can be used for either outer
race, inner race or complete bearing assembly. They
must be so constructed, however, that the pressure travels
only through the press-fitted race, and that the race is
brought up snug against the shoulder or other means of
retention provided for it.
Pipe or Tubing. Pipes or tubes can be used to assemble
Fig. 48—Bearing Installation Using Arbor Press
Fig. 49—Bearing Installation Using Drive Block
races or bearings in the same manner that they are used
to remove them. The same process can be used to drive
the outer race into the housing. Besides, pipe or tubing
can be used in conjunction with an arbor press as well as
with a hammer. The pressure should be distributed over
the end of the tube by means of a steel block or cap.
Points to Remember
Fig. 47—Apply Pressure Evenly
1. Make sure that shaft seat and housing bore are
clean, smooth and of the correct diameter.
2. Do not remove bearings from package until ready
for assembling.
3. Lubricate the surfaces of the bearings and machine
part which are to be press fitted.
4. Start bearings on shaft with rounded corner radius
of race going first.
5. Direct the driving pressure directly through race to
be press fitted, making sure that pressure is directed
straight and square.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
4 -2 5
6 . Never hammer directly on races or rollers, and
never use a wooden or soft metal mallet, as chips or
splinters may enter the bearing.
7. Use many smart quick taps rather than a few heavy
ones.
8 . Have straight square ends on driving accessories
and fixtures.
9. Drive races solidly up against shoulder of shaft and
housing.
10. Clean tools, clean hands and clean surroundings
are essential if damage to the bearing is to be
avoided.
Fig. 50—Bearing Installation Using Pipe or Tube
CO M PO N EN T PARTS REPLACEMENT
8 - 7 /8 Ring Gear Axle
AXLE ASSEMBLY
Construction of the axle assembly is such that service
operations may be performed with the housing installed
in the vehicle or with the housing installed in a holding
fixture. The following removal and installation procedure
is necessary only when the housing requires replacement.
CAU TIO N : See CAUTION on page 1 of this
section, regarding Axle Assembly fasteners.
Removal
1. Raise vehicle on hoist.
2. Support rear axle assembly with suitable lifting
device, so that tension is relieved in springs and
shock absorbers.
3. Remove trunnion bearing &quot;U &quot; bolts from the axle
companion flange, separate trunnion from flange,
position propeller shaft to one side and tie it to
frame side rail.
NOTE: Secure trunnion bearing caps to
trunnion, using masking tape or a large
rubber band, to prevent loss of bearings.
4. Disconnect shock absorbers at lower attachment
points and position out of the way.
5. Disconnect axle vent hose from vent connector and
position vent hose to one side.
6 . Disconnect hydraulic brake hose at connector on
axle housing. Remove brake drum, disconnect
parking brake cable at actuating levers and at
flange plate. Refer to Section 5 for cable removal
and brake details. Remove axle &quot;U &quot; bolt nuts, &quot;U &quot;
bolts, spacers and clamp plates.
7. Lower axle assembly and remove from vehicle.
Installation
1. Position axle assembly under vehicle and align with
springs.
2. Install spacer, clamp plate and &quot;U &quot; bolts to axle
assembly, loosely install retaining nuts to &quot;U &quot; bolts.
3. Position shock absorbers in lower attachment
brackets and loosely install nut to retain shock.
4. Connect axle vent hose to vent connector at carrier.
5. Connect hydraulic brake hose to connector on axle
housing, connect parking brake cable to actuating
levers. Install brake drum and wheel and tire
assembly—bleed brakes and adjust parking brake as
outlined in applicable portion of Section 5.
6 . Reassemble the propeller shaft to companion
flange, making sure that bearing caps are indexed
in flange seat. Torque bearing cap retaining nuts to
specifications.
7. Position vehicle so that weight is placed on
suspension components and torque affected parts to
specifications.
8 . Lower vehicle and remove from hoist.
AXLE SHAFT
Removal
1. Raise vehicle on hoist. Remove wheel and tire
assembly and brake drums.
2. Clean all dirt from area of carrier cover.
3. Drain lubricant from carrier by removing cover.
4. Remove the differential pinion shaft lock screw and
the differential pinion shaft as shown in figure 51.
5. Push flanged end of axle shaft toward center of
vehicle and remove &quot;C&quot; lock from button end of
shaft.
6 . Remove axle shaft from housing, being careful not
to damage oil seal.
LIGHT DUTY TRUCK SERVICE MANUAL
4 -2 6 REAR SU S PEN SIO N A ND DRIVELINE
Fig. 51—Differential Pinion Shaft Removal
Fig. 53—Wheel Bearing Removal
Oil Seal/Bearing—Replacement
1. Remove oil seal by using button end of axle shaft.
Insert button end behind the steel case of the oil
seal, then pry seal out of bore being careful not to
damage seal. If both seal and bearing are being
replaced proceed to step 2 .
2. Using J-23689, insert into bore so that tool grasps
behind the bearing. See figure 53. Slide washer
against outside of seal (or bearing) and turn nut
finger tight against washer. Attach Slide Hammer
J-2619 and remove bearing and seal.
3. Back off nut and remove bearing and seal from
tool.
4. Lubricate cavity between seal lips with wheel
bearing lubricant and also lubricate new bearing
with wheel bearing lubricant.
5. To reinstall bearing, use J-23690 Installer. Install
bearing until tool bottoms against tube as
illustrated in figure 54.
BEARING]
J-8 0 9 2
Fig. 54—Wheel Bearing Installation
6 . To install oil seal, place seal on J-21128 and drive
into bore until tool bottoms against end of tube. See
figure 55. This tool installs the seal flush with the
end of the tube.
Brake Backing Plate—Replacement
Fig. 52—Oil Seal and Wheel Bearing
1. Remove brake line at wheel cylinder inlet and
disassemble brake components from flange plate.
Refer to Section 5 for brake disassembly procedure.
2. Remove bolts retaining flange plate to axle, and
remove flange plate.
3. Install new flange plate to axle housing and torque
nuts to specifications.
4. Install brake components on flange and connect
hydraulic line to wheel cylinder inlet. See Section 5
for brake assembly, bleeding and adjustment
procedures.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
Fig. 55—Seal Installation
Axle Shaft—Installation
1. Slide axle shaft into place.
Exercise care that splines on end of
shaft do not damage oil seal and that they
engage with splines of differentialside gear.
Install axle shaft &quot;C&quot; lock on button end of
CAUTION:
2.
axle
shaft and push shaft outward so that shaft lock
seats in counterbore of differential side gear.
3. Position differential pinion shaft through case and
pinions, aligning hole in shaft with lock screw hole.
Install lock screw and torque to specifications.
4. Using a new gasket, install carrier cover and torque
bolts to specifications.
CAUTION: Make sure both gasket surfaces on
carrier and cover are clean before installing
new gasket. Torque carrier cover bolts in a
crosswise pattern to ensure uniform draw on
cover gasket.
5. Fill axle with lubricant as specified in Section 0 of
this manual to a level even with the bottom of filler
hole.
6 . Install brake drum and wheel and tire assembly.
7. Lower vehicle and remove from hoist.
4 -2 7
Fig. 56—Pressing Out Wheel Stud
6 . Remove lug nut.
7. Reinstall brake drum and wheel and tire.
8 . Lower vehicle and remove from hoist.
PINION FLANGE, DUST DEFLECTOR
AND/OR OIL SEAL
Removal
1. Raise vehicle on hoist.
2. Disconnect propeller shaft from axle.
3. Position propeller shaft to one side and tie it to
frame side rail.
4. Measure the torque required to rotate the pinion, as
shown in figure 57. Record the torque for later
reference.
5. Scribe a line down pinion stem, pinion nut, and
flange to aid on reinstallation. Make sure lines show
the relationship of components accurately. Count
Wheel Bolt—Replacement
1. Raise vehicle on hoist allowing axle to hang freely.
2. Remove wheel and tire and brake drum.
3. Using Tool J-5504 or J-6627 press out stud as shown
in figure 56.
4. Place new stud in axle flange hole. Slightly start
stud serrations in hole by firmly pressing back of
stud with your hand.
5. Install a lug nut with flat side first (tapered face
outboard). Tighten on lug nut drawing stud into
flange until stud head is bottomed on back side of
flange.
Fig. 57—Measuring Pinion Rotating Torque
LIGHT DUTY TRUCK SERVICE MANUAL
4 -2 8 REAR SUSPENSION AND DRIVELINE
the number of exposed threads on pinion stem, and
record for later reference. See figure 58.
6 . Install Tool J-8614-11 on pinion flange and remove
pinion flange self-locking washer faced nut as
shown in figure 59. (Position J-8614-11 on flange so
that the four notches are toward flange.) Save
scribed nut for reinstallation.
7. Thread pilot end of Tool J-8614-3 into small O.D.
end of J-8614-2. Then with J-8614-11 installed as in
Step 6 , insert J-8614-2 into J-8614-11 and turn it 45
degrees to locked position. Remove flange by
turning J-8614-3 while holding J-8614-11 as shown
in figure 60.
8 . Pry old seal out of bore, using a screw driver or a
hammer and chisel.
Fig. 60—Drive Pinion Flange Removal
Inspection
1. Inspect pinion flange for smooth oil seal surface,
worn drive splines, damaged ears, and for
smoothness of bearing contact surface. Replace if
necessary.
2. If deflector requires replacement, remove by
tapping from flange, clean up stake points; install
new deflector, and stake deflector at three new
equally spaced positions.
NOTE: Staking operation must be performed
in such a manner that the seal operating
surface is not damaged.
Installation
1. Lubricate cavity between the seal lips of the pinion
flange oil seal with a lithium-base extreme pressure
lubricant.
2. Position seal in bore and place gauge plate J-228041 over seal and against seal flange. The gauge plate
assures proper seating of seal in carrier bore.
3. Use J-21057, as shown in figure 61, to press seal
into carrier bore until gauge plate is flush with the
carrier shoulder and seal flange. Turn gauge plate
180&deg; from installed position; seal must be square in
carrier bore to seal properly against pinion flange.
4. Lubricate the cavity between end of pinion splines and
pinion flange with a non-hardening sealer (such as
Fig. 59—Removing Nut from Drive Pinion
Fig. 61—Pinion Oil Seal Installation
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A ND DRIVELINE
Permatex Type A or equivalent) prior to installing
washer and nut on pinion.
5. Using J-8614-11 as shown in figure 62, install flange
onto pinion. Install washer and nut, and tighten nut
to original position. Refer to scribe marks and
number of exposed threads, recorded earlier.
NOTE: Do not attempt to hammer the flange
onto pinion shaft. To do so may damage the
ring gear and pinion.
6 . Measure rotating torque of pinion and compare
with torque recorded before removal. Tighten
pinion nut in additional small increments until the
torque necessary to rotate the pinion exceeds the
original figure by 1 to 5 inch pounds. Do not exceed
the original torque by more than 5 inch pounds.
7. Reattach propeller shaft and torque to specifica&shy;
tions. Reinstall brake drums and wheels.
CAUTION: See CAUTION on page 1 of this
section regarding the fasteners referred to in
step 7.
8 . Lower vehicle and remove from hoist.
1 0 -1 /2 and 1 2 - 1 /4 RING GEAR
AXLES
AXLE ASSEMBLY
Service operations on these axle assemblies may be
performed with the housing installed in the vehicle or
with the housing installed in a holding fixture. There
may be occasions, however, when it will be necessary to
remove the complete housing assembly. The following
axle assembly removal and installation procedure,
therefore, is necessary only when housing replacement is
required.
CAUTION: All axle attachments are important
attaching parts. See CA UTION on page I of
this section.
Removal
1. Raise vehicle, place stand jacks under frame side
rails, and remove rear wheels.
2. Remove two trunnion bearing &quot;U&quot; bolts from the
3.
4.
5.
6.
4 -2 9
rear yoke, split rear universal joint, position
propeller shaft to one side, and tie it to the frame
side rail.
NOTE: The bearings can be left on the
trunnion and held in place with tape.
Remove hub and drum assembly and disconnect
parking brake cable at lever and at flange plate. See
Section 5 for cable removal.
Disconnect hydraulic brake hose at connector on
rear axle housing. Refer to Section 5.
Disconnect shock absorbers at axle brackets.
Support axle assembly with hydraulic jack, remove
spring &quot;U &quot; bolts, and lower axle assembly to the
floor.
Installation
1. Place axle assembly under vehicle, raise into
position, install spring &quot;U &quot; bolts, anchor plates and
nuts, and tighten securely.
2. Connect and secure shock absorbers to axle
brackets.
3. Connect brake hose at connector on rear axle
housing.
4. Install hub and drum assembly. Connect parking
brake cable at lever and flange plate. Bleed brake
hydraulic system and adjust parking brake.
5. Reassemble the rear universal joint, making sure
that &quot;U &quot; bolts are drawn up tight and locked
properly. Caution should be taken not to over&shy;
tighten &quot;U &quot; bolt nuts and cause bearing cups to
become distorted.
6 . Install rear wheels, remove stand jacks, and lower
vehicle.
7. Test operation of brakes and rear axle.
AXLE VENT—12-1/4&quot; RING GEAR AXLE
Replacement
Service replacement axle housing assemblies are not
equipped with an axle vent; therefore, always make sure
that a new vent assembly is installed when replacing the
housing. If axle vent requires replacement, pry old vent
from housing being sure that entire vent is removed.
Prick punch around carrier hole to insure fit of
replacement vent. Tap new vent into housing using a
soft-faced hammer. Vent should be positioned in housing
so that flat surface is toward centerline of differential
carrier. See figure 63.
AXLE S H A F T -10-1/2&quot; AXLES
Replacement
Fig. 62—Installing Pinion Flange
1. Remove bolts and lock washers that attach the axle
shaft flange to the wheel hub. See figure 64.
2. Rap on flange with a soft-faced hammer to loosen
shaft. Grip the rib on end of flange with a pair of
LIGHT DUTY TRUCK SERVICE MANUAL
4 - 3 0 REAR SU SPEN SION A ND DRIVELINE
Fig. 65—Removing Axle Shaft—11,000 # Axle
Fig. 63—Typical Axle Vent Installation
locking pliers and twist to start shaft removal.
Remove shaft from axle tube.
3. Thoroughly clean both the axle shaft flange and the
end of the wheel hub.
NOTE: Any lubricant on these surfaces tends
to loosen axle hsaft flange bolts.
4. Place a new gasket over the axle shaft and position
the axle shaft in the housing so that the shaft
splines enter the differential side gear. Position
gasket so that holes are in alignment and install
flange-to-hub attaching bolts. Torque bolts to
specifications.
AXLE SHAFT—12-1/4&quot; AXLES
Replacement
1. Remove hub cap, and install Tool J-8117 in tapped
hole on shaft flange.
2. Install slide hammer (Tool J-2619) and remove axle
shaft, as shown in figure 65.
3. Thoroughly remove old gasket material from hub
and hub cap. Clean shaft flange and mating
surfaces in the wheel hub.
4. Install axle shaft so that the flange splines index
into hub splines. Tap shaft into position, using
J-8117 and J-2619.
5. Install new gasket, position flange to hub and install
attaching bolts. Torque bolts to specifications.
HUB AND DRUM ASSEMBLY—FIGS. 66, 67
Removal
1. Remove axle shaft as outlined earlier.
2. Disengage tang of retainer from slot or flat of
locknut, then remove locknut from housing tube,
using appropriate tool, as shown in figure 68 .
a. J-2222—10-1/2&quot; axles.
b. J-0870—12-1/4&quot; axles.
3. Disengage tang of retainer from slot or flat of
adjusting nut and remove retainer from housing
tube.
4. Use appropriate tool as specified in Step 2 to
remove adjusting nut from housing tube.
NOTE: Remove thrust washer from housing
tube.
5. Pull hub and drum assembly straight off axle
housing, using care on the 11,000 lb. axles to avoid
dropping outer bearing inner race and roller
assembly.
6 . Remove oil seal, and discard.
Bearing/Cup—Removal
For 1 0 -1 /4 &quot; Axles
Fig. 64—Removing Flange-to-Hub Bolts
1. Use a hammer and long drift to knock the inner
bearing, cup and oil seal from the hub assembly.
2. Remove outer bearing snap ring with a pair of
pliers.
3. With J-24426 on Handle J-8092, as shown in figure
69, drive outer bearing and cup from the hub
assembly.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
4-31
12 1 1 1 0 9
1.
A x le S h aft
2.
S h a ft-to -H u b B o lt
8.
3.
Locknut
9.
4.
L o c k n u t Re tain e r
5.
6.
7.
S n a p R in g
H u b In n e r B e arin g
10.
O il Seal
A d ju s tin g N u t
11.
W heel B o lt
T h ru s t W asher
12.
H u b A ss e m b ly
H u b O u t e r B e arin g
13.
D ru m A ss e m b ly
1. A x 1e S h a ft
2 . A x le S h a ft-to - W h e e l
Hub R e ta in in g B o lt
3 . A d ju s tin g N u t L o c k n u t
4 . Hub O u te r B earing
Assem bly
5. Hub O u te r Bearing
R e ta in e r
6. W heel B o lt
7. Drum
8. O il D e fle c to r
9 . O il D e fle c to r
10. O il Seal
11. Hub Inner Bearing
A ssem bly
12. D r u m -to -H u b R e ta in in g S crew
13. Thrust W asher
14. Bearing A d ju s tin g N u t
15. A d ju s tin g N u t Lock
16. G a s k e t
Fig. 67—Hub and Drum Assembly—12-1/4&quot; Axles—
11 ,000 #
Fig. 66—Hub and Drum Assembly—10-1/2&quot; Axles
For 12-1/4&quot; Axles
1. Cut a suitable length of 1/2 inch steel bar stock for
press-out tool as shown in figure 70.
2. Place bar stock tool behind inner bearing cup,
index tool in provided notches, and press out cup
with an arbor press.
3. Use J-22380, as shown in figure 71, to remove outer
bearing retainer ring.
4. Remove the outer bearing by driving on the axle
shaft spacer, using the splined flange cut from an
old axle shaft, as shown in figure 72.
Inspection and Cleaning o f Bearings
1. Inspect bearing rollers for excessive wear, chipped
edges, and other damage. Slowly move rollers
around cone to detect any flat or rough spots on
rollers or cone.
2. Examine bearing cups in hub for pits, cracks, and
other damage.
3. Examine axle shaft flange studs, wheel studs, hub
splines, hub bore, and tapped holes for evidence of
damage. Clean up threads or replace parts where
required.
4. Examine oil seal sleeve for evidence of wear or
Fig. 68—Removing Lock Nut—Typical
roughness, check axle housing oil deflector and
brake drum oil deflector for evidence of damage.
Replace parts where required.
5. Examine brake drum for excessive scoring and
other damage. To replace brake drum refer to
&quot;Brake Drum Replacement.&quot;
6.
Immerse bearing cone and roller assemblies in
LIGHT DUTY TRUCK SERVICE MANUAL
4 -3 2 REAR SU S PEN SIO N AND DRIVELINE
Haw*
*—
Fig. 69—Removing Outer Bearing and Cup
cleaning solvent. Clean with stiff brush to remove
old lubricant. Blow bearings dry with compressed
air, directing air stream across bearing. Do not spin
bearings while blowing them dry.
7. Thoroughly remove all lubricant from axle housing
tube and from inside the hub, wipe dry. Make sure
all particles of gasket are removed from outer end
of hub, axle shaft, and hub cap.
8 . Scrape old sealing compound out of oil seal bore in
the hub.
4. Withdraw cup installer, then install retainer ring,
using J-22380 as shown in figure 71. Press the cup
into contact with the retainer ring as shown in
figure 72.
NOTE: The bearing cup-to-retainer ring
seating procedure is essential to assure that
an accurate wheel bearing adjustment will be
Bearing/Cup—Installation
For 10-1/4&quot; Axles—
1. Place outer bearing into hub.
2. Install cup of outer bearing into hub by using
Handle J-8092 and J-8608, installed upside-down.
Be sure J-8608 is upside down on driver handle, so
that chamfer does not contact bearing cup.
3. Drive cup beyond the snap ring groove.
4. Using a pair of pliers, install snap ring into its
groove.
5. Drive cup back against snap ring by using J-24426,
as shown in figure 69.
6 . To install inner bearing cup, use J-24427 on Handle
J-8092. Drive cup into place until it seats against
shoulder of hub bore.
7. Install new oil seal with J-24428.
For 12-1/4&quot; Axles—
1. To install outer bearing, place axle shaft spacer in
hub, followed by the outer bearing. The larger O.D.
of the bearing goes toward the outer end of the
hub.
2. Position outer bearing cup in hub with the thin
edge of the cup toward the outer end of the hub.
3. Press the cup into the hub, using J-8114 and Handle
J-8092.
Fig. 71—Removing Hub Outer Bearing Retainer Ring
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A N D DRIVELINE
4 -3 3
Fig. 74—Installing Hub Oil Seal
Fig. 72—Removing Hub Outer Bearing
obtained, and that the adjustment will not
loosen during vehicle operation.
5. To install inner bearing, use J-8093 with Handle
J-8092 to drive cup into hub bore, as shown in
figure 73.
6 . Install new oil seal, using J-22354 as shown in figure
74.
Drum—Non-Demountable-Type—Fig. 66
Replacement
Construction of the nondemountable-type hub and drum
assembly is such that replacement cannot be accom&shy;
plished with the hub assembly installed on the vehicle.
1. Separate the drum and hub by removing the drumto-hub retaining bolts, hub stud nuts, or by pressing
out the wheel studs, as applicable.
2. Position brake drum to hub assembly, making
certain that all drain holes are in alignment.
3. Apply a light, even coating of sealing compound to
the hub oil deflector contact surface, and position
deflector to drum.
4. Install drum-to-hub retaining bolts, hub stud nuts,
or press wheel studs into drum, as applicable.
Drum—Demountable-Type—Fig. 67
Replacement
The demountable-type drum may be separated from the
hub and removed from the vehicle without disturbing
the axle shaft and hub. The drum is held to the hub by
countersuck, slotted screws, which are easily removed
with a screw driver.
Wheel Bolt
Replacement
Fig. 73—Installing Hub Inner Bearing Cup
Wheel bolts are serrated and may also be swaged in
place; however, replacement procedure remains the same
for both types of installation.
Press bolts out of hub flange and press new bolts into
place, making sure they are a tight fit. If all bolts are
removed, be sure that hub oil deflector is in position
under bolt heads. See figure 75.
LIGHT DUTY TRUCK SERVICE MANUAL
4 - 3 4 REAR SU S PEN SIO N AND DRIVELINE
REMOVAL
INSTALLATION
rig. 75—Wheel Bolt Replacement
3. Use appropriate tool as listed for the specified axle:
a. J-2222 for 10-1/2&quot; axles.
b. J-0870 for 12-1/4&quot; lb. axles.
4. Tighten inner adjusting nut to specified torque at
the same time rotating hub to make sure all bearing
surfaces are in contact. Then back off inner nut to
specified amount of turn-back.
See figure 76, and refer to Specifications Section for
torque values.
5. Install tanged retainer against the inner adjusting
nut. Align inner adjusting nut so short tang of
retainer will engage nearest slot on inner adjusting
nut.
6 . Install outer locknut and tighten to correct specified
torque. Then bend long tang of retainer into slot of
outer nut. This method of adjustment will result in
the proper bearing adjustment.
Installation of Hub and. Drum Assembly
1. Using a high melting point EP bearing lubricant,
liberally pack bearings and apply a light coat on
I.D. of hub bearing contact surface and O.D. of
axle housing tube.
2. Make sure inner bearing, oil seal, axle housing oil
deflector, and inner bearing race and oil seal are
properly positioned.
3. Install hub and drum assembly on axle housing,
exercising care so as not to damage oil seal or
dislocate other internal components.
4. On the 12-1/4&quot; axles, place outer bearing cone and
roller assembly on axle housing and press firmly
into hub with hand.
5. On 10-1/2&quot; axles, install thrust washer so that tang
on I.D. of washer is in keyway on axle housing.
6 . Install adjusting nut and complete the installation
as directed under &quot;Bearing Adjustment.&quot;
DRIVE PINION OIL SEAL
Replacement
1.
2.
3.
4.
5.
NOTE: The pinion oil seal may be replaced
with the carrier assembly installed in the
vehicle.
Disconnect propeller shaft.
Scribe a line down the pinion stem, pinion nut and
companion flange.
Use J-8614 to remove the pinion nut and the com&shy;
panion flange.
For 12-1/4&quot; axles, remove the bolts retaining the oil
seal retainer to the carrier, and remove the retainer. See
figure 77.
Pry the oil seal from the bore, using care not to damage
the machined surfaces. Thoroughly clean all foreign
material from contact area.
BEARING ADJUSTMENT
Before checking bearing adjustment, make sure brakes
are fully released and do not drag.
Check bearing play by grasping tire at top and pulling
back and forth, or by using a pry bar under tire. If
bearings are properly adjusted, movement of brake
drum in relation to brake flange plate will be barely
noticeable and wheel will turn freely. If movement is
excessive, adjust bearing as follows:
1. Remove axle shaft and raise vehicle until wheel is
free to rotate.
2. Disengage tang of retainer from locknut and
remove both locknut and retainer from axle
housing tube.
Fig. 76—Tightening Adjusting Nut—Typical
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S P E N S IO N A N D DRIVELINE
4 -3 5
6 . Lubricate the cavity between the seal lips with a high
melting point bearing lubricant.
7. Install a new pinion oil seal into the bore, using
J-24434 for Chevrolet 10-1/2” axles, J-24384 for Dana
10-1/2&quot; axles, and J-22281 for 12-1/4&quot; axles. Be sure
seal bottoms against shoulder in bore.
8 . For 12-1/4&quot; axles, install the bearing retainer to the
carrier.
9. Reinstall the companion flange, pinion nut and pro&shy;
peller shaft.
CAUTION: See CAUTION on page 1 o f this
section, regarding the above fasteners.
Fig. 77—Pinion Oil Seal—12-1/4” A xle
DIFFERENTAIL D IA G N O S IS
STANDARD DIFFERENTIAL
Noise
The most essential part of rear axle service, as with any
mechanical repair, is proper diagnosis of the problem, and, in
axle work one of the most difficult areas to diagnosis is noise.
Locating a broken axle shaft, or broken differential gear,
presents little or no problem, but, locating and isolating axle
noise can be an entirely different matter.
Fig. 78—Noise Level
Degree of Noise
Any gear driven unit, and especially an automotive drive
axle where engine torque multiplication occurs at a 90&deg;
turn in the drive line, produces a certain amount of
noise. Therefore, an interpretation must be made for
each vehicle to determine whether the noise is normal or
if a problem actually exists. A normal amount of noise
must be expected and cannot be eliminated by
conventional repairs or adjustment. See figure 78.
Acceptable noise can be defined as a slight noise heard
only at a certain speed or under unusual or remote
conditions. For example, this noise tends to reach a
&quot;peak&quot; at speeds from 40 to 60 miles per hour
depending on road and load conditions, or on gear ratio
and tire size. This slight noise is in no way indicative of
trouble in the axle assembly.
Drive line noises may baffle even the best diagnostician.
Vehicle noises coming from tires, transmission, propeller
shaft, universal joints, and front or rear wheel bearings,
are often mistaken for axle noise. Such practices as:
raising tire pressure to eliminate tire noise (although this
will not silence tread noise of mud and snow tires),
listening for the noise at varying speeds and road
surfaces, on drive, float, and coast conditions will aid in
locating the source of alleged axle noises. Thus, every
effort should be made to isolate the noise to a specific
drive line component instead of making a random guess
that could be a costly waste of time.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR SU S PEN SIO N AND DRIVELINE
Elimination of External Noises
When a rear axle is suspected of being noisy, it is
advisable to make a thorough test to determine whether
the noise originates in the tires, road surface, front wheel
bearings, engine, transmission, or rear axle assembly.
Noise which originates in other places cannot be
corrected by adjustment or replacement of parts in the
rear axle assembly.
Road Noise—Some road surfaces, such as brick or roughsurfaced concrete, cause noise which may be mistaken
for tire or rear axle noise. Driving on a different type of
road, such as smooth asphalt or dirt, will quickly show
whether the road surface is the cause of noise. Road
noise usually is the same on drive or coast.
Tire Noise—Tire noise may easily be mistaken for rear
axle noise, even though the noisy tires may be located on
the front wheels. Tires worn unevenly, or having surfaces
on non-skid divisions worn in saw-tooth fashion, are
usually noisy and may produce vibrations which seem to
originate elsewhere in the vehicle. This is particularly
true with low tire pressure.
Test for Tire Noise—Tire noise changes with different
road surfaces, but rear axle noise does not. Temporarily
inflating all tires to approximately 50 pounds pressure,
for test purposes only will materially alter noise caused
by tires but will not affect noise caused by the rear axle.
Rear axle noise usually ceases when coasting at speeds
under 30 miles per hour; however, tire noise continues
but with lower tone as vehicle speed is reduced. Rear
axle noise usually changes when comparing &quot;pull&quot; and
j &quot;coast&quot; but tire noise remains about the same.
Engine and Transmission Noises—Sometimes a noise
which seems to originate in the rear axle is actually
: caused by the engine or transmission. To determine
I which unit is actually causing the noise, observe
approximate car speeds and conditions under which the
noise is most pronounced; then stop vehicle in a quiet
place to avoid interfering noises. With transmission in
neutral, run engine slowly up and down through engine
speeds corresponding to vehicle speed at which the noise
was most pronounced. If a similar noise is produced with
vehicle standing, it is caused by the engine or
transmission and not the rear axle.
Front Wheel Bearing Noise—Loose
or rough front wheel
bearings will cause noise which may be confused with
rear axle noises; however, front wheel bearing noise does
not change when comparing &quot;pull&quot; and &quot;coast&quot;. Light
application of brake, while holding vehicle speed steady,
will often cause wheel bearing noise to diminish, as this
takes some weight off the bearing. Front wheel bearings
may be easily checked for noise by jacking up the wheels
and spinning them, and also be shaking wheels to
determine if bearings are excessively loose.
Body Boom Noise or Vibration
Objectional &quot;body boom&quot; noise or vibration at 55-65
mph can be caused by an unbalanced propeller shaft.
Excessive looseness at the spline can contribute to this
unbalance.
Other items that may also contribute to the noise
problem are as follows:
1. Undercoating or mud on the shaft, causing
unbalance.
2. Shaft or companion flange balance weights missing.
3. Shaft damage, such as bending, dents, or nicks.
4. Tire-type roughness. Switch tires from a known
good car to determine tire fault.
If, after making a comprehensive check of the vehicle,
all indications point to the rear axle, further diagnostic
steps are necessary to determine the axle components at
fault. True axle noises generally fall into two categories:
gear noise and bearing noise.
Rear Axle Noises
If a careful test of vehicle shows that noise is not caused
by external items it is then reasonable to assume that
noise is caused by rear axle assembly. The rear axle
should be tested on a smooth level road to avoid road
noise. It is not advisable to test rear axle for noise by
running with rear wheels jacked up.
Noises in rear axle assembly may be caused by a faulty
propeller shaft, faulty rear wheel bearings, faulty
differential or pinion shaft bearings, misalignment
between two U-joints, or worn differential side gears and
pinions; noises may also be caused by mismatched,
improperly adjusted, or scored ring and pinion gear set.
Rear Wheel Bearing Noise—A rough rear wheel bearing
produces a vibration or growl which continues with
vehicle coasting and transmission in neutral. A brinelled
rear wheel bearing causes a knock or click approximately
every two revolutions of rear wheel, since the bearing
rollers do not travel at the same speed as the rear axle
and wheel. With rear wheels jacked up, spin rear wheels
by hand while listening at hubs for evidence of rough or
brinelled wheel bearing.
Differential Side Gear and Pinion Noise—Differential
side gears and pinions seldom cause noise since their
movement is relatively slight on straight ahead driving.
Noise produced by these gears will be most pronounced
on turns.
Pinion Bearing failures can be distinguished because
they rotate at higher speeds than differentia] side
bearings and axle shaft bearings. Rough or brinelled
pinion bearings produce a continuous low pitched
whirring or scraping noise starting at relatively low
speed.
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S PEN SIO N A ND DRIVELINE
4 -3 7
Side Bearings produce a constant rough noise of a lower
pitch than pinion bearings. Side bearing noise may also
fluctuate in the above wheel bearing test.
NOTE: Bearing Diagnosis Charts appear
later in this section.
Gear Noise
There are two basic types of gear noise. The first type is
produced by broken, bent, or forcibly damaged gear
teeth and is usually quite audible over the entire speed
range and presents no particular problem in diagnosis.
For example, hypoid gear tooth scoring as seen in figure
79 generally results from the following: insufficient
lubricant improper breakin, improper lubricant, insuffi&shy;
cient- gear backlash, improper ring and pinion gear
alignment, or loss of drive pinion nut torque. The
scoring will progressively lead to complete erosion of the
gear tooth, or gear tooth pitting and eventual fracture if
the initial scoring condition is not corrected. Another
cause of hypoid tooth fracture is extended overloading
of the gear set which will produce fatigue fracture, or
shock loading which will result in sudden failure.
Differential pinion and side gears rarely give trouble.
Common causes of differential failure are shock loading,
extended overloading, and seizure of the differential
pinions to the cross shaft resulting from excessive wheel
spin and consequent lubrication breakdown.
The second type of gear noise pertains to the mesh
pattern of the gear teeth. This form of abnormal gear
noise can be recognized as it produces a cycling pitch
(whine) and will be very pronounced in the speed range
at which it occurs, appearing under either &quot;drive&quot;,
&quot;float&quot; or &quot;coast&quot; conditions. &quot;Drive&quot; is acceleration or
heavy pull. &quot;Coast&quot; is with a closed throttle and vehicle
in gear and &quot;float&quot; is using just enough throttle to keep
the car from driving the engine—the vehicle slows down
gradually but engine still pulls slightly. Gear noise tends
to peak in a narrow speed range or ranges, and will tend
to remain constant in pitch. Bearing noise will vary in
pitch with vehicle speeds. See figure 80.
LIGHT DUTY TRUCK SERVICE MANUAL
4 -3 8 REAR SU SPEN SION AND DRIVELINE
A GENERAL DIAGNOSTIC PROCEDURE FOR
ISOLATING REAR AXLE NOISE PROBLEMS
Cause
Problem
1. Noise is the same in drive or coast
1. a) Road noise
b) Tire noise
c) Front wheel bearing noise
2 . Noise changes on a different type of road
2. a) Road noise
b) Tire noise
3. Noise tone lowers as car speed is lowered
3. Tire noise
4. Similar noise is produced with car standing
and driving
4. a) Engine noise
b) Transmission noise
5. Vibration
5. a)
b)
c)
d)
e)
6 . A knock or click approximately every two
6 . A brinelled rear wheel bearing
7. Noise most pronounced on turns
7. Differential side gear and pinion
8 . A continuous low pitch whirring or scraping
8 . Pinion bearing
9. Drive noise, coast noise or float noise
9. Ring and pinion gear
Rough rear wheel bearing
Unbalanced or damaged propeller shaft
Tire unbalance
Worn universal joint in propeller shaft
Mis-indexed propeller shaft at companion
flange
f) Companion flange runout too great
revolutions of rear wheel
noise starting at relatively low speed
10 . Clunk on acceleration or deceleration
10. Worn differential cross shaft in case
11 . Grunt on stops
11. No grease in propeller shaft slip yoke
12 . Groan in Forward or Reverse
12. Wrong lube in differential
13. Chatter on turns
13. a) Wrong lube in differential
b) Clutch plates worn
14. Clunk or knock on rough road operation
14. Excessive end play of axle shafts to differential
cross shaft
Fig. 80—Diagnosis of Noise Problems
LIGHT DUTY TRUCK SERVICE MANUAL
REAR S U S P E N S IO N A N D DRIVELINE
4 -3 9
DIFFERENTIAL A N D REAR AXLE BEARING DIAGNOSIS
CO NSIDER THE FO LLO W IN G FAC TO R S W HEN D IA G N O S IN G B E A R IN G C O N D IT IO N :
ABRASIVE
R OL LER
1.
G E N E R A L C O N D IT IO N OF A L L PARTS D U R IN G D ISASSEM BLY A N D IN SPECTION
2.
C L A S S IF Y THE F A IL U R E W ITH THE A ID OF THE IL L U S T R A T IO N S
3.
D E T E R M IN E THE CAUSE.
4.
M A K E A L L REPAIRS FO LLO W IN G RECO M M END ED PROCEDURES
WEAR
GALLING
BE NT C A G E
P A T T E R N ON RACES A N D R O LLE R S CAU SED BY
FINE ABRA S IV ES.
M E T A L SMEARS ON R O LLE R ENDS DUE TO O V E R H E A T
L U B R IC A N T F A IL U R E OR O V E R L O A D (W AGON'S)
CAGE D A M A G E DUE TO IM PROPER H A N D L IN G
OR TOOL USAGE
C L E A N A L L PARTS A N D HOUSINGS. CHECK SEALS
A N D BEA R IN G S A N D REPLACE IF L E A K IN G . ROUGH
OR N O ISY.
REPLACE BE A R IN G
CHECK SEALS A N D CHECK
FOR PROPER L U B R IC A T IO N .
REPLACE B EAR IN G
ABRASIVE
STEP W E A R
BENT
ETCHING
B E A R IN G SU RFACES APPEAR G R A Y OR G R A Y IS H
BLA C K IN CO LO R W ITH R E L A T E D ETCHIN G A W AY
OF M A T E R IA L U S U A L L Y AT R O LLE R SPACING.
P A T T E R N ON R O LLE R E N D S C A U S E D BY
FIN E A B R A S IV E S .
C L E A N A L L PARTS A N D HOUSIN GS. CHECK SEALS
A N D B E A R IN G S A N D REPLACE IF L E A K IN G , ROUGH
OR NOISY
INDENTATIONS
REPLACE BE A R IN G .
REPLACE B E A R IN G S CHECK SEALS A N D CHECK
FOR PROPER LU B R IC A T IO N .
CAGE
SURFACE DEPRESSIONS ON RACE A N D R O LLER S
CA U S ED BY H A R D P A R T IC LES OF FO R EIG N M A T E R IA L .
C L E A N A L L PARTS A N D HOUSINGS CHECK SEALS
A N D R EPLACE B E A R IN G S IF ROUGH OR NOISY.
CAGE
CAGE D A M A G E DUE TO iM PHUPER H A N D L IN G
OR TO O L USAGE
WEAR
W EAR A R O U N D OU TSIDE D IA M E T E R OF CAGE A N D
R O LLE R POCKETS CAUSED BY A B R A S IV E M A T E R IA L
A N D IN E F F IC IE N T L U B R IC A T IO N .
C LE A N R E L A T E D PARTS A N D HOUSINGS.
CHECK SEALS A N D REPLACE BEAR IN G S.
M ISALIG NM ENT
OUTER RACE M IS A L IG N M E N T DUE TO FO R EIG N
OBJECT.
C LE A N R E L A T E D PARTS A N D R EPLACE B E A R IN G .
M A K E SURE RACES AR E PR O PER LY SEATED.
Fig. 81 —Differential and Axle Bearing Diagnosis Chart A
LIGHT DUTY TRUCK SERVICE MANUAL
4 - 4 0 REAR SU SPEN SION AND DRIVELINE
DIFFERENTIAL A N D REAR AXLE BEARING D IA GNOSIS
(C O N T ’D)
CR ACK ED INNER
RACE
FATIGUE SPALLING
RACE CRACKED DUE TO IMPROPER FIT,
COCKING, OR POOR BEARING SEATS.
FLA K IN G OF SURFACE M ETAL RESULTING FROM
FATIGUE.
REPLACE BEARING A ND CORRECT BEARING
SEATS.
REPLACE BEARING
B R IN ELL ING
SURFACE INDENTATIO NS IN RACEWAY CAUSED BY
ROLLERS EITHER UNDER IMPACT LOADING OR
V IB R A TIO N W HILE THE BEARING IS NOT RO TATING .
CLEAN A L L R ELATED PARTS.
REPLACE BEARING IF ROUGH OR NOISY.
FRETTAGE
STAIN
CORROSION SET UP BY SM ALL R E LA TIV E
MOVEMENT OF PARTS WITH NO LUBRICATIO N.
REPLACE BEARING . CLEAN R ELATED PARTS.
CHECK SEALS AND CHECK FOR PROPER LUBRICATIO N.
HEAT
D I S C O L O R A T IO N
D IS C O L O R A T IO N
DISCOLORATION CAN RANGE FROM LIG H T BROWN
TO BLACK CAUSED BY INCORRECT LUB RICAN T OR
MOISTURE.
HEAT DISCO LO RATIO N CAN RANGE FROM FA INT
YELLOW TO D A R K BLUE RESULTING FROM OVER
LOAD (WAGON'S) OR INCORRECT LUBRICAN T.
RE-USE BEARINGS IF STAINS CAN BE REMOVED BY
LIG HT POLISHING OR IF NO EVIDENCE OF O VE R &shy;
HEATING IS OBSERVED.
EXCESSIVE HEAT CAN CAUSE SOFTENING OF RACES
OR ROLLERS.
CHECK SEALS A ND RELATED PARTS FOR DAMAGE.
TO CHECK FOR LOSS OF TEMPER ON RACES OR
ROLLERS A SIMPLE FILE TEST MAY BE MADE. A
FILE DRAWN OVER A TEMPERED PART W IL L GRAB
AND CUT M E TA L, WHEREAS, A FILE DRAWN OVER A
HARD PART W IL L G LID E R E A D ILY WITH NO M ETAL
CUTTING.
REPLACE BEARING S IF OVER HEATING DAMAGE IS
INDICA TE D. CHECK SEALS A ND OTHER PARTS.
SMEARS
SMEARING OF M E TA L DUE TO SLIPPAGE.
SLIPPAGE CAN BE CAUSED BY POOR FITS.
LU B R IC ATIO N , OVERH EATING , OVERLO ADS
OR H A N D LIN G DAMAGE.
REPLACE BEARINGS, CLEAN R ELATED PARTS
AND CHECK FOR PROPER FITS AND
LUBRICATIO N
Fig. 82—Differential and Axle Bearing Diagnosis Chart B
LIGHT DUTY TRUCK SERVICE MANUAL
REAR SU S P E N S IO N A N D DRIVELINE
4-41
SPECIAL TOOLS
13
■&lt;
14
r&gt;~V!\
../0
&quot;0 r
15
16
O
&quot;\
i
17
18
o
,,
19
20
21
1
22
23
24
lOW' R.G. AXLE ONLY
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
J-21548
J-23690
J-23689
J-21128
J-21057
J-22804-1
J-5748
J-6627
J-8092
J-5853
J-8614-II
J-2619
J-2222
J-24429
J-24433
T ru nnion Seal Installer
A xle S haft Bearing Installer
A xle S haft Bearing Remover
A xle S haft Seal Installer
Pinion O il Seal Installer
Pinion Seal Gauge Plate
Positraction Torque Measuring Adapter
Wheel B o lt Remover
Driver Handle
Torque Wrench - Inch/Pound
Companion Flange Holder
Slide Hammer
Wheel Bearing N ut Wrench
A djusting N ut Wrench
Pinion Rear Bearing Installer
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
J-24430
J-23322
J-24426
J-24432
J-24427
J-8608
J-24384
J-24428
J-24434
J-870
J-22380
J-22354
J-22281
J-8114
J-8093
D iffe re n tia l Side Bearing Installer
Pinion Straddle Bearing Installer
O uter Wheel Bearing Cup Tool
Pinion Rear Bearing Cup Installer
Inner Wheel Bearing Cup Installer
Outer Wheel Bearing Cup Installer
Pinion O il Seal Installer - Dana
Wheel Hub O il Seal Installer
Pinion O il Seal Installer - Chevrolet
Wheel Bearing N u t Wrench
T ru -A rc Pliers
Wheel O il Seal Installer
Pinion O il Seal Installer
Wheel Bearing O uter Cup Installer
Wheel Bearing Inner Cup Installer
Fig. 83—Special Tools
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5-1
SECTION 5
BRAKES
The following caution applies to one or more steps in the assembly
procedure of components in this portion of the manual as indicated at
appropriate locations by the terminology &quot;See Caution on page l of this
section.&quot;.
CAUTION: THIS FASTENER IS A N IMPORTANT ATTACHING
PART IN THAT IT COU LD AFFECT THE PE RF O R M A N C E OF
VITAL C O M P O N E N T S A N D SYSTEMS, AND/OR C OU LD RESULT
IN M A J O R REPAIR EXPENSE. IT M U S T BE REPLACED WITH
ON E OF THE S A M E PART N U M B E R OR WITH A N EQUIVALENT
PART IF REP LA C E M E N T B E C O M E S NECESSA R Y. D O N O T USE A
R E P L A C E M E N T PART OF LESSER QUALITY OR SUBSTITUTE
DESIGN. TORQUE VALUES M U S T BE USED AS SPECIFIED
DURING REASSE MB LY TO ASSURE PROPER RETENTION OF
THIS PART.
CONTENTS OF THIS SECTION
Standard Brakes................................................................................. 5-1
Power Brakes........................................................................................ 5-60
Special Tools........................................................................................ 5-70
STANDARD BRAKES
INDEX
General Description............................................................
Master Cylinder..................................................................
Combination Valve...........................................................
Disc Brakes Front..............................................................
Drum Brakes R ear............................................................
Theory of Operation..........................................................
Hydraulic System...............................................................
Pressure and Force............................................................
Brake System Components.............................................
Operation of Brake Mechanism..................................
Front Disc Brakes...........................................................
Rear Drum Brakes.........................................................
Maintenance and Adjustment..........................................
Brake Inspection.................................................................
Hydraulic Brake Fluid.....................................................
Bleeding Hydraulic System.............................................
Pressure Bleeding.............................................................
Manual Bleeding.............................................................
Hydraulic Brake Lines and Tubing............................
Drum Brake Adjustment.................................................
Brake Pedal Free Travel Adjustment........................
Stoplamp Switch Adjustment........................................
Brake Travel Warning Switch......................................
5-2
5-2
5-2
5-2
5-2
5-4
5-4
5-5
5-5
5-10
5-11
5-12
5-15
5-15
5-16
5-16
5-16
5-17
5-18
5-21
5-22
5-22
5-22
Parking Brake Adjustment...............................................5-22
Parking Brake (Propeller Shaft) Adjustm ent......... ..5-23
Component Replacement and R ep air......................... ..5-24
Shoes and Linings—Rear Drum Brakes.................... ..5-24
Anchor Pin Replacement..................................................5-27
Wheel Cylinder.....................................................................5-27
Brake Drum Refinishing...................................................5-28
Shoe and Linings—Front Disc Brakes....................... ..5-29
Caliper Overhaul..................................................................5-31
Disc Refinishing...................................................................5-34
Master Cylinder....................................................................5-36
Master Cylinder Overhaul................................................5-36
Master Cylinder (with Frame Mounted Booster)... 5-38
Bench Bleeding Master Cylinder...................................5-39
Brake Combination Valve.................................................5-40
Brake Travel Warning Switch...................................... ..5-41
Brake Pedal-Service Brake..............................................5-42
Parking Brake Pedal........................................................ ..5-42
Parking Brake Cables...................................................... ..5-43
Parking Brake-Propeller S haft.................................... ..5-43
Rear Brakes—R.P.O. H-22................................................5-46
Diagnosis...................................................................................5-48
Inspection................................................................................5-48
Preliminary Checks..............................................................5-49
Road Testing....................................................................... ..5-49
LIGHT DUTY TRUCK SERVICE MANUAL
5-2 BRAKES
GENERAL DESCRIPTION
All vehicles are equipped with a dual hydraulic brake
system.
The split system consists basically of two separate brake
systems. When a failure is encountered on either, the
other is adequate to stop the vehicle. If one system is not
functioning, it is normal for the brake pedal lash and
pedal effort to substantially increase. This occurs because
of the design of the master cylinder which incorporates
an actuating piston for each system. When the rear
system loses fluid, its piston will bottom against the front
piston. When the front system loses fluid, its piston will
bottom on the end of the master cylinder body. The
pressure differential in one of the systems causes an
uneven hydraulic pressure balance between the front and
rear systems. The combination valve, near the master
cylinder, (except RPO H22 vehicles) detects the loss of
pressure and illuminates the brake alarm indicator light
on the instrument panel. The pressure loss is felt at the
brake pedal by an apparent lack of brakes for most of
the brake travel and then, when failed chamber is
bottomed, the pedal will harden.
RPO H22 vehicles (with frame mounted vacuum over
hydraulic boosters) have an electrical switch that senses
pedal travel. This switch will illuminate the lamp on the
instrument panel whenever the brake pedal travel is in
excess of 5.10 inches.
If a vehicle displays these symptoms, it is a good
indication that one of the systems contains air or has
failed, and it is necessary to bleed or repair the brakes.
MASTER CYLINDER (Fig. 1)
The system is designed with a separate hydraulic system
for the front and rear brakes using a dual master
cylinder. The cylinder has two separate reservoirs and
outlets in a common body casting. On all 10 and G20
series vehicles, the front reservoir controls the front
brake system and the rear reservoir controls the rear
system. On all other 20-30 series vehicles, the front
reservoir controls the rear brake system and the rear
reservoir controls the front system (except on CA 30 with
vacuum over hydraulic boosters where the front is
controlled by the front booster and rear by the rear
booster).
COMBINATION VALVE
All models (except models with vacuum over hydraulic
boosters) have a combination valve. The combination
valve is located below the master cylinder on P and G
models; on the front crossmember on C-K models. The
front and rear hydraulic lines are routed through this
combination &quot;metering&quot; and &quot;brake failure warning
switch&quot; to their appropriate wheel cylinders or caliper.
The metering portion of the combination valve tends to
&quot;hold off&quot; front hydraulic pressure until the rear brake
system overcomes their pull back springs; then pressure
is allowed to flow with the result being a good
distribution of braking effort.
The brake failure warning switch portion of the
combination valve &quot;senses&quot; a loss of hydraulic pressure,
if a failure should occur and turns &quot;on&quot; a red light in
the dash to warn the operator of the failure.
DISC BRAKES FRONT—(Fig. 2)
All models have disc brakes on the front. The one piece
caliper mounts on the steering knuckle/steering arm,
which is also a one piece casting, and astride the brake
disc. The caliper is the single piston design which is said
to be a sliding caliper sliding piston. No front brake
adjustment is necessary once the system is in operation
and the pedal has been stroked to &quot;seat&quot; the shoes to the
caliper.
DRUM BRAKES REAR—(Fig. 3)
The rear brakes are duo servo and self adjusting (except
R.P.O. H-22). Brake adjustment takes place when the
brakes are applied with a firm pedal effort while the
vehicle is backing up. Applying the brakes moves the
actuator which turns the star wheel and lengthens the
adjuster screw assembly. This action moves the shoes
outward until clearance between the lining and drum is
within proper limits.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5-3
P105 ( 42)
P300 ( 32)
C-K MODELS
P300 ( 42)
WITH RPO H22/H23
G MODELS
P MODELS
Fig. 1-Master Cylinder Mountings- Typical
LIGHT DUTY TRUCK SERVICE MANUAL
5 -4 BRAKES
Fig. 3--Rear Drum Brake
Fig. 2--Front Disc Brake
THEORY OF OPERATION
Brakes are simply a means of applying friction to either
stop, slow down or hold an element. Brakes accomplish
their job by converting motion energy, or kinetic energy,
to heat energy, through brake shoes and linings.
On the present day vehicle, the brake shoes are metal
with heat resistant linings attached. The brake shoes are
applied against the brake drum or disc by hydraulic
pressure.
To perform properly, the brake components must be
properly installed and adjusted.
First, the drum or disc must be the right size and shape,
diameter, width, thickness and contour to provide
enough friction area and adequate heat dissipation.
Second, the linings must be of the correct material, size
and contour to provide the proper amount of friction
for:
a. Proper performance
b. Satisfactory durability
c. Freedom from noise and scoring
Third, clearances must be correct.
Fourth, the operating system must be simple, dependable
and easily adjusted.
The basic hydraulic brake system consists of (1) a master
cylinder, in which the hydraulic pressure is developed,
(2 ) a cylinder at each wheel, where hydraulic pressure is
utilized to force linings to rub against a brake disc or
brake drum, and (3) the necessary tubing and flexible
hoses to connect the master cylinder to the wheels. Of
course, we need a method of generating this hydraulic
pressure so we have a pedal mounted within the vehicle
and connected to the master cylinder through a push rod.
The principle of hydraulic pressure is put to work
through the use of the pedal.
When the pedal is depressed the master cylinder piston
HYDRAULIC SYSTEM (Fig. 4)
When fluid is contained in a closed system and pressure
is applied to it, the pressure is exerted equally in all
directions (Pascal’s Law). By applying this law, we are
able to have a brake system that is easy to maintain and
functionally stable.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
is pushed forward. The fluid in the master cylinder, and
the entire system, being incompressible, transmits the
force exerted by the master cylinder piston to all the
inner surfaces of the system. At this point only the
pistons in the wheel cylinders or caliper are free to move,
and since the hydraulic fluid is not compressible, the
pistons move outward to force brake shoes against the
brake drums or disc.
To work properly a hydraulic brake system must be
leakproof, sturdy and filled with the right type of fluid.
The right type of fluid is one that has no corrosive effect
on the system’s parts, and does not readily freeze, boil or
vaporize at the temperature extremes encountered in
vehicle use.
PRESSURE AND FORCE (Fig. 5)
One of the advantages of a hydraulic system is that we
have the same pressure inside the system and up to all
wheels. This does not mean however that we are
applying the same force at each wheel; in fact, it permits
us to apply unequal force under certain circumstances.
NOTE: Pressure may be different at front or
rear wheels due to valving. Valves are
covered later in this section.
Pressure can be defined as the amount of force applied
to a specific area, (measured in square inches). Suppose a
hydraulic pressure of 10 psi (pounds square inch) were
applied to an object with a surface area of 16 square
inches. The total applied force would equal 160 pounds (ten psi pressure times an area of 16 square inches). If
the same 10 psi were applied to an object with a surface
area of two square inches, a force of 20 pounds would be
applied.
Reduced to a formula, this means that pressure (in
pounds per square inch) times area (in square inches)
equals total force applied.
10 psi
PRESSURE GAUGE
AREA—16 sq. in.
AREA—2 sq. in.
5-5
This is the principle that enables us to incorporate a very
desirable feature in the brake system - we can vary the
braking power to the wheels by changing the wheel
cylinder piston area.
Some of the vehicle weight is transferred to the front
wheels when the brakes are applied. We can balance this
weight transfer with different braking force at the front
and rear wheels.
BRAKE SYSTEM COMPONENTS
MASTER CYLINDER (Fig. 6)
The master cylinders used today have split reservoirs.
This means that the front and rear brakes are separated
from each other by the design of the master cylinder.
The master cylinder contains two fluid reservoirs and two
cylindrical pressure chambers in which force, applied to
the brake pedal, is transmitted to the fluid which actuates
the brake shoes. Breather ports and compensating ports
permit passage of fluid between each pressure chamber
and its fluid reservoir during certain operating
conditions. A vented cover and flexible rubber
diaphragm, at the top of the master cylinder reservoir,
seal the hydraulic system from possible entrance of
contamination while at the same time permitting
expansion or contraction of fluid within the reservoirs
without direct venting.
In the pressure chambers, coil springs hold rubber
primary seals against the end of the pistons. These seals
and rubber secondary seals on the opposite end of the
pistons, prevent escape of fluid past the pistons. The
piston is retained in the cylinder by a push rod retainer.
A rubber boot is installed over this end of the cylinder to
exclude foreign matter.
Stroking or pushing the brake pedal causes the primary
piston in the master cylinder to move forward. At the
same time, a combination of hydraulic pressure and
force of the primary piston spring moves the secondary
piston forward. When the pistons have moved forward
so that their primary seals cover the compensating ports,
hydraulic pressure is built up and transmitted to the
front and rear wheels.
When the brake pedal is released, the master cylinder
pistons move rearward and hydraulic pressure on the
brake system is released.
Rear Line Failure (Fig. 7)
160
POUNDS
10 x 16 Sq. in. = 160 lbs.
(psi) x (AREA)= TOTAL FORCE
10 x 2 sq. in. = 20 lbs.
(psi) x (AREA) = TOTAL FORCE
Fig. 5 -Pressure and Force
In case of a ruptured rear brake line or some other
malfunction, the primary piston will move forward when
the brakes are applied, but will not generate hydraulic
pressure. Only a negligible force is transferred to the
secondary piston through the primary piston spring until
the primary piston comes in contact with the secondary
piston. Then, push rod force is transmitted directly to the
secondary piston and sufficient pressure is generated to
operate the front brakes.
LIGHT DUTY TRUCK SERVICE MANUAL
5-6 BRAKES
COVER RETAINING BAIL
RUBBER DIAPHRAM
RESERVOIR COVER
Fig. 6--Master Cylinder
u q ljq l:
f=&pound;.
SECONDARY
PISTON
PRIMARY
PISTON
^vTT
Hj&reg;.
Jc
A
frontA
V ^ brakesv
^ J
Fig. 7- Rear Line Failure
Front Line Failure (Fig. 8)
If there is a malfunction in the front brake line, both
pistons will move forward when the brakes are applied,
as under normal conditions. However, due to the front
line malfunction, there is nothing to resist piston travel
except the secondary piston spring. This permits the
primary piston to generate only negligible pressure until
the secondary piston bottoms in the cylinder bore. Then,
Fig. 8 -Front Line Failure
sufficient hydraulic pressure will be generated to operate
the rear brakes.
It should be noted that if either the front or rear brakes
become inoperative, one brake system will remain
effective and permit the vehicle to be brought to a
controlled stop. Increased pedal travel will be evident as
well as increased pedal force since only a part of the
normally available braking surface will be used. Both of
these effects should be noticeable to the driver but, as an
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
added safety feature, a warning light has been
incorporated into the brake system. The dash-mounted
warning light will come on when the brakes are applied
under a condition of partial failure. This is a signal to
the driver to have the brakes serviced.
WHEEL CYLINDER (Fig. 9)
Each wheel cylinder contains two pistons and two rubber
cups which are held in contact with the pistons by a
central coil spring with cup expanders to provide a fluidtight seal. The wheel cylinder cups are of a special heat
resisting rubber. Cups of this material must have an
expander to hold the lips of the cup out against the
wheel cylinder bore. These cup expanders are crimped
on each end of the wheel cylinder spring.
The inlet port for brake fluid is located between the
pistons so that when fluid pressure is applied, both
pistons move outward toward the ends of wheel
cylinders. The pistons impart movement to the brake
shoes by means of connecting links which seat in the
pistons and bear against webs of the shoes. Rubber boots
enclose both ends of the cylinder to exclude foreign
matter. A valve for bleeding the brake lines and wheel
cylinder is located above the inlet port.
COMBINATION VALVE (Fig. 10)
The combination valve is just what its name implies. The
metering valve, failure warning switch and proportioner
are &quot;combined&quot; into an assembly which also serves as
the front junction block. This valve is used on all disc
brake applications. The input-output characteristics of
the valve (i.e. split points), vary with vehicle usage.
PUSH ROD AN D BOOT
PISTON
CUP RETURN SPRING WITH EXPANDERS
WHEEL CYLINDER HOUSING
PISTON CUP
PISTON CUP
BLEEDER SCREW
' ig F * ------- PISTON
&amp;
PUSH ROD AND BOOT
Fig. 9- Typical Wheel Cylinder
5-7
Metering Valve
The Metering Valve &quot;holds-off&quot; front disc braking until
the shoes of the rear drum brake contacts the drum.
Brakes Not Applied (Fig. 11)
The metering valve allows free flow of brake fluid
through the valve when the brakes are not applied. This
allows the fluid to expand and contract with temperature
changes. (The boot is pressed in, to hold the pin down
during bleeding operations.)
Shut-Off Point-Initial Brake Apply (Fig. 12)
The metering valve stem moves to the left, and at 4 to 30
psi, the smooth end of the stem is in a sealing position
with the metering valve seal lip and this is the shut-off
point.
Hold-Off Blend Pressure (Fig. 13)
The metering valve stem continues to the left on initial
brake apply and stops on the knurl at the metal retainer.
The metering valve spring holds the retainer against the
seal until a predetermined psi is produced at the inlet of
the valve. This pressure overcomes the spring and allows
pressure through the valve to the front brakes. The
continued increase of pressure into the valve is metered
through the metering valve seal, through to the front
brakes and produces an increasing force on the
diaphragm. The diaphragm pulls the pin and the pin in
turn pulls the retainer, thus reducing the spring load on
the metering valve seal. Eventually, the pressure reaches
the point where the spring is completely pulled away by
the diaphragm pin and retainer leaving the metering
valve seal free to pass unrestricted pressure through the
valve.
Failure Warning Switch (Fig. 14)
The Failure Warning Switch is activated if either front
or rear brake systems fail, and when activated, completes
a circuit to the dash warning lamp. If the rear hydraulic
system fails, the pressure of the good front system forces
the switch position to the right. The switch pin is forced
up into the switch by the piston ramp and makes the
electrical circuit lighting the dash lamp, and is held in
this position by the piston. When repairs are made and
pressure is returned to the rear system by bleeding, the
piston moves to the left and resets the switch to the off
position. The detent on the piston typically requires 100
to 450 psi pressure before allowing full reset (centering)
of the piston. The same condition will exist if the front
hydraulic system fails except the piston moves to the left.
Proportioner
The rear brake Proportioner improves front-to-rear
brake balance at high deceleration. During high
deceleration stops, a percentage of the rear weight is
transferred to the front wheels. Compensation must be
made for the resultant loss of weight to the rear wheels
to avoid early rear wheel skid. The proportioner part of
LIGHT DUTY TRUCK SERVICE MANUAL
5 -8 BRAKES
SWITCH TERMINAL
SWITCH PIN
FRONT INLET PORT-^ SWITCH PISTON
DETENT
,REAR INLET PORT
PROPORTIONER PISTON
VALVE STEM
FRONT OUTLET
PORT
STOP PLATE
BOOT
PROPORTIONING NUT'
REAR OUTLET PORT
DIAPHRAGM
'METERING VALVE SEAL
FRONT OUTLET PORT
METERING VALVE STEM
Fig. 10--Combination Valve
FROM MASTER CYLINDER
Fig. 11 -Brakes Not Applied
the combination valve reduces the rear brake pressure
and delays the rear wheel skid.
Normal Brake Stops (Fig. 15)
The proportioner does not operate during normal brake
stops. Fluid normally flows into the proportioner,
through the space between the piston center hole and
valve stem, through the stop plate and out to the rear
brakes. The spring loads the piston so that it rests
against the stop plate for normal brake pressures.
Fig. 1 2 -Shut-Off Point
Proportioning Action (Fig. 16)
Pressure developed within the valve pushes against the
large end of the piston and when sufficient to overcome
the spring load, moves the piston to the left. The piston
&quot;Contacts&quot; the spherical stem seat and starts proportion&shy;
ing by restricting pressure through the valve.
Overhaul and Major Service
The combination valve is not reparable. If a defect is
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5-9
FROM MASTER CYLINDER REAR OUTLET
Fig. 13--Hold-Off and Blend Pressure
Fig. 14 -Rear System Failure
found in any portion of the valve, the complete valve
assembly must be replaced.
BRAKE TRAVEL WARNING SWITCH (FIG.
17)
Vehicles with frame mounted vacuum over hydraulic
boosters have an electrical switch that senses pedal
travel. This switch will illuminate the lamp on the
instrument panel whenever the brake pedal travel is in
excess of 5.10 inches.
BRAKE STOPLAMP SWITCH
The brake stoplamp switch is mounted on a flange
protruding from the brake pedal support bracket below
the instrument panel (fig. 18). When the brake pedal is
depressed, the switch plunger (which is spring loaded),
follows the brake pedal arm downward until the switch is
in the &quot;O N &quot; position. When the brake is released, the
brake pedal arm returns the switch plunger to the
&quot;O FF&quot; position.
BRAKE PEDAL
The brake pedal is a lever, pivoted at one end, with the
master cylinder push rod attached to the pedal near the
pivot point. By this lever arrangement the force applied
to the master cylinder piston through the push rod is
multiplied several times over the force applied at the
brake pedal (fig. 19).
Proper service of the brake pedal is vital to good brake
performance, and pedal operation should be checked
each time brakes are inspected. Weak or broken return
springs or lack of lubrication can cause sluggish release
LIGHT DUTY TRUCK SERVICE MANUAL
5 -1 0 BRAKES
of the brakes. Wear in the pedal linkage, pivot pins, or
bushings, can cause loss of pedal or frequent need for
brake adjustment. Pedal free play is the free travel of
the pedal before any movement of the master cylinder
piston occurs. Too little free play can cause brakes to
drag. Too much free play may result in a low pedal. The
free play at the brake pedal pad should be l / 16 to 1/4
inch for the standard height pedal.
OPERATION OF BRAKE
MECHANISM
When the brakes are fully released, the master cylinder
pistons are held against the push rod retainer, and the
primary seals are held just clear of the compensating
C O N T A C T IS MADE
Fig. 18-Stoplamp Switch (Typical)
Fig. 19-Brake Pedal (Typical)
ports by the piston springs. The pressure chambers are
filled with fluid at atmospheric pressure due to the open
compensating ports and the flexible reservoir diaphragm.
When the brake pedal is depressed to apply the brakes,
the push rod forces the master cylinder pistons and
primary seals forward. As this movement starts, the lips
of the primary seals cover the compensating ports to
prevent escape of fluid into the reservoirs. Continued
movement of the pistons builds pressure in the pressure
chambers and fluid is then forced through the lines
leading to the wheel cylinders. Fluid forced into the
wheel cylinders between the cups and pistons causes the
pistons and connecting links to move outward and force
the brake shoes into contact with the drums.
Movement of all brake shoes into contact with drums is
accomplished with very light pedal pressure. Since
pressure is equal in all parts of the hydraulic system,
effective braking pressure cannot be applied to any one
drum until all of the shoes are in contact with their
respective drums; therefore, the system is self-equalizing.
When the brake pedal is released, the master cylinder
springs force the pedal back until the push rod contacts
the retaining ring in the master cylinder. This spring
also forces the pistons and primary seals to follow the
push rod.
At the start of a fast release, the pistons move faster
than the fluid can follow in returning from the lines and
wheel cylinders; therefore, a partial vacuum is
momentarily created in the pressure chamber. Fluid
supplied through the breather ports is then drawn
through the bleeder holes in piston heads and past the
primary seals to keep the pressure chamber filled.
As pressure drops in the master cylinder, the shoe
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
springs retract all brake shoes and the connecting links
push the wheel cylinder pistons inward, forcing fluid
back to the master cylinder. With the piston bearing
against the retaining ring and the lips of the primary
seals just clear of the compensating ports, excess fluid
which entered through the bleeder holes or was created
by expansion due to increased temperature, now returns
to the reservoirs through the uncovered compensating
ports.
SINGLE PISTON FRONT DISC BRAKES (Fig.
20)
When fluid is contained in a closed system and pressure
is applied to it, this pressure is exerted equally in all
directions (fig. 4). In the single piston mechanism,
hydraulic pressure acts on two surfaces.
The first, and most obvious, is the piston. The second is
in the opposite direction against the bottom of the bore
of the caliper housing. Since the area of the piston and
bottom of the caliper bore are equal, equal forces are
developed.
Hydraulic force in the caliper bore is exerted against the
5-11
piston which is transmitted to the inner brake shoe and
lining assembly and the inner surface of the disc. This
tends to pull the caliper assembly inboard, sliding on the
four rubber bushings. The outer lining, which rests on
the caliper housing, then applies a force on the outer
surface of the disc and together the two linings brake the
car. Since an equal hydraulic force is applied both to the
caliper housing and the piston, the force created against
the outer surface of the disc is the same as the inner.
Since there are equal forces on the linings, no flexing or
distortion of the disc occurs regardless of the severity or
length of application, and lining wear will tend to be
equal.
Note the running clearance of the brake shoe and the
brake disc in Figures 21 and 22. When the brake pedal is
depressed, the piston being in contact with the other side
of the brake shoe, applies force to the inner surface of
the disc. This force causes the caliper to move inboard
until an equal force is applied to the outer disc surface.
The movement that takes place is very slight and would
have to be observed very closely to be seen.
As the brake linings wear, the caliper assembly moves
inboard and fluid fills the area behind the piston, so that
Fig. 20--Disc Brake Operation
LIGHT DUTY TRUCK SERVICE MANUAL
5 -1 2 BRAKES
there is not a condition of pedal travel increase with
respect to the front brake as the linings wear (fig. 21 ).
As the driver releases the brake pedal, it is important
that the piston immediately release from the shoe and
lining. As pointed out earlier, the movement from no
application to full application is very slight, therefore it
should be easy to understand that as force is removed,
the piston and caliper merely relax into the released
position and braking effort is removed.
An important thing to remember about disc brakes is
that the lining is in constant contact with the disc (fig.
21 ) giving the added advantages of improved brake
response, reduced pedal travel and faster generation of
line pressure. The shoe, being at zero clearance, also
&quot;wipes&quot; the disc free of any foreign matter. Disc brakes
also have good fade resistance with fast recovery.
The major components of the single piston sliding
caliper disc brake are the hub and disc assembly, the
shield, the support, the caliper assembly, and the shoe
and lining assemblies (fig. 22). The cast iron disc is of
the fully ventilated design. Note that between the
machined braking surfaces are cooling fins. This design
acts to cool the brakes by fanning the air and in addition
has many cooling surfaces.
Hub and Disc
The purpose of the disc is to provide the frictional
surfaces required to stop the vehicle.
Shield and Support
The disc is protected from cross vehicle splash by a
shield on the inboard side that is bolted to the steering
knuckle.
Brake Caliper
NEW
WORN
Fig. 21- New and Worn Linings
The caliper provides a means of applying the shoe and
lining assemblies to the disc. It is connected to the system
by a hydraulic line. It is mounted to the support plate by
two housing retainer bolts, two sleeves and four rubber
bushings. An inner caliper rubber bushing is installed
between each sleeve and groove in the housing, and an
outer caliper rubber bushing is installed between each
bolt and groove in the housing. Shoe and lining
assemblies are positioned on the caliper so they straddle
the disc.
REAR DRUM BRAKES (Fig. 2 3 )
The entire rear wheel brake mechanism is mounted on
the brake flange plate, which is bolted directly to the axle
housing (fig. 23).
PULL BACK SPRINGS
PRIMARY SHOE
FWD&quot;*'
SECONDARY
SHOE
ACTUATING LEVER
Fig. 22- Disc and Caliper - Single Piston
HOLD DO W N
SPRING
A N D PIN
Fig. 23-Rear Drum Brake - Right Side Shown
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
The anchor pin is the upper pivot point of the brake
shoes. It is located above the wheel cylinder, and is
secured to the top of the flange plate.
Two brake shoes are used, a primary shoe toward the
front of the vehicle, and a secondary shoe toward the
rear. Brake shoe linings are secured to the shoes. The
primary shoe lining is shorter than the secondary shoe
lining.
The shoes are fitted to the anchor pin at the top and
secured by color-coded retracting springs. At the bottom
they fit into grooves at each end of the star wheel
adjuster and are retained in position by a primary to
secondary connecting spring located above the star wheel
adjuster. Each shoe is also attached to the flange plate by
means of a hold-down pin, which is retained in position
by a hold-down spring and retainer cup.
The star wheel assembly is installed under the primary to
secondary shoe connecting spring. A self-adjusting brake
shoe mechanism consisting of a link, actuating lever,
pawl and pawl return spring is also used. The loop end
of the link is attached to the shoe guide plate and the
hooked end to the actuating lever.
Self Energizing Action (Fig. 24)
The brakes are self-energizing. This means that the
brake unit is designed to assist the driver in forcing the
shoes against the drum. To see how this is done, let’s
observe a step-by-step sequence of brake action.
When pressure is applied to the brake pedal, fluid is
delivered under pressure from the master cylinder to
each of the wheel cylinders. At each wheel cylinder the
fluid forces the two pistons outward in the bore. This
motion is transmitted from the piston to the shoes by
thrust rods or &quot;struts&quot;.
This action forces the shoes outward at the top causing
the shoes to pivot on the adjusting screw assembly (as the
shoes move outward, they also stretch the pull-back
5-13
springs which are used later to return the shoes to the
rest position).
When the shoes expand outward, they contact the drum
and tend to rotate with the drum. It is this principle that
allows the self-energizing feature to exist. The primary
shoe (the first shoe from the anchor pin in the direction
of normal rotation), rotating with the drum, moves away
from the anchor pin and exerts a rearward force on the
adjusting screw.
At the same time this is taking place the secondary shoe
is rotating upward until the shoe web contacts the anchor
pin.
We can then see that the force applied to the secondary
shoe is the sum of the apply force on the primary shoe
and the force caused by rotation (friction force) of the
primary shoe. This combination of force is the selfenergizing feature, and the increased force it applies to
the brake shoes results in less physical effort required at
the brake pedal.
The increased braking force applied to the secondary
shoe accounts for the fact that the secondary shoe lining
area is usually larger than that of the primary shoe
lining.
When the brakes are applied with the vehicle moving in
reverse, the rear shoe becomes, in effect, the primary
shoe. The self-energizing action now would be applied to
the front shoe, and the rear shoe would move away from
the anchor pin.
Self-Adjusting Action
With the understanding of the operation of the drum
brake system, we can apply the same step-by-step
sequence to see how the self-adjusting mechanism
operates. In the component description given earlier, we
found that the actuating lever assembly of the selfadjusting mechanism is mounted on the secondary or
rear shoe.
The lever is attached to the web of the secondary shoe by
the hold down pin and spring. The deep dished washer,
used as the hold down spring seat, passes through the
lever and into the shoe web. Thus, the lever is allowed to
pivot about this point. Also, this spring type mount keeps
the pawl end of the lever in firm contact with the teeth
of the adjusting screw star wheel.
Forward Stops (Fig. 25)
Fig. 24- Brake Operation
During a forward stop, the shoes expand outward and
contact the drum; they rotate with the drum until the
secondary or rear shoe contacts the anchor pin. Thus the
pivot point for the secondary shoe moves only far
enough to place the lining in contact with the drum.
Subsequent motion is then in the direction of the anchor
pin. When the brakes are released, the secondary shoe is
already in contact with the anchor pin, so its only
movement is to pivot on the anchor pin, and follow the
primary shoe to the rest position. Now, let’s see what
affect the forward stop has on the self-adjusting
LIGHT DUTY TRUCK SERVICE MANUAL
5 -1 4 BRAKES
slight amount of movement is not enough to cause the
actuating lever to advance the star wheel.
Over-Ride Mechanism (Fig. 27)
PR IM AR Y S H O E
MOVES A W A Y
FR O M A N C H O R
PIN
Fig. 25--Reaction During Forward Stop
mechanism. First, the small amount of movement from
the rest position until the shoes contact the drum, is
permitted without activating the adjusting mechanism by
the slack inherent to this linkage design. Since the
rotation of the secondary or rear shoe is toward the
anchor pirr, the effective distance from the pin to the
actuating lever is not increased; thus, no adjustment
occurs. When the brakes are released, the linkage relaxes
with any small degree of motion absorbed by the linkage
slack.
Reverse Stops (Fig. 26)
During a reverse stop, the shoes expand outward to
contact the drum, and then rotate with the drum until
the primary or front shoe contacts the anchor pin. When
there is sufficient clearance between the lining and the
drum, this rotation increases the distance from the
anchor pin to the secondary or rear shoe hold down pin.
Since the wire link between the anchor pin and actuating
lever is a fixed length, the movement of the lever pivot
point causes the top of the actuating lever to be pulled
inward. As the lever pivots on the hold down spring cup,
the pawl end rocks down on the adjusting screw star
wheel. When the pawl turns the star wheel, it increases
the length of the adjusting screw in much the same
manner as a service technician using a brake adjusting
tool.
As the lever rocks down to turn the star wheel, it also
moves outboard to follow the contour of the star wheel.
At the same time, the downward motion compresses the
lever return spring. When the brakes are released, the
pull-back springs return the shoes to their normal
position, the lever return spring raises the pawl end of
the lever back to its normal position. The pawl slips back
over the teeth of the star wheel and takes a new &quot;bite&quot;
on another notch.
When there is only a slight clearance between the shoes
and drums, such as the condition when the brakes are
near to proper adjustment, the shoes rotate only a small
amount before the shoes contact the anchor pin. This
All of the standard equipment self-adjusting mechanisms
contain a built-in safety device known as the &quot;over-ride
pivot plate and spring&quot;. This pivot plate and spring are
mounted on the upper end of the actuating lever, acting
as a semi-rigid connection between the actuating lever
and the wire link. The over-ride mechanism has one
major function; to prevent damage to the linkage when,
for some reason, the linkage cannot move as dictated by
shoe rotation. Two common examples of this condition
occurs when; the adjusting screw binds, or the brakes are
severely out of adjustment.
If the adjusting screw threads should bind, the selfadjusting mechanism would attempt to continue
operating. This would result in damaged parts, or
possible reduced brake application on the affected wheel.
When this occurs, the actuating lever remains stationary,
and the over-ride pivot plate is pulled by the wire link.
This motion is absorbed by stretching the over-ride
spring. With the adjusting motion dampened by the
spring, the component parts remain undamaged.
NOTE: One symptom of a bound adjusting
screw is &quot;pulling brakes&quot;. Inspect the screw
when a complaint of brake pull is reported.
The second purpose of the over-ride plate is to prevent
excessive actuating lever travel. This condition could
occur if the brake adjustment were extremely loose.
Should this condition occur, the motion of the actuating
lever could allow the pawl end to rock down until it
contacted the secondary shoe. Here again, without the
over-ride spring, linkage damage or reduced brake
efficiency could result.
Equally important to proper brake adjustment is the
prevention of adjusting screw &quot;back-off&quot;. The selfenergizing force transmitted by the adjusting screw tends
to compress the screw length. We can thus see the
REVERSE
S E C O N D A R Y SH O E
M OVES A W A Y
FR O M
A N C H O R PIN
FIXED LEN G TH
O F W IRE LIN K
C AUSES LEVER
T O P IV O T
Fig. 26--Reaction During Reverse Stop
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5-15
STOP TANG
SEATED ON
SHOE
Fig. 27 Override Component Operation
necessity of preventing star wheel &quot;back-off&quot; during the
maximum self-energizing condition. To do this, a &quot;stop
tang&quot; extends down from the under side of the actuating
lever to contact the secondary shoe (fig. 28). This limits
the actuating lever travel to a maximum of three notches
per stroke, which has the effect of maintaining pawl
engagement to the star wheel while braking to a stop.
Again, as in the case of a bound adjusting screw, any
additional shoe motion is absorbed by the over-ride
pivot plate and spring.
NOTE: The actuating lever stop is also the
mount and guide for the lever return spring.
The actuating lever is held against the secondary shoe by
the hold-down spring and cups. The pawl is connected to
the actuating lever and held in position by the pawl
return spring.
Fig. 28-Actuating Lever Stop Tang
Parking Brake Activating Mechanism
The activating mechanism for the parking brake consists
of an operating lever located in back of the secondary
shoe, and attached to the shoe by a pivot at the upper
end. A strut rod located a few inches below the pivot
point, extends forward from this lever to the primary
shoe.
The parking brake cable is connected to the lower end of
the operating lever. When the parking brake is applied,
the cable pulls the lower end of the operating lever
forward, causing the strut rod to push the primary shoe
forward. At the same time, the upper end of the lever
pushes the secondary shoe rearward. The combined
action of the lever and the strut rod drives the primary
and secondary shoes apart and into contact with the
drums.
M A IN TEN A N C E A N D ADJUSTMENTS
BRAKE INSPECTION
Every 12 months or 12,000 miles-whichever occurs first:
Inspect drum brake linings or disc brake pads, as well as
the other internal brake components at each wheel
(drums, rotors, wheel cylinders, etc.). For convenience, it
is recommended that disc brake pads be checked
whenever tires are rotated (at 6000 mile intervals). More
frequent checks should be made if driving conditions
and habits result in frequent brake application. Parking
brake adjustment should also be checked whenever brake
linings are checked.
NOTE: During any inspection period, the
remaining lining life expectancy should be
determined. This determination should dic&shy;
tate the next inspection period.
Lining Inspection
Drum Brake
Replace whenever the thickness of any part of any lining
is worn to within 1/32&quot; of the shoe table or rivet head
whichever is applicable.
Another important point to remember, always replace
brake shoes in axle sets (right and left side).
Disc Brakes
Check both ends of the outboard shoe by looking in at
each end of the caliper. These are the points at which the
highest rate of wear normally occurs. However, at the
same time, check the lining thickness on the inboard
shoe to make sure that it. has not worn prematurely.
Replace whenever the thickness of any part of any lining
LIGHT DUTY TRUCK SERVICE MANUAL
5 -1 6 BRAKES
is worn to within 1/32&quot; of the shoe or rivet whichever is
applicable.
HYDRAULIC BRAKE FLUID
Brake fluid is a specially blended liquid which provides a
means of transmitting hydraulic pressure between the
master cylinder and the brake calipers and wheel
cylinders. Brake fluid is one of the most important parts
of the hydraulic system. Use GM Hydraulic Brake Fluid
Supreme No. 11 or DOT-3, meeting GM Specification
GM4653M or equivalent.
Brake fluid must have certain specific qualities such as:
1. Viscosity (free flowing at all temperatures).
2. High boiling point (remain liquid at highest
operating temperatures).
3. Non-corrosive (must not attack metal or rubber
parts).
4. Water tolerance (must be able to absorb and retain
moisture).
5. Lubricating ability (must lubricate piston and seals
to reduce wear and internal friction).
6 . Low freezing point (must not freeze even at lowest
operating temperatures).
If brake fluid becomes contaminated, it may lose some
of its original qualities. It is good practice to bleed the
brake system until all old fluid is removed when
performing major brake work. Old fluid should be bled
from the system and replaced with clean brake fluid if
any of the hydraulic system parts are corroded or the
fluid is discolored or dirty. If any of the rubber parts of
the hydraulic system are soft or swollen old fluid should
be removed and hydraulic system should be flushed with
clean brake fluid. Do not reuse old brake fluid at any
time.
In the event that improper fluid has entered the system,
it will be necessary to service the system as follows:
1. Drain the entire system.
2. Thoroughly flush the system clean with brake fluid.
CAU TIO N: Use only brake fluid when flushing
3.
a system.
Replace all rubber parts of the system, brake hoses
and combination valve.
4. Refill the system.
5. Bleed the system.
Flushing Brake Hydraulic System
It is recommended that the entire hydraulic system be
thoroughly flushed with clean brake fluid whenever new
parts are installed in the hydraulic system.
Flushing is also recommended if there is any doubt as to
the grade of fluid in the system or if fluid has been used
which contains the slightest trace of mineral oil.
Flushing is performed at each bleeder valve in turn, and
in the same manner as the bleeding operation except
that bleeder valve is opened 1- 1/2 turns and the fluid is
forced through the lines and bleeder valves until it
emerges clear in color. Approximately one quart of fluid
is required to flush the hydraulic system thoroughly.
When flushing is completed at all bleeder valves, make
certain the master cylinder reservoir is filled to proper
level.
BLEEDING HYDRAULIC SYSTEM
The hydraulic brake system must be bled whenever, any
line has been disconnected or air has in some way
entered the system. Bleeding of brake system may be
performed by one of two methods — either pressure or
manual. Bleeder valves are provided at the calipers,
wheel cylinders and are also located on some master
cylinders.
Sequence for Bleeding Wheel Cylinders
It is advisable to bleed one valve at a time to avoid
allowing fluid level in reservoir to become dangerously
low. The correct sequence of bleeding is to bleed the
valve, either front or rear system, nearest master cylinder
first. This sequence expels air from lines and calipers or
wheel cylinders nearest the master cylinder first and
eliminates the possibility that air in a line close to the
master cylinder may enter a line farther away after it
has been bled.
CAUTIO N: Do not perform bleeding operation
while any brake drum is removed or with a
caliper removedfrom the disc.
Pressure Bleeding (Figs. 29 and 30)
NOTE: Pressure bleeding equipment must be
of the diaphragm type. That is, it must have
a rubber diaphragm between the air supply
and the brake fluid to prevent air, moisture,
oil and other contaminates from entering the
hydraulic system.
1. Clean all dirt from top of master cylinder and
remove cylinder cover and rubber diaphragm.
NOTE: Make sure brake fluid in bleeder
equipment is at operating level and that the
equipment is capable of exerting 20 to 30 lbs.
hydraulic pressure on the brake system.
2. Install Brake Bleeder Adapter J-23518 (J-23339 for
frame mounted boosters) on master cylinder.
Connect hose from bleeder equipment to bleeder
adapter and open release valve on bleeder
equipment.
NOTE: The combination valve, located near
the master cylinder, must be held in the open
position while bleeding. This can be accom&shy;
plished by installing Tool J-23709 with the
open slot under the mounting bolt and
pushing in on the pin in the end of the valve
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
Fig. 29-B rake Bleeder J-23518 and J-23709
G Model Shown
(fig. 29). Be sure to retorque the mounting
bolt after removing Tool J-23709.
Install Brake Bleeder Wrench J-21472 on caliper
bleeder valve nearest the master cylinder and install
one end of bleeder hose on bleeder valve.
NOTE: If the master cylinder is equipped
with bleeder valves, bleed these valves first,
proceed to the bleeder valve nearest the
master cylinder, then the next nearest and so
on until all valves have been bled and there
is no evidence of air in the system.
Pour a sufficient amount of brake fluid into a
transparent container to ensure that end of bleeder
hose will remain submerged during bleeding. Place
the loose end of bleeder hose into the container. Be
sure the hose end is submerged in the fluid.
Open bleeder valve by turning Tool J-21472
counterclockwise approximately 3/4 of a turn and
observe flow of fluid at end of bleeder hose.
NOTE: To assist the bleeding operation a
rawhide mallet may be used to tap the caliper
while fluid is flowing.
Close bleeder valve tight as soon as bubbles stop
and brake fluid flows in a solid stream from the
bleeder hose.
Remove brake bleeder wrench and bleeder hose
from bleeder valve.
Repeat Steps 3 through 7 on the remaining bleeder
valves.
Disconnect bleeder equipment from brake bleeder
adapter.
NOTE: The master cylinder on certain
models is tilted. When removing the bleeder
adapter on these models, place a clean dry
5-17
Fig. 3 0 -Bleeding Brakes with Tool J 21472
cloth below the cylinder to absorb any fluid
spillage as the cover is removed.
10. Remove bleeder adapter. Wipe all areas dry if fluid
was spilled during adapter removal.
11. Fill master cylinder reservoirs to within 1/4&quot; of
reservoir rims as shown in Figure 31.
12. Install master cylinder diaphragm and cover.
CAUTION: When installing the master cylinder
cover, the retaining bail should be slipped over
the lower cover bosses (fig. 32). Incorrect
installation could result in bail tension loss and
fluid leakage.
13. Test operation of brake pedal before moving the
vehicle.
Manual Bleeding
1. Clean all dirt from the top of the master cylinder
LIGHT DUTY TRUCK SERVICE MANUAL
5 -1 8 BRAKES
return slowly to the released position. Repeat Step 5
until expelled brake fluid flows in a solid stream
without the presence of air bubbles, then close the
bleeder valve tightly.
NOTE: To assist the bleeding operation a
rawhide mallet may be used to tap the caliper
while fluid is flowing.
6 . Remove brake bleeder wrench and hose from the
bleeder valve and repeat Steps 2 through 6 on the
remaining bleeder valves.
7. Fill the master cylinder to the level shown in Figure
31.
8 . Install the master cylinder diaphragm and cover.
CAUTION: When installing the master cylinder
and remove the cylinder cover and rubber
diaphragm.
2. Fill master cylinder (if necessary) and reinstall the
cover.
3. Install Brake Bleeder Wrench J-21472 on caliper
bleeder valve nearest the master cylinder and install
a bleeder hose on the bleeder valve (fig. 30).
NOTE: The combination valve, located near
the master cylinder, must be held in the open
position while bleeding. This can be accom&shy;
plished by installing Tool J-23709 with the
open slot under the mounting bolt and
pushing in on the pin in the end of the valve
(fig. 29). Be sure to retorque the mounting
bolt after removing Tool J-23709.
If the master cylinder is equipped with
bleeder valves, bleed these valves first, then
proceed to the bleeder valve nearest the
master cylinder, then the next nearest and so
on until all cylinders have been bled and
there is no evidence of air.
4. Pour a sufficient amount of brake fluid into a
transparent container to ensure that the end of the
bleeder hose will remain submerged during
bleeding. Place the loose end of the bleeder hose
into the container.
NOTE: Carefully monitor the fluid level at
the master cylinder during bleeding. Do not
bleed enough fluid at one time to drain the
reservoir. Replenish as needed to ensure a
sufficient amount of fluid is in the master
cylinder at all times.
5. Open bleeder valve by turning Tool J-21472
counterclockwise approximately 3/4 of a turn. Have
helper depress the brake pedal. Just before the
brake pedal reaches the end of its travel, close the
bleeder valve tightly and allow the brake pedal to
cover the retaining bail should be slipped over
the lower cover bosses (fig. 32). Incorrect
installation could result in bail tension loss and
fluid leakage.
NOTE: In order to have a good surge of fluid
at the bleeder valve, the brake pedal should
be pumped up and pressure held before each
opening of the valve.
HYDRAULIC BRAKE LINES AND TUBING
(Figs. 33 and 34)
Hydraulic Brake Hose
The flexible hoses which carry the hydraulic pressure
from the steel lines to the brake calipers are carefully
designed and constructed to withstand all conditions of
stress and twist which they encounter during normal
vehicle usage.
These hoses require no service other than periodic
inspection for damage from road hazards or other like
sources. Should damage occur and replacement become
necessary, the following procedure should be followed.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -1 9
BRAKE LINE
FUEL LINE
TO MASTER CYLINDER
FRONT BRAKE HOSE
REAR BRAKE HOSE
CO M BINATION
VALVE
AXLE
Fig. 34-Brake Line Retainers- Typical
Removal
1. Clean all dirt and foreign material away from both
hose fitting ends.
2. Separate steel line from flex hose. Use a back up
wrench on the hose fitting.
3. Remove clip retainer from frame attachment.
4. Remove hose to caliper bolt and remove hose.
Installation (Fig. 33)
1. Install the hose to the caliper using new gaskets.
Torque the mounting bolt.
CAUTION: See Caution on Page 1 of this
section.
Hose line must be installed in caliper locating
gate (except &quot;K&quot; models); connector arm in
caliper locating gate (&quot;K&quot; series).
2. Insert hose into frame bracket or frame. This end
of hose will properly mate to the bracket or frame
in one direction only.
3. Install the clip retainer.
4. Install the steel line to the flex line using a back up
wrench on the hose fitting.
CAUTION: See Caution on Page 1 of this
section.
5. Bleed brakes as outlined in this section.
Hydraulic Brake Tubing (Figs. 35 thru 39)
Hydraulic brake tubing used on all trucks is a double
wall steel tubing which resists corrosion and has the
physical strength to stand up under the pressures which
are developed when applying the brakes. In making up
hydraulic brake lines, it is important that the ends of the
tubing be flared properly for the compression couplings.;
CAUTION: When necessary to replace brake
tubing, always use double wall steel tubing
which is designed to withstand high pressure
and resist corrosion. Steel tubing must be
equivalent to G M Specification GM123M, be
annealed dead soft and super terne coated.
ORDINARY COPPER TUBING IS N O T
SATISFACTORY A N D S H O U L D N O T BE
USED.
When replacing brake lines, be sure to install
new spring steel shielding material over the
replacement line in the same areas as on the
line removed.
LIGHT DUTY TRUCK SERVICE MANUAl*
5 -2 0 BRAKES
Safety steel tubing must be double-lap flared at the ends
in order to produce a strong leak-proof joint.
Brake Tube Flaring Tool J-2185-45&deg; is used to form the
double lap flare. It must be equipped with the proper
size die block and upset flare punch for each size tubing
to form the double-lap flare (fig. 35).
The proper size die blocks and upset flare punches are as
follows:
Tubing Size
3/16”
1 /4 ”
5/16”
Die Block
J-2185-27
J-2185-28
J-2185-29
Upset
Flare Punch
J-2185-3
J-2185-37
J-2185-4
Finish
Flare Punch
J-2185-26
J-2185-26
J-2185-26
Figure 36 shows two pieces of tubing, one with single-lap
flare &quot;A&quot; and the other with double-lap flare &quot;B&quot;. It will
be noted that the single-lap flare in &quot;A&quot; split the tubing
while the one shown in &quot;B&quot; is well-formed and unbroken
due to the reinforcement of the double wall.
Fig. 35-Flaring Tool J-2185
The following procedure should be followed in making
up hydraulic brake lines.
Double Lap Flaring
1. Cut the tubing to the desired length, using Tool
J-8000. Square off ends of tube and ream sharp
edges with reamer tool provided on the tube cutter.
2. Install compression couplings on tubing and dip
end of tubing to be flared in hydraulic brake fluid.
This lubrication results in better formation of the
flare.
3. Place one-half of the die blocks in the tool body
with the counterbored ends toward the ram guide.
Now lay the tubing in the block with approximately
1/4&quot; protruding beyond the end.
Fit the other half of the block into the tool body,
close the latch plate and tighten the nuts &quot;finger
tight.&quot;
4. Select the correct size upset flare punch. One end of
this punch is hollowed out to gauge the amount of
tubing necessary to form a double-lap flare.
5. Slip the punch into the tool body with the gauge
end toward the die blocks, install the ram and tap
lightly until the punch meets the die blocks and
they are forced securely against the stop plate (fig.
37).
6 . Using the supplied wrench, draw the latch plate nut
down tight to prevent the tube from slipping.
Tightening the nuts alternately (beginning with the
nut at the closed hole in the plate), will prevent
distortion of the plate. Remove the punch and the
ram. Now reverse the punch and put it back into
the tool body. Install the ram and tap it until the
upset flare is complete (fig. 38). This completes the
first operation. Remove the ram and the punch.
7. To complete the flare, insert the pointed finish flare
punch and the ram into the tool body. Tap the ram
until a good seat is formed (fig. 39).
NOTE: The seat should be inspected at
intervals during the finishing operation to
avoid over-seating.
8 . Blow tubing out with compressed air to remove any
foreign objects.
LATCH PLATEDIE BLOCK
TUBE
UPSET FLARE PUNCH
RAM GUIDE
RAM
STOP PLATE
Fig. 3 6 -Single and Double Lap Flare
Fig. 3 7 -Positioning Tube
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
LATCH PLATE
DIE BLOCK\
TUBE
T
UPSET FLARE PUNCH
5-21
RAM GUIDE
r RAM
PLATE
Fig. 38--Flaring O peration
DRUM BRAKE ADJUSTMENT
Service Brake
Although the brakes are self adjusting a preliminary or
initial adjustment may be necessary after the brakes
have been relined or replaced, or whenever the length of
the adjusting screw has been changed. The final
adjustment is make by using the self adjusting feature.
1. With brake drum off, disengage the actuator from
the star wheel and rotate the star wheel.
Recommended Method of Adjustment (Fig. 40)
Fig. 40--Using D rum -to-B rake Gauge J-21177
a. Use Drum to Brake Shoe Clearance Gauge
J-21177 to check the diameter of the drum
clearance surface (fig. 40).
b. Turn the tool to the opposite side and fit over
the brake shoes by turning the star wheel until
the gauge just slides over the linings (fig. 41).
c. Rotate the gauge around the brake shoe lining
surface to assure proper clearance.
Alternate Method of Adjustment
a. Using the brake drum as an adjustment fixture,
turn the star wheel until the drum slides over the
brake shoes with a slight drag.
Fig. 41--Setting Lining Clearance w ith J-21177
b. Turn the star wheel 1-1/4 turns to retract the
shoes. This will allow sufficient lining to drum
clearance so final adjustment may be made as
described in Step 3.
2. Install the drum and wheel and remove the vehicle
from the jack stands or hoist.
CAUTIO N: If lanced area in drum or flange
plate was knocked out, be sure all metal has
been removedfrom brake compartment. Install
a new metal hole cover to prevent contamina&shy;
tion of the brakes.
Make certain when installing drums that drums
are installed in the same position as when
LIGHT DUTY TRUCK SERVICE MANUAL
5 -2 2 BRAKES
removed, with the drun locating tang in line
with the locating hole in he axle shaftflange.
3. Make final adjustmei by making numerous
forward and reverse stc 3S, applying brakes with a
firm pedal effort until a satisfactory brake pedal
height results.
CAUTION: Frequent u age of an automatic
transmission forward mge to halt reverse
vehicle motion may P event the automatic
adjusters from functior mg, thereby inducing
low pedal heights.
push rod. Power brake units incorporate a two-piece
push rod. Ordinarily there would be no reason to change
the push rod dimension; however, if the rod were
inadvertently lengthened or shortened, the correct
dimension is given in Figure 42.
NOTE: To adjust, it would be necessary to
remove the unit from the vehicle, loosen the
locknut and adjust to the dimension shown,
retighten the locknut and reinstall the unit.
STOPLAMP SWITCH ADJUSTMENT (Fig. 43)
BRAKE PEDAL FREE 1 RAVEL ADJUSTMENT
G-P Models
A definite pedal push rod to-master cylinder piston
clearance must be maintaine 1 on G and P model dash
mounted master cylinder ui its (manual brakes). This
clearance is adjusted as follov s:
1. After the brake pedal ai d pedal bumper have been
assembled, install the f ush rod and its attaching
parts. Then to obtain th correct clearance between
the push rod and the i aster cylinder, adjust the
push rod so that the
pedal travel measured at
the center of the pedal pad is .06-.25 inches (fig.
42).
2. After tightening the loci nut on the adjustable push
rod, recheck free travel.
CAUTION: See &quot;Cautio i&quot; on Page 1 of this
section.
C-K Models
Manual brake vehicles do no incorporate an adjustable
The stoplamp switch is mounted on a flange protruding
from the brake pedal support.
Adjustment
1. Release the brake pedal to its normal position.
2 . Adjust the switch by rotating the switch in its
bracket. Electrical contact should be made when the
pedal travel (measured at the center of the pedal
pad) is 3/8-5/8&quot; (C-K models), approximately 5/8&quot;
(P-G models).
3. Tighten switch locknut, if so equipped, and connect
electrical harness.
BRAKE TRAVEL WARNING SWITCH
ADJUSTMENT
Refer to &quot;Brake Travel Warning Switch&quot; under
Component Replacement in this section.
PARKING BRAKE-REAR WHEEL
The rear brake assemblies (except RPO H22—where
Fig. 42- Brake Pedal Adjustment-Typical
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
parking brake is mounted on the propeller shaft) serve a
dual purpose in that they are utilized both as a
hydraulically operated service brake and also as a
mechanically operated parking brake. In view of this
dual purpose, the service brake must be properly
adjusted as a base for parking brake adjustment;
conversely the parking brake must be properly adjusted
for the service brake to function as intended.
Inspection
If complete release of the parking brake is not obtained,
unless it is forcibly returned to its released position, or if
application effort is high, check parking brake assembly
for free operation. If operation is sticky or a bind is
experienced, correct as follows:
1. Clean and lubricate brake cables and equalizer with
Delco Brake Lube #5450032 (or equivalent).
2. Inspect brake assembly for straightness and
alignment (replace if necessary).
3. Clean and lubricate parking brake assembly with
Delco Brake Lube #5450032 (or equivalent).
4. Checking routing of cables for kinks or binding.
Adjustment—Foot Pedal Type
1.
2.
3.
4.
NOTE: Before adjusting parking brake,
check service brake condition and
adjustment.
Raise vehicle on hoist.
Apply parking brake 1 notch from fully released
position.
Loosen equalizer check nut and tighten the
adjusting nut until a moderate drag is felt when the
rear wheels are rotated forward.
Tighten the check nut to specifications.
CAU TIO N : See Caution on Page 1 of this
section.
5. Fully release parking brake and rotate the rear
wheels. No drag should be present.
6 . Remove vehicle from hoist.
Adjustment—Orscheln Lever Type
1. Turn adjusting knob on parking brake lever
counterclockwise to stop.
2. Apply parking brake.
3. Raise vehicle on a hoist.
4. Loosen lock nut at intermediate cable equalizer and
adjust front nut to give light drag at rear wheels.
Tighten the check nut to specifications.
CAUTIO N: See Caution on Page 1 of this
section.
5. Readjust parking brake lever knob to give a definite
snap-over-center feel.
5 -2 3
6 . Fully release parking brake and rotate rear wheels.
No drag should be present.
7. Remove vehicle from hoist.
PARKING BRAKE (PROPELLER S H AFT)INTERNAL EXPANDING
Adjustment—Drum On
1. Jack up at least one rear wheel. Block wheels and
release hand brake.
2. Remove cotter pin and clevis pin connecting pull
rod and relay lever. This will assure freedom for
full shoe release.
CAUTIO N: It may be necessary to knock out
lanced area in brake drum with punch and
hammer to gain entry into adjusting screw
through brake drum. Be sure all metal has been
removedfrom parking brake compartment.
3. Rotate brake drum to bring one of access holes into
line with adjusting screw at bottom of shoes.
4. Expand shoes by rotating adjusting screws with
screwdriver inserted through hole in drum. Move
outer end of screwdriver away from drive shaft.
Continue adjustment until shoes are tight against
drum and drum cannot be rotated by hand. Back
off adjustment ten notches and check drum for free
rotation.
5. Place parking brake lever in fully released position.
Take up slack in brake linkage by pulling back on
cable just enough to overcome spring tension.
Adjust clevis of pull rod or front cable to line up
with hole in relay levers.
a. Insert clevis pin and cotter pin, then tighten
clevis locknut.
b. Install a new metal hole cover in drum to
prevent contamination of brake.
c. Lower rear wheels. Remove jack and wheel
blocks.
CAUTIO N: See &quot;Caution&quot; on Page 1 of this
section.
Adjustment—Drum Off
1. With parking brake drum off, use special Tool
J-21177 or J-22364, Drum to Brake Shoe Clearance
Gauge, to check diameter of drum clearance
surface.
2. Turn the tool to the opposite side and fit over brake
shoes by turning the star wheel until the gauge just
slides over the linings.
3. Rotate the gauge around the brake shoe lining
surface to insure proper clearance.
4. Install propeller shaft flange at mainshaft as
outlined in transmission section.
5. Lower rear wheels. Remove jack and wheel blocks.
LIGHT DUTY TRUCK SERVICE MANUAL
5 - 2 4 BRAKES
C O M P O N E N T REPLACEMENT A N D REPAIRS
SHOES AND LININGS—REAR DRUM
BRAKES (Fig. 44)
NOTE: If brake drums are worn severely, it
may be necessary to retract the adjusting
screw. To gain access to the adjusting screw
star wheel, knock out the lanced area in the
brake drum or flange plate using a chisel or
similar tool. Release the actuator from the
star wheel with a small screwdriver on models
with access hole in flange plate or with a wire
hook on models with hole in drum. Back off
the star wheel with a second screwdriver (as
shown in Figures 45 and 46).
CAUTIO N: After knocking out the metal, be
sure to remove it from the inside of the drum
and clean all metal from the brake compart&shy;
ment. A new metal hole cover must be
1. Raise the vehicle on hoist.
2. Loosen check nuts at forward end of parking brake
equalizer sufficiently to remove all tension from
brake cable.
3. Remove brake drums.
CAUTION: The brake pedal must not be
depressed while drums are removed.
4. Unhook brake shoe pull back springs from anchor
pin and link end, using tool J-8049 (fig. 47).
5. Remove the actuator return spring.
6 . Disengage the link end from the anchor pin and
then from the secondary shoe.
7. Remove hold-down pins and springs using any
suitable tool (fig. 48).
installed when drum is reinstalled.
Drum brake lining can be inspected through slots in the
flange plate. The portion of lining visible through the
slot will not necessarily be the area of maximum wear
and extra caution is necessary to make sure lining is
replaced prior to the point where the remaining
thickness, as viewed through the inspection slot, is as
follows:
Series 10 (bonded lining), 1/16&quot;
Series 20, 30 (riveted lining), 3/16&quot;
NOTE: Riveted linings should be replaced
when worn within 1/32&quot; of rivet heads.
Removal
NOTE: See Section 4 (Rear Suspension and
Driveline) for non-demountable type hub
and drum removal.
PULL BACK SPRINGS
Fig. 45--Flange Plate Access Hole
PRIMARY SHOE
Fig. 4 4 -Rear Brakes
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -2 5
2. Carefully pull lower edges of wheel cylinder boots
away from cylinders and note whether interior is
wet with brake fluid. Excessive fluid at this point
indicates leakage past piston cups requiring
overhaul of wheel cylinder.
NOTE: A slight amount of fluid is nearly
always present and acts as lubricant for the
piston.
3. Inspect flange plate for oil leakage past axle shaft
oil seals. Install new seals if necessary.
4. Check all brake flange plate attaching bolts to make
sure they are tight. Clean all rust and dirt from
shoe contact faces on flange plate (fig. 49), using
fine emery cloth.
Fig. 47-Unhooking Pull Back Spring
8 . Remove the actuator assembly.
NOTE: The actuator, pivot and override
spring are an assembly. It is not recom&shy;
mended that they be disassembled for service
purposes, unless they are broken. It is much
easier to assemble and disassemble the
brakes by leaving them intact.
9. Separate the brake shoes by removing adjusting
screw and spring.
CAUTIO N: Mark shoe and lining positions if
they are to be reinstalled.
10. Remove parking brake lever from secondary brake
shoe.
Installation
CAUTIO N: Make certain to install recom&shy;
mended shoe and lining assemblies.
1. Inspect new linings and make certain there are no
nicks or burrs or bonding material on shoe edge
where contact is made with brake flange plate or on
any of the contact surfaces.
CAUTIO N: Keep hands clean while handling
brake shoes. Do not permit oil or grease to
come in contact with linings.
2. Lubricate parking brake cable with Delco Brake
Lube #5450032 (or equivalent).
3. Lubricate fulcrum end of parking brake lever and
the bolt with Delco Brake Lube #5450032 (or
equivalent), then attach lever to secondary shoe
with bolt, spring washer, lock washer and nut. Make
sure that lever moves freely.
Inspection
1. Clean dirt out of brake drum. Inspect drums for
roughness, scoring or out-of-round. Replace or
recondition drums as necessary.
Fig. 48-Removing Hold Down Spring and Pin
Fig. 49- Flange Plate Contact Surfaces
LIGHT DUTY TRUCK SERVICE MANUAL
5 -2 6 BRAKES
4. Before installation, make certain the adjusting
screw is clean and lubricated properly.
CAUTION: Loose adjustment may occur from
an adjusting screw that is not properly
operating. If the lubrication in the adjusting
screw assembly is contaminated or destroyed,
the adjusting screw should be thoroughly
cleaned and lubricated with Delco Brake Lube
#5450032 (or equivalent).
5. Connect brake shoes together with adjusting screw
spring, then place adjusting screw, socket and nut in
position.
CAUTION: Make sure the proper adjusting
screw is used (left hand or right hand). The
star wheel should only be installed with the star
wheel nearest to the secondary shoe and the
adjusting screw spring inserted to prevent
interference with the star wheel. Make sure
right hand thread adjusting screw is on leftside
of car and left hand thread adjusting screw is
on right side of car. Make certain star wheel
lines up with adjusting hole inflange plate.
anchor pin stud with the regular spring hook
tool. Fasten the wire link to the actuator
assembly first, and then place over the anchor
pin stud by hand while holding the adjuster
assembly infull down position.
11. Install actuator return spring.
CAUTION: Do not pry actuator lever to install
return spring. Ease it in place using the end of
a screwdriver or other suitableflat tool.
12. If old brake pull back (return) springs are nicked,
distorted, or if strength is doubtful, install new
springs.
13. Hook springs in shoes using Tool J-8049 by
installing the primary spring from the shoe over the
anchor pin and then the spring from the secondary
shoe over the wire link end (fig. 50).
14. Pry shoes away from the flange plate and lubricate
shoe contact surfaces with a thin coating of Delco
Brake Lube #5450032 (or equivalent).
CAUTION: Be careful to keep lubricant off
facings.
If original shoe and lining assemblies are being
reinstalled, they must be installed in original
positions (as marked at removal).
6 . Install parking brake cable.
7. Secure the primary brake shoe (short lining faces
forward) first with the hold down pin and spring
using a pair of needle nose pliers. Engage shoes
with the wheel cylinder connecting links.
8 . Install and secure the actuator assembly and
secondary brake shoe with the hold down pin and
spring using a pair of needle nose pliers. Position
parking brake strut and strut spring.
9. Install guide plate over anchor pin.
10. Install the wire link.
CAUTION: Do not hook the wire link over the
15. After completing installation, make certain the
actuator lever functions easily by hand operating
the self-adjusting feature (fig. 51).
16. Follow the above procedure for all brakes.
17. Adjust the service brakes and parking brake as
outlined under &quot;Maintenance and Adjustments&quot; in
this section.
18. Install drum, wheel and tire and lower the vehicle to
floor. Test brake operation.
Relining Brake Shoes
If old brake shoes are to be relined, inspect shoes for
distortion and for looseness between the rim and web;
these are causes for discarding any shoe. If shoes are
serviceable, be governed by the following points in
installing new linings:
1. Remove old linings by drilling out rivets. Punching
rivets out will distort shoe rim. Thoroughly clean
FWD
Fig. 5 0 -Installing Pull Back Spring
Fig. 5 1 -Checking Actuating Lever
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
surface of shoe rim and file off any burrs or high
spots.
2. Use released brake lining (or equivalent) and the
rivets included in lining package which are of the
correct size. The rivets must fit the holes with the
solid body of rivet extending through the shoe rim,
but no farther.
CAUTION: Keep hands clean while handling
brake lining. Do not permit oil or grease to
come in contact with lining.
3. Start riveting at center of shoe and lining and work
toward the ends. Use a roll set for reveting; a star
set might split the tubular end and then the rivet
would not fill the hole. The primary lining is shorter
than secondary lining, therefore, the rivet holes at
each end of the shoe rim are not used.
4. After riveting is completed, lining must seat snugly
against shoe with no more than .005&quot; separation
midway between rivets. Check with a .004&quot; (Go)
and a .006 (No Go) feeler gauge.
ANCHOR PIN REPLACEMENT
Removal
1. Raise vehicle on a hoist.
2. Remove wheel and drum as outlined in this section.
3. Remove brake shoe pull back springs, link and
guide plate.
4. Disengage anchor pin lock and remove pin from
flange plate (Threaded type).
Installation
1. Position anchor pin to flange plate, install lock
washer and torque pin. Lock by peening over
washer tabs.
CAUTION:
See Caution on Page 1 of this
section.
2. Install brake shoe guide plate, link and pull back
springs.
3. Adjust brakes, install drum and wheel as outlined
previously in this section.
4. Lower vehicle and test brake operation.
WHEEL CYLINDER
CAUTION: Always use clean brake fluid to
clean wheel cylinder parts. Never use mineralbase cleaning solvents such as gasoline,
kerosene, carbon-tetrachloride, acetone, paint
thinner or units of like nature as these solvents
deteriorate rubber parts, causing them to
become soft and swollen in an extremely short
time.
The wheel cylinder boots should be removed from a
cylinder body only when they are visibly damaged or
5-27
leaking fluid. Wheel cylinders having torn, cut, or heatcracked boots should be completely overhauled.
Wheel Cylinder Repair
Wheel cylinders should not be disassembled unless they
are leaking or unless new cups and boots are to be
installed. It is not necessary to remove the wheel cylinder
from the flange plate to disassemble, inspect, and
overhaul the cylinder. Removal is necessary only when
the cylinder is damaged or scored beyond repair.
Removal
1. Place vehicle on hoist.
2. Remove wheel and tire assembly. Back off brake
adjustment, if necessary, and remove drum.
3. Disconnect brake system hydraulic line from
cylinder.
4. Remove brake shoe pull back springs.
5. Remove screws securing wheel cylinder to flange
plate. Disengage cylinder push rods from brake
shoes and remove cylinder.
Disassembly (Fig. 52)
1. Remove boots from cylinder ends.
2. Remove pistons and cups.
Inspection and Cleaning
NOTE: Staining is not to be confused with
corrosion. Corrosion can be identified with
pits or excessive bore roughness.
1. Inspect cylinder bore. Check for staining and
corrosion. Discard cylinder if corroded.
2. Polish any discolored or stained area with crocus
cloth by revolving the cylinder on the cloth
supported by a finger. Do not slide the cloth in a
lengthwise manner under pressure.
CAUTION: Before washing parts, hands must
be clean. Do not wash hands in gasoline or oil
before cleaning parts. Use soap and water to
clean hands.
3. Wash the cylinder and metal parts in clean brake
fluid.
4. Remove excess cleaning fluid from the cylinder. Do
not use a rag to dry the cylinder as lint from the
rag cannot be kept from the cylinder bore surfaces.
5. Check piston for scratches or other visual damage;
replace if necessary.
Assembly (Fig. 52)
1. Lubricate the cylinder bore with clean brake fluid
and insert spring-expander assembly.
2. Install new cups with flat surface toward outer ends
of cylinder. Be sure cups are lint and dirt free
before insertion. Do not lubricate cups prior to
assembly.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -2 8 BRAKES
WARNING: A cracked drum is unsafe for
further service and must be replaced. Do not
attempt to weld a cracked drum.
PUSH ROD AN D BOOT
PISTON
CUP RETURN SPRING WITH EXPANDERS
WHEEL CYLINDER HOUSING
PISTON CUP
PISTON CUP
BLEEDER SCREW
PUSH ROD AN D BOOT
Fig. 52 -Wheel Cylinder-Explode
3. Install new pistons into cylinder with flat surfaces
toward center of cylinder. Do not lubricate pistons
before installation.
4. Press new boots onto cylinder by hand. Do not
lubricate boots prior to installation.
Installation
1. Position wheel cylinder to brake flange plate. Install
screws and tighten securely.
CAUTION:
See Caution on Page 1 of this
section.
2. Install all push rods and pull back springs.
3. Connect hose or line to wheel cylinder.
CAUTION:
See Caution on Page 1 of this
section.
Install drum, wheel and tire assembly.
5. Bleed system as outlined in this section.
6 . Remove vehicle from hoist.
4.
BRAKE DRUMS
A lanced &quot;knock out&quot; area is provided in the brake
flange plate or brake drum for servicing purposes in the
event retracting of the brake shoes is required in order
to remove the drum.
A small screwdriver or hooked wire may be inserted to
disengage the automatic adjuster actuating lever so the
star wheel may be turned.
Inspecting and Reconditioning
Whenever brake drums are removed, they should be
thoroughly cleaned and inspected for cracks, scores, deep
grooves and out-of-round. Any of these conditions must
be corrected since they can impair the efficiency of brake
operation and cause premature failure of other parts.
Smooth up any slight scores by polishing with fine emery
cloth. Heavy or extensive scoring will cause excessive
brake lining wear, and it will probably be necessary to
refinish in order to true up the braking surface.
If the brake linings are slightly worn and the drum is
grooved, the drum should be turned just enough to
remove grooves. The ridges in the lining should be
lightly removed with a lining grinder.
If brake linings are more than half worn but do not need
replacement, the drum should be polished with fine
emery colth but should not be turned. At this stage,
eliminating all grooves in drum and smoothing the
ridges on lining would necessitate removal of too much
metal and lining, while if let alone, the grooves and
ridges match and satisfactory service can be obtained.
If drum is to be refinished for use with standard size
brake facings which are worn very little, only enough
metal should be removed to obtain a true smooth
braking surface.
A brake drum must not be refinished more than .060&quot;
over the maximum standard diameter.
Out-Of-Round Or Tapered Drum
A drum that is more than .006 out-of-round on the
diameter will result in rough brake application and
should be refinished. Out-of-round and the diameter can
only be accurately measured with an inside micrometer
fitted with proper extension rods.
An out-of-round drum makes accurate brake shoe
adjustment impossible and is likely to cause excessive
wear of other parts of brake mechanism due to its
eccentric action. An out-of-round drum can also cause
severe and irregular tire tread wear as well as a pulsating
brake pedal. When the braking surface of a brake drum
exceeds the factory specification limits in taper and/or
being out-of-round, the drum should be turned to true
up the braking surface. Out-of-round as well as taper
and wear can be accurately measured with an inside
micrometer fitted with proper extension rods.
When measuring a drum for out-of-round, taper and
wear, take measurements at the open and closed edges of
machined surface and at right angles to each other.
Micrometer Method (Fig 53)
1. Place the brake drum on a smooth surface.
2. Using micrometers, place the tips at the center of
the drum face.
3. While sweeping horizontally and vertically, slowly
adjust the micrometer until maximum contact is
made. Record this reading.
4. Rotate the drum 45 degrees and repeat Step 3.
Continue until 4 readings have been made. The
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
difference between these 4 readings must not exceed
.006.
Cleaning
New brake drums are given a light coating of rust
proofing oil to prevent the formation of rust on the
critical braking surfaces during the time that the drums
are in storage.
This rust proofing oil must be carefully removed before
the drum is placed in service to prevent any of this oil
from getting on the brake shoe facings.
It is recommended that a suitable volatile, non-toxic,
greaseless type solvent be used to clean the oil from the
braking surface of the new brake drums before they are
placed in service to insure the cleanest possible surface.
Gasoline or kerosene should not be used as there is
danger that a portion of the diluted oil substance may be
left on the braking surface.
NOTE: All brake drums have a maximum
diameter cast into them. This diameter is the
maximum wear diameter and not a refinish
diameter. Do not refinish a brake drum that
will not meet the specifications as shown
below after refinishing.
ORIGINAL
DIAMETER
11.000
12.000
13.000
MAXIMUM REFINISH
DIAMETER
11.060
12.060
13.060
REPLACEMENT
(DISCARD)
DIAMETER
11.090
12.090
13.090
SHOE AND LININGS—FRONT DISC BRAKE
The brake linings should be inspected any time that the
5 -2 9
wheels are removed. Check both ends of the outboard
shoe by looking in at each end of the caliper. This is the
point at which the highest rate of wear normally occurs.
At the same time, check the lining thickness on the
inboard shoe by looking down through the inspection
hole in the top of the caliper--See &quot;Brake Inspection&quot;.
The outboard shoes have ears near the outer edge which
are bent over at right angles to the shoe. The top ends of
the shoe have looped ears with holes in them which the
caliper retaining bolts fit through. The large tab at the
bottom of the shoe is bent over at a right angle and fits
in the cut-out in the outboard section of the caliper.
The inboard shoe and lining has ears on the top ends
which fit over the caliper retaining bolts. A special spring
inside the hollow piston supports the bottom edge of the
inboard shoe.
NOTE: Outboard shoes (with formed ears)
are designed for original installation only
and are fitted to the caliper. The shoes should
never be relined or reconditioned for
reinstallation.
Removal
1. Remove master cylinder cover and observe brake
fluid level in front reservoir. If reservoir is more
than 1/3 full, siphon the necessary amount out to
bring the level to 1/3 full; this step is taken to
avoid reservoir overflow when the caliper piston is
pushed back into its bore.) Discard the brake fluid
removed. Never reuse brake fluid.
i
2. Raise the vehicle and remove the front wheels.
3. Push the piston back into its bore. This can be
accomplished by using a &quot;C&quot; clamp as shown in
Figure 54,
4. Remove the two mounting bolts which attach the
caliper to the support (fig. 55).
5. Lift the caliper off the disc.
6 . Remove the inboard shoe. Dislodge the outboard
shoe and position the caliper on the front
suspension arm so that the brake hose will not
support the weight of the caliper.
CAUTION: Mark shoe positions if they are to
be reinstalled.
7. Remove the shoe support spring from the piston.
8 . Remove the two sleeves from the inboard ears of
the caliper.
9. Remove the four rubber bushings from the grooves
in each of the caliper ears.
Cleaning and Inspection
Fig. 53-Measuring Drum Diameter
NOTE: The shoes should be replaced when
the lining is worn to approximately 1/32&quot;
over the rivet heads. Replace shoes in axle
sets.
1. Thoroughly clean the holes and the bushing grooves
LIGHT DUTY TRUCK SERVICE MANUAL
5 -3 0 BRAKES
Installation
CAUTION: If original shoes are being
reinstalled, they must be installed in original
positions (as marked at removal).
1. Lubricate new sleeves, new rubber bushings, the
bushing grooves and the end of the mounting bolts
using Delco Silicone Lube #5459912 or equivalent
(fig. 56).
CAUTION: It is essential that new sleeves and
rubber bushings be used and that lubrication
instructions be followed in order to ensure the
properfunctioning of the sliding caliper design.
Fig. 54-&quot;C &quot; Clamp for Removal Aid
in the caliper ears and wipe any dirt from the
mounting bolts.
CAUTION: Do not use abrasives on the bolts
since this may damage the plating. If the bolts
are damaged or corroded, they should be
replaced.
2. Examine the inside of the caliper for evidence of
fluid leakage. If leakage is noted, the caliper should
be overhauled.
3. Wipe the inside of the caliper clean, including the
exterior of the dust boot. Check the boot for cuts,
cracks or other damage.
CAUTION: Do not use compressed air to clean
the inside of the caliper. This may cause the
dust boot to become unseated.
2. Install the new rubber bushings in the caliper ears.
3. Install the new sleeves to the inboard ears of the
caliper.
NOTE: Position the sleeve so that the end
toward the shoe and lining assembly is flush
with the machined surface of the ear.
4. Install the}shoe support spring and the &quot;inboard&quot;
shoe in the center of the piston cavity as shown in
Figure 57.
5. Push down until the shoe lays flat against the
caliper (fig. 58).
6 . Position the outboard shoe in the caliper with the
ears at the top of the shoe over the caliper ears and
the tab at the bottom of the shoe engaged in the
caliper cutout.
7. With both shoes installed, lift up the caliper and
rest the bottom edge of the outboard lining on the
outer edge of the brake disc to make sure there is
Fig. 5 6 -Lubrication Points
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
no clearance between the tab at the bottom of the
outboard shoe and the caliper abutment.
8 . Position the caliper over the brake disc, lining up
the hole in the caliper ears with the holes in the
mounting bracket.
NOTE: Make sure that the brake hose is not
twisted or kinked.
9. Start the caliper to mounting bracket bolts through
the sleeves in the inboard caliper ears and through
the mounting bracket, making sure that the ends of
the bolts pass under the retaining ears on the
inboard shoe.
10. Push the mounting bolts through to engage the
holes in the outboard shoes and the outboard
caliper ears, threading the mounting bolts into the
mounting bracket.
5-31
11. Torque the mounting bolts to 35 ft. lbs.
CAUTION: See &quot;Caution&quot; on Page 1 of this
section.
12. Pump the brake pedal to seat the linings against the
rotors.
13. Using arc joint pliers, as shown in Figure 59, bend
both upper ears of the outboard shoe until no
radial clearance exists between the shoe and the
caliper housing. Locate pliers on small notch of
caliper housing during clinching procedure.
CAUTION: If radial clearance exists after
initial clinching, repeat Step 13.
NOTE: Outboard shoes (with formed ears)
are designed for original installation only
and are fitted to the caliper. The shoes should
never be relined or re-conditioned for
reinstallation.
14. Reinstall the front wheel and lower the vehicle.
15. Add brake fluid to the master cylinder reservoir to
bring the fluid level up to within 1/4 inch of the
top.
NOTE: Before moving the vehicle, pump the
brake pedal several times to make sure that it
is firm. Do not move vehicle until a firm
pedal is obtained. Check master cylinder
fluid level again after pumping the brake
pedal.
CALIPER OVERHAUL
CAUTION: Always use clean brake fluid to
clean any caliperparts. Never use mineral-base
cleaning solvents such as gasoline, kerosene,
carbon-tetrachloride, acetone, paint thinner or
units of like nature as these solvents deteriorate
rubber parts, causing them to become soft and
swollen in an extremely short time.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -3 2 BRAKES
Fig. 60--Caliper Explode
Removal
CAUTION:
Clean dirt from hose to caliper
connection beforeproceeding with removal.
1. Remove master cylinder cover and observe brake
fluid level in front reservoir. If reservoir is more
than 1/3 full, siphon the necessary amount out to
bring the level to 1/3 full. This step is taken to
avoid reservoir overflow when the caliper piston is
pushed back into its bore. Discard the brake fluid
removed. Never reuse brake fluid.
2. Raise the vehicle and remove the front wheels.
3. Push the piston back into its bore. This can be
accomplished by using a &quot;C&quot; clamp as shown in
Figure 54.
4. Remove the hose to caliper bolt and cap or tape the
open connections to prevent dirt from entering the
hose or caliper. Discard the copper gaskets.
5. Remove the caliper assembly and then remove the
brake shoes from the caliper.
CAUTION: Mark discpad locations ifpads are
to be reinstalled.
Disassembly
1. Clean the exterior of the caliper using clean brake
fluid and place on a clean work surface.
2. Drain the brake fluid from the caliper.
WARNING: Do not place the fingers in front
of the piston in an attempt to catch or protect
it when applying compressed air.
3. Using clean shop towels, pad the interior of the
caliper and remove the piston by directing
compressed air into the caliper inlet hole (fig. 61).
CAUTION: Usejust enough airpressure to ease
the piston out of the bore. Do not blow piston
out of the bore.
NOTE: An alternate method of removing the
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -3 3
primary sealing surface in the caliper assembly.
It is manufactured and plated to close
tolerances. Refinishing by any means or the use
of any abrasive is not an acceptable practice.
BRAKE FLUID
INLET HOLE
4. Check the bore in the caliper for the same defects
as the piston. The piston bore, however, is not
plated and stains or minor corrosion can be
polished with crocus cloth.
AIR HOSE
SHOP
TOWELS
CAUTIO N: Do not use emery cloth or any other
form of abrasive. Thoroughly clean the caliper
after the use of crocus cloth. If the bore cannot
be cleaned up in this manner, replace the
caliper.
Assembly
Fig. 61 -Removing Piston From Caliper
piston is to stroke the brake pedal (gently)
while the hydraulic lines are still connected.
This will push the piston out of the caliper
bore.
4. Using a screwdriver and caution so as not to scratch
the piston bore, pry the dust boot out of the caliper
piston bore.
5. Using a small piece of wood or plastic, remove the
piston seal from its groove in the caliper piston
bore.
CAUTIO N: Do not use a metal tool of any kind
for this operation as itmay damage the bore.
6 . Remove the bleeder valve from the caliper.
7. Remove and discard the sleeves and bushings from
the caliper ears.
Cleaning and Inspection
CAU TIO N: The dust boot, piston seal, rubber
bushings and sleeves are to be replaced each
time that the caliper is overhauled. Discard
these parts - do not bother to clean and inspect
them.
1. Lubricate the caliper piston bore and the new
piston seal with clean brake fluid. Position the seal
in the caliper bore groove.
2. Lubricate the piston with clean brake fluid and
assemble a new boot into the groove in the piston
so that the fold faces the open end of the piston as
shown in Figure 62.
3. Insert the piston into the caliper bore using care not
to unseat the seal and force (50 to 100 pounds force
required) the piston to the bottom of the bore.
4. Position the dust boot in the caliper counterbore
and seat using Boot Installer Tool J-22904 as shown
in Figure 63.
CAUTIO N: Check the boot installation to make
sure that the retaining ring moulded into the
boot is not bent and that the boot is installed
below the caliperface and evenly all around.
5. Install the bleeder screw and
specifications.
1. Clean all parts (other than those mentioned above)
in clean brake fluid. Use dry, filtered, compressed
air to blow out all passages in the caliper and
bleeder valve.
torque
to
DU ST B O O T
CAUTIO N: The use of lubricated shop air will
leave a film of mineral oil on the metal parts.
This may damage rubberparts when they come
in contact after reassembly.
2. Check the mounting bolts for corrosion or other
damage. Do not attempt to clean up the bolts. If
they appear corroded - replace them.
3. Carefully examine the outside surface of the piston
for scoring, nicks, corrosion and worn or damaged
chrome plating. If any surface defects are detected,
replace the piston.
PISTON
END OF GROOVE
Fig. 6 2 -Installing Boot to Piston
CAUTION: The piston outside diameter is the
LIGHT DUTY TRUCK SERVICE MANUAL
5 -3 4 BRAKES
Installation
NOTE: Installation of the caliper and
mounting parts (rubber bushings, sleeves,
bolts, and shoe and lining assemblies) is the
same as for: Brake Shoes and Linings except for the steps given below.
1. Connect the brake hose to the caliper using new
copper gaskets. Torque connector bolt to
specifications.
CAUTIO N: Hose must be positioned in the
caliper locating gate (between locating beads)
to assure proper positioning to caliper.
variation, flatness and parallelism are out of specifica&shy;
tion. Scoring of the brake disc surfaces not exceeding
.015 inch in depth, which may result from normal use,
is not detrimental to brake operation.
CAUTION: Both sides of the disc must be
treated in the same manner. If one side needs
resurfacing or reconditioning the opposite side
should be treated in the same manner.
REPLA C E if the disc cannot be reconditioned to bring it
within specifications and meet the minimum thickness
specification after reconditioning.
CAUTION: All brake disc have a minimum
thickness dimension cast into them. This
dimension is the minimum wear dimension and
not a refinish dimension. Do not refinish a
brake disc that will not meet the specifications
as shown below after refinishing:
See &quot;Caution&quot; on page Iof this section.
2.
Bleed the calipers using the method outlined earlier
in this section.
DISC SERVICING
Servicing of the brake disc is extremely critical since
accurate control of the disc tolerances is necessary to
ensure proper brake operation.
Brake discs can be refinished if precision equipment is
available and a few simple rules are followed. The first
thing to do is to determine which of the following will
need to be done. RESURFACE, RECONDITION or
REPLACE.
R ESU R FA CE with a flat sanding disc (with disc
rotating) if scoring is light or if the disc surface has
severe rust scale.
RECO N D ITIO N if scoring is deep or if runout, thickness
MINIMUM THICKNESS
AFTER REFINISHING
REPLACEMENT
(DISCARD)
THICKNESS
1.230
.980
1.215
.965
Minimum Requirements
The disc brake surfaces must meet the following
specifications:
1.
BOTH SU R FA C ES M UST BE SQUARE WITH
BEARING C U P C E N T E R LIN E W ITH IN .003 T.I.R.
To check, mount the hub and disc to the lathe on
the bearing cups—Do not mount on hub surface
(fig. 64).
2.
FIN ISH
IS TO BE 20-60 M ICR O -IN CH ES AND
B O O T IN S T A L L E R
J -2 2 9 0 4
D U ST
BOOT
Fig. 63 Installing Boot to Caliper
Fig. 6 4 -Hub and Disc Mounting
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
M U ST
NOT
(D IR EC TIO N A L)
3.
4.
5.
BE
5 -3 5
C IR C U M F E R E N T IA L
The disc in Figure 65 has a preferred nondirectional finish that is achieved with a flat
sanding disc.
BOTH SU RFA CES M UST BE FLAT W ITHIN .002
T.I.R.
This specification must be met to prevent surface
taper that could wear shoes on an angle (fig. 66 ).
M UST BE PA R A LLEL W ITH EACH O THER W ITHIN
.003 T.I.R. WHEN C H E C K E D RADIALLY.
Disc surfaces, which are not parallel, can cause
shoes to wear on an angle (fig. 67).
WHEN MOUNTED ON BEA RIN G C U PS, LA TER A L
RUN-OUT M UST NOT E X C E ED .005 T.I.R. AND
M AXIM UM RATE OF C H A N G E M U ST NOT
EX C EED .001 IN 30 4
bearing adjusting nut until all of the play is out
of the bearing. It should be just loose enough to
allow the wheel to turn. Mark the disc with chalk
every 30&deg; (fig. 68 ). Fasten a dial indicator to
some portion of the suspension so that the point
of the stylus contacts the rotor face approx&shy;
imately one inch from the rotor edge. Set the
dial at zero and move the rotor one complete
rotation, checking the indicator as the rotor
moves. After checking the runout, readjust the
wheel bearing (See Section 3).
Proper lateral runout will prevent disc &quot;wobble&quot;
that could knock the piston back into the caliper
bore causing increased pedal travel.
To check lateral runout, tighten the wheel
6.
Fig. 65 -Disc Non-Directional Finish
TO TA L C IR C U M FE R E N T IA L T H IC K N E S S VARIA&shy;
TION AT ANY RAD IUS M UST NOT E X C E ED .0005
IN 360,
Excessive disc thickness variation will cause
brake pedal pulsation.
To check for parallelism, measure the thickness
of the rotor at four or more points around the
circumference of the rotor. All measurements
must be made at the same distance in from the
edge of the rotor.
Place indicators opposite each other and set to
MARK DISC
WITH CHALK
EVERY 30&deg;
MAXIMUM
RUN OUT .005
WITH MAXIMUM
OF .001 IN 30&deg;
Fig. 6 8 -Checking Lateral Run-Out
LIGHT DUTY TRUCK SERVICE MANUAL
5 -3 6 BRAKES
4. Connect the brake lines to the master cylinder.
CAUTIO N: See &quot;Caution&quot; on page 1 of this
section.
5. Fill the master cylinder reservoirs to the levels
shown in Figure 31. Bleed the brake system as
outlined in this section.
6 . If necessary, adjust the brake pedal free play as
outlined in this section.
MASTER CYLINDER OVERHAUL (Fig. 70)
Disassembly
1. Remove the small secondary piston stop screw from
the bottom of the front fluid reservoir of the master
cylinder.
Fig. 6 9 -Checking Circumferential Thickness Variation
zero. As disc is rotated watch each indicator for
proper tolerance. A micrometer could be used
for this check.
MASTER CYLINDER
CAUTIO N: Always use clean brake fluid to
clean any master cylinder parts. Never use
mineral-base cleaning solvents such as gaso&shy;
line, kerosene, carbon-tetrachloridem acetone,
paint thinner or units of like nature as these
solvents deteriorate rubber parts, causing them
to become soft and swollen in an extremely
short time.
Removal
1. Wipe master cylinder and lines clean with a clean
cloth. Place dry cloths below master cylinder areas
to absorb any fluid spillage.
2. Disconnect hydraulic lines at master cylinder. Cover
line ends with clean lint-free material to prevent
foreign matter from entering the system.
3. Disconnect the push rod from the brake pedal.
4. Unbolt and remove the master cylinder from the
dash panel (or power brake booster.)
CAUTIO N: When placing the master cylinder
in a vise, do not tighten too tightly as damage
to the cylinder could result.
2. Place the master cylinder in the vise so that the lock
ring can be removed from the small groove in the
I.D. of the bore. Remove the lock ring and primary
piston assembly. Remove the secondary piston,
secondary piston spring and retainer by blowing air
through the stop screw hole. If air is not available, a
piece of wire may be used. Bend approximately
1/4&quot; of one end of the wire into a right angle.
Hook this end under the edge of the secondary
piston and pull the secondary piston from the bore.
NOTE: The brass tube-fitting insert should
not be removed unless visual inspection
indicates the insert is damaged.
3. To replace a defective insert the following
procedure should be practiced:
a. Place the master cylinder in a vise, so that the
Installation
1. Assemble the push rod through the push rod
retainer, if it has been disassembled.
2. Push the retainer over the end of the master
cylinder. Assemble new boot over push rod and
press it down over the push rod retainer. Slide new
mounting gasket into position. Secure the master
cylinder to the dash panel with mounting bolts.
CAUTIO N : See &quot;Caution&quot; on Page 1 of this
section.
3. Connect the push rod clevis to the brake pedal with
pin and retainer.
Fig. 7 0 -Master Cylinder- Explode
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
outlet holes are up. Enlarge the outlet holes in
the tube seats using a 13/64&quot; drill. Tape a 1/4&quot;
- 20 thread in these holes. Place a heavy washer
over the outlet on the master cylinder and
thread a 1/4&quot; - 20 x 3/4&quot; hex head bolt into the
tube seat. Tighten the bolt until the tube seat is
unseated.
b. A more preferable way to remove a defective
insert involves use of a self-tapping screw and a
claw hammer. With a box-end or socket wrench,
thread a # 6 - 32 x 5/8&quot; long self- tapping screw
into the tube-fitting insert. Using the claw end
of the hammer, remove the screw and insert.
4. Remove the casting from the vise and inspect the
bore for corrosion, pits and foreign matter. Be sure
the outlet ports are clean. Inspect the fluid
reservoirs for foreign matter. Check the bypass and
compensating ports to the master cylinder bore to
determine if they are unrestricted.
5. Remove the primary seal, primary seal protector
and secondary seals from the secondary piston.
Cleaning
Use clean brake fluid to thoroughly clean all reusable
brake parts. Immerse in the cleaning fluid and brush
metal parts with hair brush to remove foreign matter.
Blow out all passages, orifices and valve holes. Place
cleaned parts on clean paper or lintfree clean cloth. If
slight rust is found inside either the front or rear half
housing assemblies, polish clean with crocus cloth or fine
emery paper, washing clean afterwards.
CAUTION: Be sure to keep parts clean until re&shy;
assembly. Re-wash at re-assembly if there is
any occasion to doubt cleanliness - such as
parts dropped or left exposedfor eight hours or
longer.
IF there is any suspicion of contamination or
any evidence of corrosion, completely flush the
vehicle hydraulic brake system in accordance
with this shop manual. Failure to clean the
hydraulic brake system can result in early
repetition of trouble. Use of gasoline, kerosene,
anti-freeze, alcohol or any other cleaner, with
even a trace of mineral oil, will damage rubber
parts.
Rubber Parts
Wipe fluid from the rubber parts and carefully inspect
each rubber part for cuts, nicks or other damage. These
parts are the key to the control of fluid flow. If the unit is
in for overhaul, or if there is any question as to the
serviceability of rubber parts, REPLACE them.
Badly damaged items, or those which would take
extensive work or time to repair, should be replaced. In
case of doubt, install new parts. Do not rely on the brake
unit being overhauled at an early or proper interval.
New parts will provide more satisfactory service, even if
5-37
the brake unit is allowed to go beyond the desired
overhaul period.
Assembly
If the brass tube inserts were removed, place the master
cylinder in a vise so that the outlet holes are up. Position
the new brass tube inserts in the outlet holes, making
sure they are not cocked. The recommended method of
seating these inserts is to thread a spare brake line tube
nut into each outlet and turn the nuts down until the
insert bottoms. Remove the tube nut and check the
outlet hole for loose brass burrs, which might have been
turned up when the insert was pressed into position
Each vehicle application of these cylinders is designed to
produce the correct displacement of fluid from both the
front and rear chambers under normal, failed and
partially failed conditions. Cylinders are designed so that
this variable displacement requirement is controlled
within each bore size by the secondary piston.
Because the pistons vary in length, it is necessary to
mark them with identification rings. It is imperative that
exact replacements be made when servicing the master
cylinders.
With all of the variables to be found in master cylinders,
which look similar externally, it is important that the
complete assemblies be properly identified. For this
purpose a two-letter metal stamp will be found on the
end of each master cylinder. This two-letter stamp
indicates the displacement capabilities of that particular
master cylinder. It is, therefore, mandatory that when
master cylinders are replaced, they are replaced with
cylinders bearing the same two-letter stamp.
1. Place new secondary seals in the two grooves in the
flat end of the secondary piston assembly. The seal
which is nearest the flat end will have its lip facing
toward this flat end. On Delco units, the seal in the
second groove should have its lips facing toward the
end of the secondary piston which contains the
small compensating holes. On Bendix units, the seal
in the second groove is an &quot;O &quot; ring seal.
2. Assemble a new primary seal and primary seal
protector over the end of the secondary piston
opposite the secondary seals, so that the flat side of
the seal seats against the flange of the piston which
contains the small compensating holes.
3. In order to ensure a correct assembly of the
primary piston assembly, a complete primary piston
assembly is included in the repair kits.
4. Coat the bore of the master cylinder with clean
brake fluid. Coat the primary and secondary seals
on the secondary piston with clean brake fluid.
Insert the secondary piston spring retainer into the
secondary piston spring. Place the retainer and
spring down over the end of the secondary piston so
that the retainer locates inside the lips of the
primary seal.
5. Hold the master cylinder with the open end of the
LIGHT DUTY TRUCK SERVICE MANUAL
5 -3 8 BRAKES
bore so that the spring will seat in against the
closed end of the bore. Using a small wooden rod to
push the secondary piston to seat.
6 . Place the master cylinder in a vise with the open
end of the bore up. Coat the primary and
secondary seals on the primary piston with clean
brake fluid. Push the primary piston, secondary
piston stop first, into the bore of the master
cylinder. Hold the piston down and snap the lock
ring into position in the small groove in the I.D. of
the bore.
CAUTION: Do not tighten vise too tightly as
damage to the master cylinder could result.
7. Continue to hold the primary piston down. This will
also move the secondary piston forward and will
ensure that the secondary piston will be forward far
enough to clear the stop screw hole, which is in the
bottom of the front fluid reservoir. The stop screw
is now positioned in its hole and tightened to a
torque of 25-40 inch pounds.
CAUTION: See &quot;Caution&quot; on Page I of this
section.
8 . Install the reservoir diaphragm in the reservoir
cover and install the cover on the master cylinder.
Assemble the bail wire(s) into position to retain the
reservoir cover. The master cylinder is now ready
for &quot;Bench Bleeding&quot;.
MASTER CYLINDER Mounted Booster)
(With Frame
Removal (Fig. 71)
1. Wipe master cylinder and lines clean with a clean
cloth. Place dry cloths below master cylinder to
absorb any fluid spillage.
2. Disconnect hydraulic lines at master cylinder. Cover
line ends with clean, lint-free material to prevent
foreign matter from entering system.
3. Disconnect battery ground strap or stop light wires
and brake warning switch wire.
4. Remove nuts, bolts, washers which fasten master
cylinder to dash. Pull master cylinder straight off
push rod and remove from engine compartment.
5. Remove and discard master cylinder push rod boot.
6 . Remove master cylinder cover and pour out fluid
from reservoir. Pump the remaining fluid out by
depressing piston.
Disassembly
1. Remove cylinder cover bolt and gasket.
2. Lift off reservoir cover and cover seal. Pour out any
excess fluid and stroke piston to force fluid through
outlet ports.
3. Remove piston stop bolt and gasket from bottom of
reservoir housing.
4. Use snap ring pliers and remove retainer ring from
groove in end of cylinder bore.
5. Remove stop plate.
6 . All internal parts should slide easily out of cylinder
bore. If they do not, apply compressed air carefully
at front outlet port. If parts do not remove easily,
examine bore carefully for extensive damage which
may eliminate the possibility of reconditioning the
master cylinder.
Cleaning and Inspection
Clean all parts in clean brake fluid. Inspect cylinder bore
for scratches or corrosion. Minor blemishes can be
removed with crocus cloth or a clean-up hone.
Check by-pass ports in both reservoirs to make sure they
are open and free of burrs.
Remove and discard all rubber parts. All rubber parts
are included in each repair kit.
Assembly
1. Coat all parts with a liberal amount of clean brake
fluid.
2. Install rubber seal cup on secondary piston with cup
lip facing rear (open end of cylinder).
NOTE: All other cup lips face in the opposite
direction (closed end of cylinder.)
3. Stack and install secondary piston spring, pressure
cup and piston in cylinder bore.
4. Install piston stop bolt and gasket, making sure
screw enters cylinder bore behind rear of piston.
5. Assemble and install primary piston parts in
cylinder bore.
6 . Install stop plate in cylinder bore.
7. Compress all parts in cylinder bore and install
retainer ring in groove.
8 . Install reservoir cover and seal.
Installation
1. Assemble new boot on brake pedal push rod.
2. Place master cylinder in position in engine
compartment. Make certain that push rod and boot
are in proper position.
3. Fasten master cylinder to dash with nuts, bolts, and
washers.
CAUTION: See &quot; Caution &quot; on Page 1 o f this
section.
4. Connect brake lines to master cylinder.
CAUTIO N: See &quot; Caution &quot; on Page 1 of this
section.
5. Fill the reservoir with recommended brake fluid to
level shown in Figure 31.
6 . Follow instructions under heading of &quot;Bleeding
Brakes&quot;.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -3 9
4
1 Primary Piston Seal Cup
2 Primary Piston
3 Cover Seal
4 Reservoir Cover
5 Gasket
6 Cover Bolt
7 Intake Port
8 By-Pass Port
9 Reservoir Housing
10 Tube Seat
11 Secondary Piston Return
Spring
12 Secondary Piston Pressure
Cup
13 Floating Secondary Piston
14 Secondary Piston Seal Cup
15 Gasket
16 Stop Bolt
17 Prim ary Return Spring
Retainer
18 Prim ary Return Spring
19 Prim ary Piston Stop Pin
20 Primarv Piston Pressure
Cup
21 Stop Plate
22 Retainer Ring
Fig. 71--Frame Mounted Booster Master Cylinder
7. If necessary, adjust the brake pedal free play as
directed.
8 . Connect battery ground strap or stop light wires
and brake warning switch wire (whichever was
disconnected at removal).
9. Test brakes and make any necessary adjustments if
operation is not satisfactory.
Bleeding Tool (Fig. 72)
A special tool for bleeding the frame mounted booster
master cylinder is shown in Figure 72.
It will be necessary for the technician to install his own
bleeder adapter fitting to this tool. When bleeding the
system, always bleed the frame mounted boosters before
bleeding any wheel cylinders.
BENCH BLEEDING MASTER CYLINDER
1. Install plugs in both outlet ports.
NOTE: Plastic plugs that come with a
Fig. 72 -Tool J-23339 Installed
LIGHT DUTY TRUCK SERVICE MANUAL
/
5 -4 0 BRAKES
replacement cylinder are recommended for
this operation.
2. Clamp the master cylinder in a bench vise with the
front end tilted slightly down.
CAUTION: Do not tighten vise too tightly as
damage to the master cylinder could result.
3. Fill both reservoirs with clean brake fluid.
4. Insert a rod with a smooth round end to the
primary piston and press in to compress the piston
return spring.
5. Release pressure on rod. Watch for air bubbles in
the reservoir fluid.
6 . Repeat Step 5 as long as bubbles appear.
7. Reposition master cylinder in vise so that the front
end is tilted slightly up.
8 . Repeat Steps 4-5-6.
9. Install diaphragm and cover on reservoir.
BRAKE COMBINATION VALVE
Metering, Warning and Proportioning (Fig.
73)
NOTE: The brake combination valve is a
non-adjustable, non-serviceable valve. If
defective it must be replaced.
Function
position (not allowed to close). This can be
accomplished by installing Tool J-23709
under the mounting bolt and depressing the
pin in the end of the valve. Be sure to re&shy;
torque the mounting bolt after removing
Tool J-23709 (fig. 29).
Warning Switch
The warning switch is the pressure differential type. It is
wired electrically to the warning lamp on the instrument
panel to warn the vehicle operator of a pressure
differential between the front and rear hydraulic systems.
Once the switch is activated &quot;on&quot;, it will not &quot;reset&quot; until
the defect in the hydraulic system has been repaired.
Hydraulic reset to the &quot;off&quot; position occurs with the
application of equal front and rear pressures.
Proportioning Valve
The function of this valve is prevent premature rear
wheel slide. Line pressure is allowed to increase normally
up to a certain point (determined by vehicle weight and
braking distribution). When the predetermined pressure
is reached, the valve begins to function and limit the
amount of increase in hydraulic pressure passed to the
rear brakes. This prevents the rear brakes from locking
up before the full effective braking effort is produced by
the front disc brakes.
NOTE: In the event of &quot;front hydraulic
system failure&quot; the proportioning valve has a
&quot;by-pass&quot; feature that assures full system
pressure to the rear brakes.
Metering Valve
Removal
This section of the valve operates to &quot;hold-off&quot; hydraulic
flow to the front disc brakes until a predetermined
pressure is reached. This &quot;hold-off&quot; action allows the
rear drum brakes to build up sufficient hydraulic
pressure to overcome the force of their retracting
springs. This metering or hold-off valve then provides
for balanced braking.
NOTE: When bleeding the brakes; the pin in
the end of the metering portion of the
combination valve must be held in the open
1. Disconnect electrical lead.
2. Place dry rags below valve to absorb any fluid
spillage.
3. Wipe off any dirt and disconnect hydraulic lines
from valve—cover open lines to prevent foreign
matter from entering the system.
4. Remove mounting screws and remove valve.
Installation
1. Make sure new switch is clean and free of lint. If
any doubt exists, wash the switch in clean brake
fluid.
2. Place new switch in position and secure with screws.
CAUTION: See &quot;Caution&quot; on Page 1 of this
SWITCH
TERMINAL
FROM MASTER
CYLINDE
FROM MASTER CYLINDER
section.
TO REAR
BRAKES
TO FRONT
BRAKES
3. Connect hydraulic lines to valve.
CAUTION: See &quot;Caution&quot; on Page
1 of this
section.
4. Connect switch electrical lead.
5. Bleed the brake system.
Fig. 73-Combination Valve
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
Brake Warning Light Checking
1. Set parking brake and turn the ignition key to
&quot;ON&quot;.
2. Warning lamp should light.
3. If lamp does not light, bulb is burned out or
electrical circuit is defective.
4. Turn ignition key off.
5. Replace bulb or repair circuit as necessary.
Testing Warning Switch
1. Raise vehicle on a hoist and attach a bleeder hose
to a rear brake bleed screw and immerse the other
end of hose in a container partially filled with clean
brake fluid. Be sure master cylinder reservoirs are
full.
NOTE: When bleeding the brakes; the pin in
the end of the metering portion of the
combination valve must be held in the open
position (not allowed to close). This can be
accomplished by installing Tool J-23709
under the mounting bolt and depressing the
pin a slight amount. Be sure to re-torque the
mounting bolt after removing Tool J-23709
(fig- 29).
CAUTIO N: See &quot; Caution&quot; on Page 1 of this
section.
2. Turn ignition key &quot;ON&quot;. Open bleed screw while
helper applies heavy pressure to brake pedal.
Warning lamp should light. Close bleed screw
before helper releases pedal.
NOTE: To &quot;reset&quot; switch, apply heavy pedal
force. This force will apply hydraulic pressure
which re-centers the switch contact.
3. Attach bleeder hose to front brake bleed screw and
repeat Step 2.
4. Turn ignition key off. See Note under Step 2.
5. Lower vehicle to floor.
NOTE: If warning lamp does not light
during Steps 2 and 3 but does light when the
parking brake is set, warning light switch is
defective. Do not attempt to repair switch. A
defective switch must be replaced with a new
combination valve assembly.
5-41
boosters have an electrical switch that senses pedal
travel. This switch will illuminate the lamp on the
instrument panel whenever the brake pedal is in excess
of 5.10 inches.
Removal
1. Loosen the nut (at the switch) on the failure
warning switch push rod and drop the push rod out
of the way.
2. Remove the switch electrical lead.
3. Remove the two switch mounting screws and
remove switch.
Installation
1. Install the switch to the brake pedal bracket with
two screws and install the electrical lead.
2. Check the length of the failed switch push rod to
see that it is as described in Figure 74.
3. Adjust the switch so that the warning light will be
on after 5.10&quot; pedal pad travel in the following
manner.
NOTE: The brake pedal to master cylinder
push rod will have to be removed to make
test to determine if the switch is properly set.
Adjust the brake pedal push rod travel as
described in this section upon completion of
installation.
4. With brake pedal hard against rubber bumper (A),
rotate brake failure warning switch lever (B)
forward and insert the preassembled push rod (C)
in the switch and brake pedal and lock in place.
CAUTIO N: Caution should be taken to prevent
air from entering system during checks on
switch.
The recommended checking interval should be 24
months or 24,000 miles, any time major brake work is
done or any time a customer complains of excessive
pedal travel.
BRAKE TRAVEL WARNING SWITCH (Fig.
74)
Vehicles with frame mounted vacuum over hydraulic
LIGHT DUTY TRUCK SERVICE MANUAL
5 -4 2 BRAKES
I f Switch Circuit is Closed
a. Rotate switch bracket rearward until switch &quot;just
opens&quot; (light off).
b. Hold switch bracket in this position and tighten
bolt (D). Switch should close (light on) at 5.10&quot;
brake pedal pad movement from full back.
I f Switch Circuit is Open
a. Rotate switch bracket forward until switch &quot;just
closes&quot; (light on).
b. Hold switch bracket in this position and tighten
bolt (D).
BRAKE PEDAL—SERVICE BRAKE (Fig. 75)
NOTE: The brake pedal is an integral design
with the clutch pedal (except automatic
transmission), necessitating the removal of
the clutch pedal before removing the brake
pedal.
Removal
1. Remove the pull back spring from the body or
brake pedal support bracket.
2. Manual Transm ission Vehicles-Rem ove the clutch
pedal as outlined under &quot;Clutch Pedal&quot; in Section
7.
Automatic Transm ission Vehicles-Rem ove pedal
pivot bolt nut or pivot pin retainer and remove bolt
or pin and bushings.
3. P Models-Remove the sleeve assembly screw
attachment and remove sleeve.
4. Disengage the push rod from the master cylinder
and remove the pedal.
Inspection
Clean all parts and inspect for wear, cracks or any other
damage that might impair operation; replace if required.
Installation
Reverse the above procedure and make certain the brake
pedal is secure and adjusted properly before operating
the vehicle. Lubricate pedal pivot bushings and pivot
pin, bolt or sleeve with Delco Brake Lube #5450032 (or
equivalent).
CAUTIO N: See &quot; Caution&quot; on Page 1 of this
section.
PARKING BRAKE PEDAL OR HANDLE
Removal (Fig. 76)
1. Place parking brake pedal or handle in the released
position.
2. Remove nuts from the engine compartment on C, K
and G models or bolts from mounting bracket on P
models.
3. Disconnect the release handle rod at the parking
brake assembly end (C-K models).
4. Remove the bolts from the underside of the dash
and lower the brake assembly.
NOTE: Take notice of the spacers on P
models for reinstallation.
5. Remove the clevis pin and disconnect the cable
from the brake assembly.
Installation
Reverse the removal procedure. Torque all bolts and
nuts. After installing the clevis pin, use a new cotter pin
to secure the clevis pin. Adjust the cable if necessary as
outlined under &quot;Maintenance and Adjustments&quot;.
CAUTIO N: See &quot;Caution&quot; on Page 1 of this
section.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -4 3
VIEW
C-K MODELS
POOO (42) MODELS
(v
G MODELS
iew
P300 (32) MODELS
Fig. 76-Parking Brake Assembly-Typical
PARKING BRAKE CABLES
Refer to Figure 77 for routing of cables.
i
PARKING BRAKE-PROPELLER SHAFT—
(Internal Expanding)
Removal (Fig. 78)
1. Remove the propeller shaft; see Section 4.
2. Remove the brake drum.
NOTE: It may be necessary to back off the
shoe adjustment before removing the drum.
3. Remove the two pull back springs.
4. Remove the guide plate from anchor pin.
5. Remove shoe hold down cups, springs, and washers
from hold down pins—remove pins.
6 . Pull brake shoe and lining assemblies away from
anchor pin and remove the strut and spring.
7. Lift the brake shoes and linings with the adjusting
nut and bolt and connecting spring off the flange
plate.
8 . Move the shoes toward each other until the
adjusting bolt and connecting spring drop off.
9. Remove the clip holding the brake lever to the
primary shoe (shoe with short lining).
10. Compress the spring on the brake cable and remove
the cable from the lever.
11. If necessary to remove the anchor pin, straighten
the washer from pin hex and reinforcement.
Remove reinforcement and washer with anchor pin.
12. If necessary to remove the cable, compress tangs on
cable and pull assembly out of the hole in the
flange plate.
13. If necessary to remove the flange plate, remove the
transmission flange nut and transmission output
flange. Remove bolts holding the flange plate to
bearing retainer and remove the flange plate.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -4 4 BRAKES
C MODELS
G MODELS
P MODELS
Fig. 77-Parking Brake System
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5-45
RETURN
SPRINGS
WAVE
WASHER
BRAKE
LEVER
HOLD
DOWN
PIN
DRUM
HOLD D O W N
WASHER. SPRING , CUP
BACKING
PLATE
BRAKE
CABLE
Fig. 7 8 -Internal Expanding Brake Components
Inspection
Replace any worn or broken parts.
Installation
1. Place the flange plate in position on the rear
bearing retainer and fasten with four bolts. Torque
bolts to 24 foot pounds.
CAUTION:
See &quot;Caution&quot; on Page I of this
section.
2. Install transmission output flange on spline of
mainshaft and fasten with flange nut. Torque nut to
100 foot pounds.
CAUTION: See &quot; Caution&quot; on Page 1 of this
section.
3. Install cable assembly from back of flange plate.
Push retainer through hole in flange plate until
tangs securely grip the inner side of the plate.
4. Place washer and reinforcement over the threaded
end of anchor pin. Hold anchor pin nut (flat side
against flange on flange plate) in position behind
flange plate and insert threaded end of anchor pin
from front side. Thread the anchor pin into nut and
tighten securely (140 foot pounds torque). Bend
tang of washer over reinforcement and side of
washer over hex of anchor pin.
CAUTION: See &quot; Caution&quot; on Page 1 of this
section.
5. Install lever on cable by compressing spring and
inserting cable in channel of lever. Release spring.
6 . Install primary shoe (short lining) to lever as
follows: Place pin in lever, place washer on pin and
push pin through hole in primary shoe. Fasten
parts together by installing the clip in groove of
pin.
CAUTION:
See &quot;Caution&quot; on Page 1 of this
section.
7. Fasten two brake shoes and linings together by
installing connecting spring. Move the shoes toward
each other and install adjusting screw.
8 . Lubricate the flange plate contact surfaces with a
very light coat of Delco Brake Lube #5450032 (or
equivalent).
9. Place shoe and linings in position on flange plate.
NOTE: When facing the brake assembly, the
shoe with the short lining should be to the
left with the lever assembled to it.
10. Pull brake shoes apart and install strut lever and
spring between them. The loop on the strut spring
should be in the &quot;up&quot; position.
11. Install hold down pins, washers, springs and cups
from flange plate to shoes.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -4 6 BRAKES
12. Place guide plate on anchor pin.
13. Install pull back springs.
14. Remove the &quot;knock out&quot; plug (if necessary) and
install a new metal plug in the brake drum
adjusting hole.
15. Install the brake drum.
16. Install the propeller shaft.
REAR BRAKES RPO H-22 (Fig. 79)
Brake shoe adjustment takes place when brakes are
applied with a firm pedal effort while the vehicle is
backing up. Applying the brakes moves actuators which
turn the star wheels and rotate the adjusting screws
outward from the anchor brackets. This action adjusts
the shoe until clearance between the lining and drum is
within proper limits.
Should low pedal heights be encountered, it is
recommended that numerous forward and reverse stops
be performed with a firm pedal effort until a satisfactory
pedal height results.
Retracting Self Adjusters
Access holes are located in the flange plate. These holes
are for service purposes in the event retracting of the
brake shoes is required to remove the drum. In order to
back off the adjuster, insert a screwdriver, index a corner
of the screwdriver blade with the hole in the actuating
lever and hold the lever away from the star wheel. Using
a brake adjusting tool, back off the star wheel.
Brake Drums, Shoes and Linings
3. Using Tool J-22348, remove the brake shoe pull
back springs (fig. 80).
4. Loosen the actuating lever cam cap screw and while
holding the star wheel end of the actuating lever
past the star wheel, remove the cap screw and cam.
5. Remove the brake shoe hold down springs and pins
by compressing the spring with Tool J-22348 and, at
the same time, pushing the pin back through the
flange plate toward the tool. Then, keeping the
spring compressed, remove the lock from the pin
with a magnet (fig. 81).
6 . Lift off the brake shoe and self adjuster as an
assembly.
7. The self adjuster can now be removed from the
brake shoe by removing the hold down spring and
pin.
NOTE: The actuating lever, override lever
and spring are an assembly. It is recom&shy;
mended that they not be disassembled for
service purposes unless they are broken. It is
much easier to assemble and disassemble the
brakes leaving them intact.
8 . Thread the adjusting screw out of the anchor
support and remove and discard the friction spring.
9. Clean all dirt out of brake drum. Inspect drums for
roughness, scoring or out-of-round. Replace or
recondition drums as necessary.
NOTE: See Section on &quot;BRAKE DRUMS&quot;.
10. Carefully pull lower edges of wheel cylinder boots
Removal
1. Raise the vehicle on a hoist.
2. Retract self adjusters if necessary and remove
brake drums.
ANCHOR
SUPPORT x
A C T U A T IN G LEVER
CAM
A C T U A T IN G
LEVER LINK
FRICTIO N
SPRING
OVER RIDE
' LEVER
OVER RIDE
SPRING
RETURN
SPRING
HO LD D O W N
PIN
STAR
W HEEL
A C T U A T IN G
LEv e r
Fig. 79 -Rear Brake-Used with RPO H-22
Fig. 8 0 -Removing Pull Pack Spring with Tool
J-22348
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -4 7
Fig. 81-Removing Hold Down Pins Using J-22348
away from cylinders. If brake fluid flows out,
overhaul of the wheel cylinders is necessary.
NOTE: A slight amount of fluid is nearly
always present and acts as a lubricant for the
piston.
11. Inspect flange plate for oil leakage past axle shaft
oil seals. Install seals if necessary.
12. Check all flange plate attaching bolts to make sure
they are tight (150 ft. lbs. torque). Clean all dirt
and rust from shoe contact faces on flange plate
using emery cloth.
13. Thoroughly clean adjusting screws and threads in
the anchor brackets.
Fig. 82-Brake Shoe and Self Adjuster Assembly
Installation
1. Put a light film of Delco Brake Lube #5450032 (or
equivalent) on shoe bearing surfaces of brake
flange plate and on threads of adjusting screw.
2. Thread adjusting screw completely into anchor
bracket without friction spring to be sure threads
are clean and screw turns easily. Then remove
screw, position a new friction spring on screw and
reinstall in anchor bracket.
CAUTION:
section.
See &quot;Caution&quot; on Page 1 of this
3. Assemble self adjuster assembly to brake shoe and
position actuating lever link on override lever.
4. Position hold down pins in flange plate.
5. Install brake shoe and self adjuster assemblies onto
hold down pins, indexing ends of shoes with wheel
cylinder push rods and legs of friction springs.
NOTE: Make sure the toe of the shoe is
against the adjusting screw (fig. 82).
6 . Install cup, spring and retainer on end of hold
down pin. Using Tool J-22348, compress the spring.
With spring compressed, push the hold down pin
Fig. 83 Measuring Points for Shoe Centering
back through the flange plate toward the tool and
install the lock on the pin.
7. Using Tool J-22348, install brake shoe return
springs.
8 . Holding the star wheel end of the actuating lever as
far as possible past the star wheel, position the
adjusting lever cam into the actuating lever link
and assemble with cap screw.
9. Check the brake shoes for being centered by
measuring the distance from the lining surface to
LIGHT DUTY TRUCK SERVICE MANUAL
5 -4 8 BRAKES
ACTUATING LEVER---------►
TOP VIEW
ACTUATING LEVER
END VIEW
Fig. 84 -Positioning Actuator Lever
the edge of the flange plate at the points shown in
Figure 83. To center the shoes, tap the upper or
lower end of the shoes with a plastic mallet until
the distances at each end become equal.
10. Locate the adjusting lever .020&quot; to .039&quot; above the
outside diameter of the adjusting screw thread by
loosening the cap screw and turning the adjusting
cam.
NOTE: To determine .020&quot; to .039&quot;, turn the
adjusting screw 2 full turns out from the fully
retracted position. Hold a .060&quot; plug gauge
(from J-9789-01 Universal Carburetor Gauge
Set) at a 90&deg; angle with the star wheel edge of
the actuating lever. Turn the adjusting cam
until the actuating lever and threaded area
on the adjusting screw just touch the gauge
(figs. 84 and 85).
Fig. 85-Pull Gauge Positioning for Correct Actuator
Lever Adjustment
11. Secure the adjusting cam cap screw and retract the
adjusting screw.
12. Install brake drums and wheels and remove vehicle
from jack stands.
13. Adjust the brakes by making several forward and
reverse stops until a satisfactory brake pedal height
results.
D IA G N O S IS
INSPECTION
At a reasonably frequent interval, the brake system
should be inspected for pedal reserve, which is the
clearance between the pedal pad and the fioorpan.
Inspection should be made with the brake pedal firmly
depressed while the brakes are cold. Pedal reserve on
manual brake vehicles is usually not less than 2-1/4&quot;. On
power brake-equipped vehicles, the pedal reserve is
usually not less than 1- 1/ 2 &quot;.
NOTE: Heat generated by high speed stops
will expand brake drums and increase shoe
clearance, thereby permitting the pedal pad
to go closer to the fioorpan than when the
brakes are cold.
Brake shoe linings should not be permitted to wear down
until rivets or shoes contact drums because the drums
could be scored. As the vehicle mileage approaches the
point where relining may be required it is advisable to
remove one or more drums for inspection of linings in
order to avoid the possibility of damaging brake drums.
LIGHT DUTY TRUCK SERVICE MAmJAL
BRAKES
PRELIMINARY CHECKS
External Conditions That Affect Performance
In addition to previously mentioned conditions, the
following external conditions may affect brake perform&shy;
ance and should be corrected before work is done on the
brake mechanism.
Tires
Tires having unequal contact and grip on the road could
cause unequal braking. Tires should be equally inflated
and tread pattern of right and left tires should be
approximately equal.
Loading
When the vehicle has unequal loading, the most heavily loaded
wheels require more braking power than others.
Shock Absorbers
Faulty shock absorbers that permit bouncing of the vehicle on
quick stops may give the erroneous impression that brakes are
too severe.
General Checks
NOTE: If a damaged component or malfunc&shy;
tion is discovered while making any of the
following brake system checks, repairs must
be made before attempting to continue with
additional diagnosis.
1. Inspect for excessive tire tread wear and indications
of front suspension misalignment. Check tire
pressures and for improperly adjusted or worn
wheel bearings. Any of these conditions can result
in an improper diagnosis.
2. Check master cylinder fluid level. If low, refill to the
proper level, pressurize the system, and make an
inspection of the entire brake system for leakage.
Wheel cylinder leakage can frequently be detected
by the presence of brake fluid on the inboard side
of the wheel and tire.
3. Power Brake:
a. With transmission in Park, stop the engine, and
exhaust all vacuum in the system by depressing
the pedal several times.
b. Depress the brake pedal and hold it in the apply
position for one minute with approximately 20
lbs. pedal force. If the pedal gradually falls
away or the brake warning light comes on, it is
an indication that the hydraulic system is
leaking or that there is a malfunction in the
master cylinder. Check all tubing, hoses, wheel
cylinders, calipers and connections for leakage
before replacing the master cylinder.
c. If the brake pedal feels spongy, it is an
indication of air in the hydraulic system. Bleed
the air from the system and recheck the pedal
feel.
NOTE: Steps (b) and (c) may also be used to
5 -4 9
check for leakage or the presence of air in a
non-vacuum powered brake system.
d. Depress the brake pedal and start the engine. If
the vacuum system is operating, the brake pedal
will tend to fall away when the engine starts and
less pedal pressure will be needed to hold it in
the applied position. If no action is felt when
the engine starts, the vacuum system is
inoperative.
ROAD TESTING
CAUTION: A road test should be made only
when the operator is sure that the brakes will
stop the vehicle.
Road tests are necessary to check brakes for safe, quiet
performance. Preliminary inspection should be made in
the shop as outlined in the preceding paragraphs. The
following tests will aid in the evaluation of brake
performance and the need for service. They should be
conducted on dry, clean, reasonably smooth and level
roadway. Use care not to induce fade unintentionally
with continuous applications during test. Refer to the
Troubleshooting Chart for causes and remedies for
trouble which may be discovered during testing.
WARNING: Before driving any vehicle, push
the brake pedal to make sure it will not
bottom. Next, make a series of slow speed
stops to determine if the brakes are safe for
driving.
Low Speed Test for Effectiveness, Pulls and
Noise
fkS .
Make light and medium stops at from 10 to 15 MPH.
Bring the vehicle to a complete stop each time. Observe
the effort required to make each stop. Is it too light
(grabby) satisfactory or too hard? Check for pulls.
Unequal front brakes will cause pulls in the direction of
the brake doing the most work. Unequal rear brakes may
not cause noticeable pulling during low speed stops.
Check for noise. Open the windows and turn off all
accessories and listen to determine the type of noise and
the wheel from which it is coming.
NOTE: Driving along a wall when applying
brakes will make noises more audible.
High Speed Test for Roughness or
Pulsations
Make light stops from 60 MPH or maximum legal speed.
Check for roughness or pulsations by pedal feel and
vehicle vibration.
High Speed Test for Effectiveness, Pulls and
Noise
Make hard stops (just short of skid) from 60 MPH. Bring
LIGHT DUTY TRUCK SERVICE MANUAL
5 -5 0 BRAKES
the vehicle to a complete stop each time. Do not repeat
stops within two miles of each other to avoid high brake
temperatures. Observe the effort required to make each
stop. Is it too light (grabby), satisfactory or too hard?
Check for pulls. Unequal brakes will cause pulls in the
direction of the brake doing the most work. Check for
noise to determine the type and the wheel from which it
is coming.
High Speed Test for Fade
NOTE: Fade is a temporary reduction of
brake effectiveness resulting from heat.
Make three hard stops (just short of skid) from 60 MPH
at 1/2 mile increments or just as fast as possible. Check
for pulls and observe the effort required to make the
stops. These should be made without strenuous effort.
Check pedal reserve after each stop.
High Speed Test for Delayed Fade
After making previous fade test, let the vehicle stand for 10
minutes. Then, accelerate quickly to 60 MPH and make one
hard stop, just short of a skid. Check for pulls and observe the
effort required to make the stop. Check pedal reserve.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5-51
DIAGNOSIS—DRUM BRAKES
LOW PEDAL OR PEDAL GOES TO TOE BOARD
Probable Cause
Remedy
1 . Excessive clearance between l i n i n g s and drum.
1 . A djust brakes.
2. Automatic a d ju s te rs not working.
2. Make forward and reverse stops; i f pedal stays low,
r e p a i r f a u l t y a d ju s te r s .
3. . Leaking conduits.
3. Repair or repla ce f a u l t y p a rts .
4. Leaking wheel c y l i n d e r .
4. Overhaul wheel c y l i n d e r , as o u t lin e d p re v io u s ly in
t h i s s e c tio n .
5. Leaking master c y l i n d e r .
5. Overhaul master c y l i n d e r as o u t lin e d p re v io u s ly in
t h i s s e c tio n .
6. A i r in system.
6. Bleed system.
7. Plugged master c y li n d e r f i l l e r cap.
7. Clean f i l l e r cap vent hole s; bleed system.
8. Improper brake f l u i d .
8. Flush system and r e f i l l w ith GM Hydraulic Brake F lu id
Supreme No. 11 (o r e q u i v a le n t ) .
9. Low f l u i d l e v e l .
9. F i l l r e s e r v o ir w ith GM Hydraulic Brake F lu id Supreme
No. 11 (o r e q u i v a le n t ) ; bleed system.
SPRINGY, SPONGY PEDAL
Probable Cause
Remedy
1 . A i r trapped in h y d ra u lic system.
1 . Remove a i r by ble e din g.
2. Improper brake f l u i d .
2. Flush and bleed system using GM Hydra ulic Brake F lu id
Supreme No. 11 (o r e q u iv a le n t ) .
3. Improper l i n i n g thickness or lo c a t io n .
3. I n s t a l l new l i n i n g o r replace shoe and l i n i n g .
4. Drums worn too t h i n .
4. Replace drums.
5. Master c y li n d e r f i l l e r vent clogged.
5. Clean vent or repla ce cap; bleed brakes.
E X C E SSIV E PED A L PRESSU RE REQ U IRED TO STOP V E H IC LE
Probable Cause
Remedy
1 . Brake adjustment not c o r r e c t .
l
2. I n c o r r e c t l i n i n g .
2. I n s t a l l new l i n i n g s .
3. Grease or f l u i d soaked l i n i n g .
3. Repair grease seal or wheel c y l i n d e r .
1in in g s .
4. Improper f l u i d .
.
4.
A djust the brakes.
In s ta ll
new
Flush out system; f i l l w ith GM Hydraulic Brake F lu id
Supreme No. 11 (o r e q u i v a le n t ) ; bleed system.
5. Frozen master or wheel c y li n d e r p is to n s .
5. Overhaul master or wheel c y li n d e r s as o u t lin e d
p r e v io u s ly in t h i s s e c tio n .
6. Brake pedal bindin g on s h a f t .
6. L u b rica te w ith Delco Brake Lube #5450032 (or e q u iv a le n t).
LIGHT DUTY TRUCK SERVICE MANUAL
5 -5 2 BRAKES
DIAGNOSIS—DRUM BRAKES
EXCESSIVE PEDAL PRESSURE REQUIRED TO STOP VEHICLE (CONT.)
Remedy
Probable Cause
7. Glazed 1in in g s.
7. Sand surface o f l i n i n g s .
8. Bellmouthed, barrel-shaped or scored drums.
8. Replace or resu rfa ce drums in l e f t and r i g h t hand p a ir s .
LIGHT PEDAL PRESSURE-BRAKES TOO SEVERE
Probable Cause
Remedy
1. Brake adjustment not c o r r e c t.
1. A djust the brakes.
2. Loose fla n ge p la te on f r o n t axle .
2. Tighten p la te s .
3. A small amount o f grease or f l u i d on l i n i n g s .
3. Replace the l i n i n g s .
4. Charred l i n i n g s .
4. Replace the 1in in g s .
5. In c o r r e c t 1 in i r i g .
5. I n s t a l l new l i n i n g s .
6. Wheel bearings loose.
6. Adjust wheel bearings.
7. Linin g loose on shoe.
7. Replace l i n i n g o r shoe and l i n i n g .
8. Excessive dust and d i r t in drums.
8. Clean and sand drums and l i n i n g s .
9. Bellmouthed, barrel-shaped or scored drums.
9. Turn drums in p a irs or repla ce.
BRAKE PEDAL TRAVEL DECREASING
Probable Cause
Remedy
1. Master c y li n d e r compensating p o rt plugged.
1. Open, use a i r or .015 w ir e .
2. Swollen cup in master c y li n d e r .
2. Replace rubber p a r ts . Flush system. R e f i l l w ith GM
Hydraulic Brake F lu id Supreme No. 11 (or e q u iv a le n t ) .
3. Master c y li n d e r p isto n not re tu r n in g .
3. Overhaul master c y li n d e r as o u t lin e d p re v io u s ly in
t h i s s e c tio n .
4. Weak shoe r e t r a c t i n g s pring s.
4. Replace spring s.
5. Wheel c y li n d e r pistons s t i c k i n g .
5. Overhaul wheel c y li n d e r as o u t lin e d p r e v io u s ly in
t h is s e c tio n .
Remove any b u rr in bore.
PULSATING BRAKE PEDAL
Remedy
Probable Cause
1. Drums o u t-o f-ro u n d .
1. Re finis h drums.
2. Loose brake drum on hub.
2. Tighten.
3. Worn or loose wheel bearings.
3. Replace or a d ju s t.
4. Bent rear axle .
4. Replace axle.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -5 3
DIAGNOSIS—DRUM BRAKES
‘ BRAKES FADE
Probable Cause
Remedy
1. I n c o r r e c t l i n i n g .
1. Replace w ith new l i n i n g .
2. Thin drum.
2. Replace drums.
3. Dragging brakes.
3. A djus t or c o r r e c t cause.
*Fade is a temporary re d u c tio n o f brake e ffe c tiv e n e s s r e s u l t i n g from heat.
ALL BRAKES DRAG WHEN ADJUSTMENT IS KNOWN TO BE CORRECT
Probable Cause
Remedy
1. Pedal does not r e t u r n to s top.
1. Lu brica te the pedal w ith Delco Brake Lube #5450032
(or e q u i v a l e n t ) .
2.
2. Replace rubber pa rts and f i l l w ith GM Hydra ulic Brake
F lu id Supreme No. 11 (or e q u iv a le n t ) .
Improper f l u i d .
3. Compensating or bypass p o r t o f master c y l i n d e r
closed.
3. Open w ith compressed a i r .
4. Use o f i n f e r i o r rubber p a r ts .
4. Overhaul wheel and/or master c y li n d e r using new Delco
k i t s (or e q u i v a l e n t ) .
ONE WHEEL DRAGS
Probable Cause
1
.
Weak or broken shoe r e t r a c t i n g s pring s.
2. Brake shoe to drum clearance too small or the brake
shoe e cc e n tric is not adjusted p ro p e rly .
Remedy
1
.
Replace the d e f e c t iv e brake shoe springs and l u b r i c a t e
the brake shoe ledges w ith Delco Brake Lube #5450032
(or e q u iv a le n t ) .
2. A d ju st.
3. Loose wheel be arings.
3. A djus t wheel bearings.
4. Wheel c y li n d e r pisto ns cups swollen and d i s t o r t e d
or the pistons stu ck.
4. Overhaul c y lin d e r s as o u t lin e d p re v io u s ly in t h is
s e c tio n .
5. Pistons s t i c k i n g in wheel c y l i n d e r .
5. Clean or repla ce p is to n s ; clean c y li n d e r bore.
6. Drum o u t - o f - r o u n d .
6. Grind or t u rn both rea r drums.
7. O bstructio n in l i n e .
7. Clean ou t or rep la ce.
8. Loose anchor pin .
8. A djust and t ig h t e n lo ck nut.
9. D is to rte d shoe.
10. Defe ctiv e 1in in g .
9. Replace
10. Replace w ith new l i n i n g .
LIGHT DUTY TRUCK SERVICE MANUAL
5 -5 4 BRAKES
DIAGNOSIS—DRUM BRAKES
REAR BRAKES DRAG
Remedy
Probable Cause
1. Maladjustment.
1. Adjust brake shoes and parking brake mechanism.
2. Parking brake cables frozen .
2. Lu bricate w ith Delco Brake Lube #5450032 (or
e q u i v a le n t ) .
V E H IC LE P U LLS TO ONE SID E
Probable Cause
Remedy
1.
Grease or f l u i d soaked l i n i n g .
1.
Replace w ith new l i n i n g s .
2.
Adjustment not c o r r e c t .
2.
Adjust the brakes.
3.
Loose wheel bearings, loose fla n g e p la te on rear
axle or f r o n t axle or loose sp ring b o lt 6 .
3.
A djus t the wheel bearing, tig h t e n the fla nge
p la t e on the re a r and f r o n t axles and t ig h t e n
spring b o lt s .
4.
Linings not o f s p e c ifie d kind or primary and
secondary shoes reversed.
4.
I n s t a l l new 1in in g s .
5.
T ires not p ro pe rly i n f l a t e d or unequal wear o f
tread . D i f f e r e n t tread non-skid design.
5.
I n f l a t e the t i r e s to recommended pressures.
Rearrange the t i r e s so t h a t a p a ir o f nonskid tread surfaces o f s i m i l a r design
and equal wear w i l l be i n s t a l l e d on the f r o n t
wheels, and another p a ir w ith l i k e tread w i l l
be i n s t a l l e d on the rea r wheels.
6.
Linin gs charred.
6.
Replace w ith new l i n i n g .
7.
Water, mud, e t c . , in brakes.
7.
Remove any f o r e ig n m aterial from a l l o f the
brake parts and the in s id e o f the drums.
L u bricate the shoe ledges and the re a r brake
cable ramps w ith Delco Brake Lube #5450032
(o r e q u i v a l e n t ) .
8.
Wheel c y li n d e r s t i c k i n g .
8.
Overhaul or repla ce wheel c y l i n d e r .
9.
Weak or broken r e t r a c t i n g s pring s.
9.
Check s p r in g s -re p la c e bent, open-coiled or
cracked s pring s.
10.
Out-of-round drums.
10.
Resurface or replace drums in l e f t and r i g h t
hand p a irs (both f r o n t and both r e a r ) .
11.
Brake dragging.
11.
Check f o r loose l i n i n g .
12.
Weak chassis springs or loose &quot;U&quot; b o lt s .
12.
Replace springs or t ig h t e n &quot;U&quot; b o l t s .
13.
Loose s t e e rin g .
13.
Repair and a d ju s t.
14.
Unequal camber.
14.
A djus t to s p e c if ic a t i o n s .
15.
Clogged or crimped h y d r a u lic l i n e .
15.
Repair or replace l i n e .
16.
Wheel c y li n d e r s ize d i f f e r e n t on opposite sid es.
16.
Replace w ith c o r r e c t c y li n d e r s .
17.
Loose king pin or bushings.
17.
Replace king pins or bushings.
18.
Bad drum.
18.
R e finis h drums in p a ir s .
A d ju st.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -5 5
DIAGNOSIS—DRUM BRAKES
ONE WHEEL LOCKS
Probable Cause
Remedy
1. Gummy 1in in g .
1. Replace the l i n i n g s .
2. T ir e tread s l i c k .
2. Match up t i r e treads from side to sid e.
WET WEATHER: BRAKES GRAB OR W O N T HOLD
Probable Cause
Remedy
1. Linin gs too s e n s it iv e to water.
1. Replace the 1in in g s .
2. D i r t y brakes.
2. Clean.
3. Bent fla n g e p la te - opening.
3. S tra ig h te n .
4. Scored drums.
4. Grind or tu rn in pa irs,
BRAKES SQUEAK
Probable Cause
Rem edy
1. Flange p la te bent or shoes tw is te d .
1. Stra ig h te n or replace damaged p a rts .
2. M e t a l lic p a r t i c le s or dust imbedded in l i n i n g .
2. Sand the surfaces o f the l i n i n g s and drums. Remove a l l
p a r t i c le s o f metal t h a t may be found in the surface o f
the 1i ni ngs.
3. L inin g r i v e t s loose or l i n i n g not held t i g h t l y
a g ainst the shoe a t the ends.
3. Replace r i v e t s an d/or tig h t e n l i n i n g by r e - r i v e t i n g .
4. Drums not square or d i s t o r t e d .
5. Shoes scraping on fla n g e p la te ledges.
6. Weak or broken hold down s pring s .
Turn or grin d or replace drums.
5 . Apply Delco Brake Lube #5450032 (or e q u iv a le n t) to
ledges. Replace w ith new shoe and l i n i n g s , i f d i s t o r t e d .
Replace d e f e c t iv e p a rts .
7. Loose wheel be arings.
8. Loose fla n ge p la t e , anchor, drum wheel c y li n d e r .
9. Loose shoe 1 in k s .
10. Linin gs located wrong on shoes.
11. Brake drum s il e n c e r spring missing or too weak.
Tighten to proper s e t t i n g .
g
T ighten.
9
T ighten.
11.
In s ta ll lin in g s c o rre c tly .
I n s t a l l new s pring .
LIGHT DUTY TRUCK SERVICE MANUAL
5 -5 6 BRAKES
DIAGNOSIS—DRUM BRAKES
BRAKES CHATTER
Probable Cause
Remedy
1. I n c o rr e c t l i n i n g to drum cle arance.
1,. Readjust to recommended cle arances.
2. Loose fla n g e p la t e .
2,. Tighten s e cu re ly.
3. Grease, f l u i d , road dust on l i n i n g .
3.. Clean ou t d u st; repla ce grease and f l u i d soaked l i n i n g s .
4. Weak or broken r e t r a c t o r s p rin g .
4,. Replace.
5. Loose wheel bearings.
5,. Readjust.
6. Drums o u t-o f-ro u n d .
6,. Grind or tu rn drums in p a ir s .
7. Cocked or d i s t o r t e d shoes.
7,. S tra ig h te n or rep la c e.
8. Tapered or barrel-shaped drums.
8,. Grind or tu rn in p a ir s .
SHOE CLICK
Remedy
Probable Cause
1. Shoes l i f t o f f fla n g e p l a t e and snap back.
1. Change drums sid e to sid e or g rin d drums ( i n p a i r s ) .
2. Hold down springs weak.
2., Replace s pring s.
3. Shoe bent.
3., S tra ig h te n .
4. Grooves in fla n g e p l a t e pads.
4. Grind - lu b r i c a t e w ith Delco Brake Lube #5450032 (or
e q u iv a le n t).
SNAPPIN G NOISE IN FRONT END
Probable Cause
Remedy
1. Grooved fla n g e p la t e pads.
1 . Grind pads or repla ce fla n g e p l a t e .
2. Lack o f l u b r i c a t i o n on moving p a r ts .
2.. Lu brica te a l l rubbing po in ts w ith Delco Brake Lube
#5450032 (or e q u iv a le n t ) .
3. Loose drums or fla n g e p la t e s .
3.. Tig hte n.
4. Loose or worn f r o n t end p a rts .
4., Tighten or repla ce d e f e c t iv e p a r ts .
TH U M PIN G NOISE W HEN BRAKES ARE APPLIED
Probable Cause
Remedy
1. Too much clearance between shoes and anchors.
1 . A d ju st.
2. R e tra c to r springs unequal - weak.
2. Replace sp rin g s.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -5 7
DIAGNOSIS—DRUM BRAKES
G R IN D IN G NOISE
Probable Cause
Rem edy
1. Shoe h i t s drum.
1 . Switch drums or grin d drums.
2. Bent shoe web.
2. S tra ig h te n .
3. Foreign m aterial in l i n i n g .
3. Remove.
4. Rivets or shoe rubbing drum.
4. Reline - r e f i n i s h drums, i f scored.
5. L inin g charred.
5. Replace the 1in in g s .
6. Rough drum surface.
6. R e finis h drums.
DIAGNOSIS—DISC BRAKES
PULLS
Probable Cause
1. I n c o r r e c t t i r e pressures.
Rem edy
1 . I n f l a t e evenly on both sides to the recommended
pressures.
(See owner's manual.)
2. Front end out o f 1ine.
2. Check and a l i g n to m an ufac ture r's s p e c i f i c a t i o n s .
3. Unmatched t i r e s on same a x le .
3. T ires w ith approxim ately the same amount o f tread
should be used on the same a x le .
4. R e stric te d brake tubes or hoses.
4. Check f o r s o f t hoses and damaged l i n e s . Replace w ith
new hoses and new double -w alled stee l brake tu b in g .
5. M a lfu nc tio nin g c a l i p e r assembly.
5. Check f o r stuck or slu gg is h p is to n s .
6. D e fe ctiv e or damaged shoe &amp; l i n i n g (grease or brake
f l u i d on l i n i n g or bent shoe).
6. I n s t a l l new shoe and l i n i n g on complete a x le .
7. M alfu n ctio n in g rea r brakes.
7. Check f o r in o p e r a t iv e automatic a d ju s tin g
mechanism, d e f e c t iv e l i n i n g (grease o r brake f l u i d
on l i n i n g ) or d e f e c t iv e wheel c y l i n d e r s .
Repair
as necessary.
8. Loose suspension p a rts .
8. Check a l l suspension mountings.
9. Loose c a l ip e r s .
9. Check and torque a l l b o lt s to s p e c i f i c a t i o n s .
BRAKE ROUGHNESS OR CHATTER (PEDAL PULSATES)
Probable Cause
Rem edy
1. Excessive l a t e r i a l runout.
1 . Check per i n s t r u c t i o n s and resurfa ce the r o t o r , i f not
w ith in s p e c ific a tio n s .
2. P a ra lle lis m not w i t h i n s p e c if ic a t i o n s
2. Check per i n s t r u c t i o n s and res u rfa ce the r o t o r , i f not
w ith in s p e c ific a tio n s .
3. Wheel bearings not adjusted c o r r e c t l y
3. A d ju st wheel bearings to c o r r e c t s p e c i f i c a t i o n s .
LIGHT DUTY TRUCK SERVICE MANUAL
5 -5 8 BRAKES
DIAGNOSIS—DISC BRAKES
BRAKE ROUGHNESS, ETC. (C O N T .)
Probable Cause
Remedy
4. Rear drums o u t-o f- ro u n d .
4. Check runout and i f not w i t h i n s p e c i f i c a t i o n s , t u r n the
drums.
(Not over maximum o f .060 on the d ia m e te r.)
5. Shoe reversed (s te e l ag a in s t ir o n ) .
5. Replace r o t o r and shoe and l i n i n g .
EXCESSIVE PEDAL EFFORT
Probable Cause
Remedy
.
1. M alfu nctio nin g power brake.
1
2. P a r t ia l system f a i l u r e (dual master c y l i n d e r ) .
2. Check f r o n t and rea r brake system and r e p a i r i f
necessary. Also check brake warning l i g h t i f a f a i l e d
system is found and l i g h t did not f u n c t i o n .
Check power brake and r e p a i r i f necessary.
3. Excessively worn shoe and l i n i n g .
3. Check and replace in axle sets.
4. Pistons in c a lip e r s stuck or slu g g is h .
4. Remove c a lip e r s and r e b u i ld .
5. Fading brakes due to i n c o r r e c t l i n i n g .
5. Remove and repla ce w ith o r i g i n a l equipment.
EXCESSIVE PEDAL TRAVEL
Probable Cause
Remedy
.
1. P a r t ia l brake system f a i l u r e (w ith dual system master
c y lin d e rs ).
1
Check both f r o n t and rea r systems f o r a f a i l u r e and
r e p a i r . Also check warning l i g h t , i f v e h ic le is so
equipped.
I t should have in d ica te d a f a i l u r e .
2. I n s u f f i c i e n t f l u i d due to leak in system.
2. F i l l r e s e rv o ir s w ith GM Hydraulic Brake F lu id Supreme
No. 11 (or e q u i v a l e n t ) .
3. In c o rr e c t master c y li n d e r push rod adjustment.
3. Adjust c le v is where po ssib le .
4. A i r trapped in system.
4. Bleed system.
5. Rear brake not a d ju s tin g p ro p e rly .
5. Adjust re a r brakes and r e p a i r auto a d ju s te r s .
6. Bent shoe and l i n i n g .
6. Replace axle set o f shoe and l i n i n g .
D R A G G IN G BRAKES
(A very l i g h t drag is present in a l l disc brakes immediately a f t e r pedal is released)
Remedy
Probable Cause
.
1. Master c y li n d e r pisto ns not r e tu r n in g c o r r e c t l y .
1
With r e s e r v o ir cover o f f , check f o r f l u i d s p u r t a t bypass
holes as pedal is depressed. A d ju s t push rod, i f
necessary or r e b u ild master c y l i n d e r .
2. R e s tricte d brake tubes or hoses.
2. Check f o r s o f t hoses or damaged tubes and repla ce w ith
new hoses and new doub le-walled stee l brake tu b in g .
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -5 9
DIAGNOSIS—DISC BRAKES
DRAGGING BRAKES (CONT.)
Probable Cause
Remedy
3. I n c o rr e c t parking brake adjustment on rea r brakes.
3. Check and r e a d ju s t to c o r r e c t s p e c i f i c a t i o n s .
4. Metering valve i n s t a l l e d i n c o r r e c t l y .
4. Port marked &quot; i n l e t &quot; goes to master c y l i n d e r , Port
marked &quot; o u t l e t &quot; goes to dis c c a l i p e r s .
5. Check valve i n s t a l l e d in o u t l e t to f r o n t disc brakes.
5. Check o u t l e t hole and remove check va lve , i f l i n e is
connected to dis c brake c a l i p e r s .
G RABBING OR UNEVEN BRAKING A C TIO N
Probable Cause
1. A l l c o n d itio n s l i s t e d under &quot;PULLS&quot;.
Rem edy
1. See &quot;PULLS&quot;.
2. M alfu nctio n o f metering valve or p ro p o rtio n in g valve.
2. Replace and bleed system.
3. M alfu nctio n o f power brake u n i t .
3. Check o p era tion and r e p a i r , i f necessary.
4. Binding brake pedal mechanism.
4. Check and lu b r i c a t e w ith Delco Brake Lube #5450032
(or e q u iv a le n t) i f necessary.
5. Metering valve not hold in g o f f f r o n t brake a p p l ic a t io n .
5. Replace metering valve and bleed system. I f v e h ic le
is not equipped w ith metering va lv e , check o th er
causes.
REAR DRUM BRAKES SKIDDING PREMATURELY UNDER HARD BRAKE APPLICATION
Probable Cause
1. P rop o rtio n in g valve not c o n t r o l l i n g rea r l i n e pressure
to prevent rea r wheel lockup on hard brake a p p lic a t io n s
Remedy
1. Replace p r o p o r tio n in g valve and bleed system.
If
v e h ic le is not equipped w ith p r o p o r tio n in g v a lv e ,
check o th e r causes l i s t e d under &quot;PULLS&quot; or &quot;GRABBING
OR UNEVEN BRAKING ACTION&quot;.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -6 0 BRAKES
POWER BRAKES
INDEX
General Description..........................................................................
Theory of Operation.........................................................................
Maintenance and Adjustments......................................................
Inspection............................................................................................
Lubrication..........................................................................................
Bleeding...............................................................................................
Air Cleaner Service.........................................................................
Component Part Replacement.......................................................
Power Brake U nit............................................................................
Diagnosis...............................................................................................
5-60
5-60
5-66
5-66
5-66
5-66
5-66
5-66
5-66
5-67
GENERAL DESCRIPTION
The Power brake Unit is a self-contained hydraulic and
vacuum unit, utilizing manifold vacuum and atmospheric
pressure for its power.
This unit permits the use of a low brake pedal as well as
less pedal effort than is required with the conventional
(nonpower) hydraulic brake system. The unit is mounted
on the engine side of the dash panel and directly
connected to the brake pedal.
THEORY OF OPERATION
A power brake is used with the brake system to reduce
the braking effort required by the driver. A combined
vacuum and hydraulic unit, which utilizes engine
manifold vacuum and atmospheric pressure, is used to
provide power assisted application of vehicle brakes.
The unit is used in conjunction with a conventional
brake system. From the master cylinder connection
outward to the wheel units, there is no other change in
the brake system.
In addition to the master cylinder connections, the unit
requires a vacuum connection to the engine intake
manifold (through a vacuum check valve) and a
mechanical connection to the brake pedal. The unit is
self-contained.
The vacuum power unit contains the power piston
assembly, which houses the control valve and reaction
mechanism, and the power piston return spring. The
control valve is composed of the air valve (valve
plunger), the floating control valve assembly, and the
push rod. The reaction mechanism consists of a
hydraulic piston reaction plate and a series of levers. An
air filter, air silencer, and filter retainer are assembled
around the valve operating rod filling the cavity inside
the hub of the power piston. The push rod or valve
operating rod, which operates the air valve, projects out
of the end of the power unit housing through a rubber
dust guard. A vacuum check valve assembly is mounted
in the front housing assembly for connection to the
vacuum source.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
RESERVOIR COVER
5-61
FRONT SHELL
REAR SHELL
POWER PISTON DIAPHRAGM
FLUID RESERVOIRS
REACTION RETAINER
POWER PISTON INSERT
REACTION LEVER
REACTION SPRING
FLOATING CONTROL VALVE
PUSH ROD
AIR FILTER
FLOATING PISTON STOP BOLT
FLOATING PISTON ASSEMBLY
SILENCER
AIR VALVE
REACTION PLATE
POWER PISTON RETURN SPRING
MASTER CYLINDER PUSH ROD
COMPENSATING PORT
SUPPORT PLATE
AIR FILTER
PRIMARY PISTON ASSEMBLY
Fig. 86--Typical Power Unit
RELEASED (Figs. 86 and 87)
At the released position the air valve is seated on the
floating control valve. Air at atmospheric pressure, which
enters through the filter element in the tube extension of
the power piston, is shut off at the air valve. The floating
control valve is held away from the valve seat in the
power piston insert. Vacuum is present in the space on
Released
both sides of the power piston. Any air in the system is
drawn through a small passage in the power piston, over
the valve seat in the power piston insert, and then
through a passage in the power piston insert. From here
it travels through a hole in the power piston support
plate into the space in front of the power piston. It is
then drawn through the check valve and into the engine
intake manifold.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -6 2 BRAKES
Fig. 8 7 -Typical Circuit - Released
In this position there is vacuum on both sides of the
power piston, and the power piston is held against the
rear of the housing by the power piston return spring. At
rest, the hydraulic reaction plate is held against the
reaction retainer. The air valve spring holds the reaction
levers against the hydraulic reaction plate and also holds
the air valve against its stop in the tube of the power
piston. The floating control valve assembly is held
against the air valve seat by the floating control valve
spring.
With the power brake at released position, the master
cylinder primary seals on both the rear (primary) piston
and the floating (secondary) piston are back past the two
compensating ports in the bore.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -6 3
VACUUM
REACTION
PLATE
FLOATING
CONTROL
VALVE
AIR VALVE
UNSEATED
AIR VALVE
REACTION
LEVERS
ATMOSPHERIC
PRESSURE
Fig. 88-Typical Power Unit - Applying
APPLYING (Figs. 88 and 89)
As the pedal is depressed, the valve operating rod (push
rod) carries the air valve away from the floating control
valve. The floating control valve will follow until it is in
contact with the raised seat in the power piston insert.
When this occurs, vacuum is shut off to the rear of the
power piston, and air under atmospheric pressure enters
through the air filter and travels past the seat of the air
valve and through a passage into the housing at the rear
of the power piston. Since there is still vacuum on the
front side of the power piston, the atmospheric air
pressure at the rear of the piston will force the power
piston to travel forward.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -6 4 BRAKES
Fig. 8 9 -Typical Circuit - Applying
As the power piston travels forward, the master cylinder
piston rod carries the master cylinder primary piston
further into the bore of the master cylinder. The force
on the master cylinder primary piston spring forces the
secondary piston to move forward. As the primary seal,
on both the master cylinder primary and the secondary
pistons pass the compensating ports in the bore,
hydraulic pressure will build up in the lines to the front
and rear brakes. As the pressure builds up on the end of
the master cylinder piston, the hydraulic reaction plate is
moved off its seat on the power piston and presses
against the reaction levers. The levers, in turn, swing
about their pivots and bear against the end of the air
valve operating rod assembly. In this manner approx&shy;
imately 30% of the load on the hydraulic master cylinder
piston is transferred back through the reaction system to
the brake pedal. This gives the operator a feel, which is
proportional to the degree of brake application.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -6 5
VACUUM
REACTION
PLATE
FLOATING
CONTROL
VALVE
AIR VALVE
SEATED
AIR VALVE
REACTION
LEVERS
ATMOSPHERIC
PRESSURE
Fig. 90--Typical Power Unit - Holding
HOLDING (Figs. 90 and 91)
When the desired pedal pressure is reached, the power
piston moves forward until the floating control valve,
which is still seated on the power piston, again seats on
the air valve. The power piston will now remain
stationary, until either pressure is applied or released at
the brake pedal. As the pressure at the pedal is released,
the air valve spring forces the air valve back to its stop
on the power piston. As it returns, the air valve pushes
the floating control valve off its seat on the power piston
insert. The air valve seating on the floating control valve
has shut off the outside air source. When it lifts the
floating control valve from its seat on the power piston
insert, it opens the space at the rear of the power piston
to the vacuum source.
Since both sides of the power piston are now under
vacuum, the power piston return spring will return the
piston to its released position against the rear housing.
As the power piston is returned, the master cylinder
primary and secondary pistons move back, and the fluid
from the wheel cylinders flows back into the master
cylinder. If the brake pedal is released quickly, the
master cylinder primary and secondary pistons immedi&shy;
ately return to the released position. If the fluid in the
lines cannot return as quickly as the pistons, this is
compensated for by the flow of fluid from the space
between the primary and secondary seals through the
compensating holes in the pistons. The excess fluid in the
system can flow back to the fluid reservoirs through the
small compensating ports in the master cylinder bore.
LIGHT DUTY TRUCK SERVICE MANUAL
5 66 BRAKES
Fig. 91--Typical Circuit • Holding
VACUUM FAILURE
In case of vacuum source interruption, the brake unit
operates in the following manner:
As the pedal is pushed down, the end of the air valve
contacts the reaction levers and pushes, in turn, against
the hydraulic reaction plate. Since the hydraulic reaction
plate is fastened to the master cylinder piston rod, it
forces the piston rod against the master cylinder primary
piston, which builds up the hydraulic line pressure. With
this condition you have, in effect, a standard brake unit.
M A IN TEN A N C E A N D ADJUSTMENTS
INSPECTIONS
1. Check vacuum line and vacuum line connections as
well as vacuum check valve in front housing of
power unit for possible vacuum loss.
2. Inspect all hydraulic lines and connections at the
wheel cylinders and master cylinder for possible
hydraulic leaks.
3. Check brake assemblies for scored drums, grease or
brake fluid on linings, worn or glazed linings, and
make necessary adjustments.
4. Check brake fluid level in the hydraulic reservoirs.
The reservoirs should be filled to the levels shown
in Figure 31.
5. Check for loose mounting bolts at master cylinder
and at power section.
6 . Check air cleaner filter in power piston extension
and replace filter if necessary.
7. Check brake pedal for binding and misalignment
between pedal and push rod.
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
LUBRICATION
The power brake unit is lubricated at assembly and
needs no further lubrication other than maintaining
normal reservoir fluid level. The reservoir should be
filled as described in this section.
BLEEDING
The power system may be bled manually or with a
pressure bleeder as outlined in this section. Use only GM
Supreme 11 Brake Fluid or equivalent. Do not use the
power assist while bleeding. The engine should not be
5 -6 7
running and the vacuum reserve should be reduced to
zero by applying the brake several times before starting
the bleeding procedure.
AIR CLEANER SERVICE
Servicing of the air cleaner is recommended and the
element replaced when restriction becomes severe
enough to affect power brake response. At any other
time, if cleaning of the filter is felt necessary, it should
be shaken free of dirt or washed in soap and water and
thoroughly dried.
C O M P O N E N T PART REPLACEMENT
POWER BRAKE UNIT
Removal
1. Remove all dirt from the exterior of the master
cylinder. Disconnect the brake lines from the two
master cylinder hydraulic outlets. Cover brake line
fittings to prevent dust and dirt from entering brake
lines.
2. Disconnect the vacuum hose from the vacuum
check valve on the front housing of the power head.
Plug vacuum hose to prevent dust and dirt from
entering hose.
3. Disconnect the power brake push rod from the
brake pedal.
4. Remove the four nuts (inside vehicle) from the
mounting studs which hold the power brake to the
dash panel.
5. Carry the power brake to a clean work area and
clean the exterior of the power brake prior to
disassembly (see the applicable portion of the
&quot;Overhaul&quot; manual for disassembly at the power
unit).
Installation
1. Mount power brake assembly to dash.
CAUTIO N: See &quot;Caution&quot; on Page 1 of this
section.
2. Connect power brake push rod to brake pedal.
3. Connect vacuum hose to vacuum check valve.
4. Connect brake lines to master cylinder outlets.
CAUTIO N: See &quot; Caution&quot; on Page 1 of this
section.
5. Bleed brakes as necessary and fill fluid reservoirs to
within 1/4&quot; of top of the reservoirs.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -6 8 BRAKES
DIAGNOSIS
NOTE The same types o f brake troub le s are encountered
w ith power brakes as w ith standard brakes. Before check&shy;
ing the power brake system f o r source o f t r o u b le , r e f e r
to tro u b le diagnosis o f standard h y d ra u lic brakes in t h is
manual. A f t e r these p o ssib le causes have been e lim in a te d ,
check f o r cause as o u t lin e d below.
BRAKE SYSTEM LOSES FLUID
Probable Cause
Remedy
1. External le ak: 1eakin g-pipe connections, hose, wheel
c y li n d e r s , stop l i g h t s w itc h , master c y li n d e r head nut,
e tc.
1. Clean p a rts .
Tig hte n.
Replace d e f e c t iv e parts,
2. In te rn a l le aks: past secondary seals in to power u n i t .
Check vacuum hose f o r f l u i d .
2. Rebuild master c y l i n d e r .
NOTE: Make the f o llo w in g t e s t before checking hard pedal
f o r the cause. With the, engine stopped, depress the brake
pedal several times to e lim in a te a l l vacuum from the system.
Apply the brakes, and w h ile holding the f o o t pressure on the
brake pedal, s t a r t the engine. I f the u n i t is operating
c o r r e c t l y , the brake pedal w i l l move forward when the engine
vacuum power is added to the pedal pressure.
I f th is te s t
shows t h a t the power u n i t is not o p e ra tin g , the t r o u b le may
be one o f the f o ll o w i n g :
N O B O O S T -H A R D PEDAL
Probable Cause
1
.
Bent, broken, obstru cted tube.
Collapsed hose.
Remedy
1
.
Replace d e f e c t iv e p a r ts .
2. Stuck check valve.
2. Replace valve.
3. A i r i n l e t blocked.
3. Replace f i l t e r .
4. A i r valve stuck.
4. Disassemble u n i t - clean - replace d e f e c t iv e
5. F aulty diaphragm.
5. Replace diaphragm.
6. F aulty p is to n s e a l .
7. Leaks i n t e r n a l l y .
Open passages.
6. Replace s e a l .
7. Rebuild as o u t lin e d in the &quot;Overhaul&quot; Manual.
Tighten b o l t s .
LIGHT DUTY TRUCK SERVICE MANUAL
BRAKES
5 -6 9
DIAGNOSIS—POWER HYDRAULIC BRAKES
SLOW BRAKE PEDAL RETURN
Probable Cause
Remedy
1. Excessive seal f r i c t i o n in power u n i t .
1.
Overhaul u n i t as o u t lin e d in the &quot;Overhaul&quot; Manual.
2. F aulty valve a c t io n .
2.
Overhaul u n i t .
3. Broken r e tu r n s p rin g .
3.
Replace s p rin g .
BRAKES GRABBY
Probable Cause
Remedy
1. Broken valve s p rin g .
1. Overhaul u n i t .
2. S t ic k in g vacuum valve.
2. Clean and lu b r i c a t e w ith Delco S ilic o n e Lube #5459912
(or e q u i v a l e n t ) .
3. Reaction diaphragm leakage.
3. Overhaul u n i t .
BRAKES CHATTER: PEDAL VIBRATES (BELLOWS TYPE)
Probable Cause
Remedy
1. Brake pedal fre e play not adjusted p ro p e rly .
1. A djust brake pedal f r e e play.
BRAKE PEDAL CHATTER (BELLOWS TYPE)
Probable Cause
Remedy
1. Power brake t r i g g e r is out o f adjustment or bent.
1. Replace t r i g g e r and a d ju s t li n k a g e .
2. Master c y li n d e r push rod is improperly adju ste d.
2. Adjust push rod.
3. Power brake t r i g g e r rubber c o l l a r is missing or
damaged.
3. Replace w ith new c o l l a r .
4. Binding in s id e power u n i t .
4. Overhaul u n i t .
NOTE: I f tr o u b le is determined as being caused by the power
bo oster, r e f e r to the a p p lic a b le Service or Overhaul Manual
f o r service procedures.
LIGHT DUTY TRUCK SERVICE MANUAL
5 -7 0 BRAKES
SPECIAL TOOLS
GUU
1.
2.
3.
4.
J-2185 Flaring Tool
J-8000 Tubing Cutter
J-8049 or J-22348 Spring Remover
J-21177 Drum/Shoe Gage
5.
6.
7.
8.
J-21472
J-22904
J-23518
J-23709
Bleeder Wrench
Dust Boot Installer
Bleeder Adapter
Combination Valve Pin Retainer
Fig. 9 2 -Special Tools
LIGHT DUTY TRUCK SERVICE MANUAL
SECTION 6
ENGINE
CONTENTS OF THIS SECTION
Engine Tune-Up................................................................... 6-1
Theory of Operation.......................................................... 6-14
Engine Mechanical (In Line)......................................... 6-19
Engine Mechanical (V8 ).................................................... 6-44
Diagnosis................................................................................. 6-68
Special Tools......................................................................... 6-73
ENGINE TUNE-UP
INDEX
General Description................................................ ...........
Mechanical Checks and Adjustments............... ...........
Spark Plug Removal............................................ ..........
Test Compression................................................... ...........
Service and Install Spark Plugs....................... ..........
Service Ignition System....................................... ...........
Service Battery and Battery Cables................ ...........
Service Delcotron and Regulator..................... ...........
Service Belts............................................................ ..........
Service Manifold Heat Valve............................ ..........
Tighten Manifold................................................... ..........
Service Fuel Lines and Fuel Filter................ ..........
Service Cooling System....................................... ...........
Service Crankcase Ventilation......................................
Service Air Injection Reactor System............. ..........
6-1
6-1
6-1
6-2
6-2
6-2
6-3
6-4
6-5
6-5
6-5
6-5
6-5
6-6
6-6
Choke Adjustment.......................................................... ...
Instrument Check-Out..................................................... ...
Instrument Hook-Up..................................................... ...
Check and Adjust Dwell.............................................. ...
Check Dwell Variation................................................. ...
Check and Adjust Timing........................................ ...
Adjust Idle Speed.......................................................... ...
Additional Checks and Adjustments......................... ...
Cylinder Balance Test................................................... ...
Battery................................................................................ ...
Ignition.............................................................................. ...
Carburetor......................................................................... ...
Fuel Pum p........................................................................ ...
Cooling System........................................................ ....... ...
Cylinder Head Torque and Valve Adjustment ...
6-7
6-8
6-8
6-8
6-8
6-8
6-9
6-11
6-11
6-11
6-11
6-13
6-13
6-13
6-13
GENERAL DESCRIPTION
The engine tune-up is important to the modern
automotive engine with its vastly improved power and
performance. Emission system requirements, interrelated
system functions, improved electrical systems and other
advances in design, make today’s engines more sensitive
and have a decided effect on power, performance and
fuel consumption.
It is seldom advisable to attempt a tune up by correction
of one or two items only. Time will normally be saved
and more lasting results assured if the technician will
follow a definite and thorough procedure of analysis and
correction of all items affecting power, performance and
economy.
The tune-up will be performed in two parts. The first
part will consist of mechanical checks and adjustments;
the second part will consist of an instrument checkout
that can be performed with any one of the units of
service equipment available for this purpose. Always
follow the instructions provided by the manufacturer of
the particular equipment to be used.
Additional checks and adjustments are included in the
latter part of this section for use as required. Many of
these operations can be used to isolate and correct
trouble located during the tune-up. Where conditions are
uncovered requiring major corrective action, refer to the
appropriate section of this manual or the Overhaul Manual
for detailed service information.
Typical illustrations and procedures are used except
where specific illustrations or procedures are necessary to
clarify the operation. Illustrations showing bench
operations are used for clarification, however, all
operations can be performed on the vehicle.
MECHANICAL CHECKS A N D ADJUSTMENTS
SPARK PLUG REMOVAL
Remove any foreign matter from around spark plugs by
blowing out with compressed air, then disconnect wires
and remove plugs. To disconnect wire at spark plug,
grasp the boot portion of the wire and apply only
LIGHT DUTY TRUCK SERVICE MANUAL
6-2 ENGINE
enough force to remove the boot. Do not pull on plug
wire.
TEST COMPRESSION (FIG. 1)
The compression check is important because an engine
with low or uneven compression cannot be tuned
successfully. It is essential that improper compression be
corrected before proceeding with the engine tune up.
1. Remove air cleaner and block throttle and choke in
wide open position.
2. Hook up starter remote control cable and insert
compression gauge firmly in spark plug port.
CAUTION: Whenever the engine is cranked
remotely at the starter, with a special jumper
cable or other means, the distributor primary
lead must be disconnected from the negative
post on the coil.
3. Crank engine through at least four compression
strokes to obtain highest possible reading.
4. Check and record compression of each cylinder.
5. If one or more cylinders read low or uneven, inject
about a tablespoon of engine oil on top of pistons
in low reading cylinders (through spark plug port).
Crank engine several times and recheck
compression.
• If compression comes up but does not necessarily
reach normal, rings are worn.
• If compression does not improve, valves are
burned, sticking or not seating properly.
• If two adjacent cylinders indicate low compres&shy;
sion and injecting oil does not increase
compression, the cause may be a head gasket
leak between the cylinders. Engine coolant and/
or oil in cylinders could result from this defect.
NOTE: If a weak cylinder cannot be located
with the compression check, see “Cylinder
Balance Test” under “Additional Checks and
Adjustments” in this section.
SERVICE AND INSTALL SPARK
PLUGS (FIG. 2 )
1. Inspect each plug individually for badly worn
electrodes, glazed, broken or blistered porcelains
and replace plugs where necessary.
2. Clean serviceable spark plugs thoroughly, using an
abrasive-type cleaner such as sand blast. File the
center electrode flat.
3. Inspect each spark plug for make and heat range.
All plugs must be of the same make and number.
4. Adjust spark plug gaps to specifications using a
round feeler gauge.
CAUTIO N: Never bend the center electrode to
adjust gap. Always adjust by bending ground
or side electrode.
5. If available, test plugs with a spark plug tester.
6 . Inspect spark plug hole threads and clean before
installing plugs. Corrosion deposits can be removed
with a 14 m m .x 1.25 SAE spark plug tap (available
through local jobbers) or by using a small wire
brush in an electric drill. (Use grease on tap to
catch chips.)
CAUTIO N: Use extreme care when using tap to
prevent cross threading. Also crank engine
several times to blow out any material
dislodged during cleaning operation.
7. Install spark plugs and torque to specifications.
NOTE: The following are some of the
greatest causes of unsatisfactory spark plug
performance.
• Installation of plugs with insufficient torque to
fully seat.
• Installation of the plugs using excessive torque
which changes gap settings.
• Installation of plugs on dirty seat.
• Installation of plugs to corroded spark plug hole
threads.
8 . Connect spark plug wiring.
SERVICE IG N ITIO N SYSTEM
Fig. 1—Checking Compression
1. Remove distributor cap, clean cap and inspect for
cracks, carbon tracks and burned or corroded
terminals. Replace cap where necessary (fig. 3).
2. Clean rotor and inspect for damage or deteriora&shy;
tion. Replace rotor where necessary.
3. Replace brittle, oil soaked or damaged spark plug
wires. Install all wires to proper spark plug. Proper
positioning of spark plug wires in supports is
important to prevent cross-firing.
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
Fig. 2—Spark Plug Detail
4. Tighten all ignition system connections.
5. Replace or repair any wires that are frayed, loose
or damaged.
Distributor (Figs. 4 or 5)
1. Check the distributor centrifugal advance mecha&shy;
nism by turning the distributor rotor in a clockwise
direction as far as possible, then releasing the rotor
to see if the springs return it to their retarded
position. If the rotor does not return readily, the
distributor must be disassembled and the cause of
the trouble corrected.
2. Check to see that the vacuum control operates
freely by turning the movable breaker plate
counterclockwise to see if the spring returns to its
retarded position. Any stiffness in the operation of
the vacuum control will affect the ignition timing.
Correct any interference or binding condition
noted.
3. Examine distributor points and clean or replace if
necessary.
• Contact points with an overall gray color and
only slight roughness or pitting need not be
replaced.
• Dirty points should be cleaned with a clean point
file.
Use only a few strokes of a clean, fine-cut contact
file. The file should not be used on other metals and
should not be allowed to become greasy or dirty.
Never use emery cloth or sandpaper to clean contact
points since particles will embed and cause arcing
and rapid burning of points. Do not attempt to
6-3
remove all roughness nor dress the point surfaces
down smooth. Merely remove scale or dirt.
• Clean cam lobe with cleaning solvent and rotate
cam lubricator wick 180&deg;.
NOTE: Where prematurely burned or badly
pitted points are encountered, the ignition
system and engine should be checked to
determine the cause of trouble so that it can
be eliminated. Unless the condition causing
point burning or pitting is corrected, new
points will provide no better service than the
old points. Refer to Section 6 Y for an
analysis of point burning or pitting.
• Check point alignment (fig. 6 ) then, adjust
distributor contact point gap to .019&quot; (new
points) or .016&quot; (used points). Breaker arm
rubbing block must be on high point of lobe
during adjustment.
NOTE: If contact points have been in service,
they should be cleaned with a point file
before adjusting with a feeler gauge.
• Check distributor point spring tension (contact
point pressure) with a spring gauge hooked to
breaker lever at the contact and pull exerted at
90 degrees to the breaker lever. The points
should be closed (cam follower between lobes)
and the reading taken just as the points separate.
If not within limits, replace.
Excessive point pressure will cause excessive wear on
the points, cam and rubbing block. Weak point
pressure permits bouncing or clattering, resulting in
arcing and burning of the points and an ignition
miss at high speed.
4. Install rotor and distributor cap. Press all wires
firmly into cap towers.
SERVICE BATTERY AND BATTERY
CABLES
1. Measure the specific gravity of the electrolyte in
each cell (fig. 7). If it is below 1.230 (corrected to
80&deg;F.) recharge with a slow rate charger, or if
desired, further check battery.
2. Connect a voltmeter across the battery terminals
and measure the terminal voltage of the battery
during cranking (disconnect the coil primary lead at
the negative terminal during this check to prevent
engine from firing). If the terminal voltage is less
than 9.0 volts at room temperature, approximately
80&deg; &plusmn; 20&deg;F., the battery should be further checked.
See Section 6 Y for further tests.
3. Inspect for signs of corrosion on battery, cables and
surrounding area, loose or broken carriers, cracked
or bulged cases, dirt and acid, electrolyte leakage
and low electrolyte level. Fill cells to proper level
With colorless, odorless, drinking water.
The top of the battery should be clean and the
LIGHT DUTY TRUCK SERVICE MANUAL
6 -4 ENGINE
CARBON L
PATH
CRACK
CARBON
PATH
ERODED
TOWER
INSPECTION OF DISTRIBUTOR
CAP TOWERS
CLEANING &amp; INSPECTION OF
OUTSIDE OF DISTRIBUTOR CAP
ROTOR TIP
CORRODED
BURNED OR
ERODED
INSERT
TERMINALS/
CLEANING &amp; INSPECTION OF
INSIDE OF DISTRIBUTOR CAP
REPLACING DISTRIBUTOR
CAP
INSUFFICIENT
ROTOR CONTACT
SPRING
TENSION
ROTOR INSPECTION
BLOWING OUT INSIDE OF DISTRIBUTOR
CAP &amp; INSPECTION OF INSERT
_____________ TERMINALS_____________
CLEANING TOWER INSERT
CLEANING IGNITION
COIL
INSPECTION OF CARBON
ROTOR BUTTON
Fig. 3—Cleaning and Inspecting Distributor Cap, Rotor and Coil
CAM LUBRICATOR
CONTACT SET
ATTACHING
SCREW
QUICK
DISCONNECT
TERMINAL
BREAKER PLATE
ATTACHING SCREWS
Fig. 4-D istributor (In Line)
battery hold-down bolts properly tightened. Particu&shy;
lar care should be taken to see that the top of the
battery is kept clean of acid film and dirt. When
cleaning batteries, wash first with a dilute ammonia
or soda solution to neutralize any acid present and
then flush off with clean water. Keep vent plugs tight
so that the neutralizing solution does not enter the
cell. The hold down bolts should be kept tight
enough to prevent the battery from shaking around
in its holder, but they should not be tightened to the
point where the battery case will be placed under a
severe strain.
To insure good contact, the battery cables should be
tight on the battery. If the battery cable terminals
are corroded, the cables should be cleaned
separately with a soda solution and wire brush.
If the battery has remained undercharged, check for
loose or defective fan belt, defective Delcotron, high
resistance in the charging circuit, oxidized regulator
contact points, or a low voltage setting.
If the battery has been using too much water, the
voltage output is too high.
SERVICE DELCOTRON AND
REGULATOR
yê Delcotron and regulator tests during tune up consist
of the above battery tests; the condition of the battery
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
LATERAL
MISALIGNMENT
WEIGHT
ASSEMBLY
6-5
PROPER
LATERAL ALIGNMENT
ROTOR
II'
If
R.F.I. SHIELD
Li
CIRCUIT BREAKER
PLATE ASSEMBLY
ACCESS PASSAGE
FOR ENGINE OIL
FUMES
DISTRIBUTOR
HOUSING
GEAR
SHAFT
BUSHING
'&quot;J
CORRECT LATERAL MISALIGNMENT BY
BENDING FIXED CONTACT SUPPORT
NEVER BEND BREAKER LEVER
PERMANENT
LUBRICATION
RESERVOIR
VACUUM
ASSEMBLY
-'1
.11
Fig. 6—Point Alignment
DO NOT SUCK
IN TOO MUCH
ELECTROLYTE
HOLD
TUBE
VERTICAL
FLOAT MUST----BE
Fig. 5—Distributor (V8)
will indicate the need for further tests and adjustments
as outlined in Section 6 Y.
SERVICE BELTS (FIG. 8 )
Inspect belt condition.
Check and adjust if necessary for correct tension of belt,
as follows:
• Using a strand tension gauge, check the belt tension.
• If belt is below the minimum, adjust until the
specified tension, is reached. (See Tune Up Chart in
Specification section.)
SERVICE MANIFOLD HEAT
VALVE (FIG. 9 or 1 0 )
Check manifold heat control valve for freedom of
operation. If shaft is sticking, free it up with GM
Manifold Heat Control Solvent or its equivalent.
NOTE: Tap shaft end to end to help free it
up.
TIGHTEN MANIFOLD
Tighten intake manifold bolts to specifications in the
sequence outlined on Torque Sequence Chart located at
end of Engine Mechanical section. A slight leak at the
intake manifold destroys engine performance and
economy.
TAKE READING
AT EYE LEVEL
Fig. 7—Testing Specific Gravity of Battery
SERVICE FUEL LINES AND FUEL
FILTER
1. Inspect fuel lines for kinks, bends or leaks and
correct any defects found. Refer to Section 8 for the
correct fabrication and replacement procedures for
fuel lines.
2. Inspect filter and replace if plugged.
NOTE: If a complaint of poor high speed
performance exists on the vehicle, fuel pump
tests described in Section 6 M should be
performed.
SERVICE COOLING SYSTEM
1. Inspect cooling system for leaks, weak hoses, loose
hose clamps and correct coolant level, and service
as required.
NOTE: A cooling system pressure test, as
described in “Additional Checks and Adjust&shy;
ments” in this section, may be performed to
LIGHT DUTY TRUCK SERVICE MANUAL
6 -6 ENGINE
Fig. 9—Manifold Heat Control Valve (L6)
Fig. 8—Checking Fan Belt Tension
detect internal or external leaks within the
cooling system.
SERVICE CRANKCASE
VENTILATION (FIG. 1 1 )
All engines have a “Closed Positive” ventilation system
utilizing manifold vacuum to draw fumes and contami&shy;
nating vapors into the combustion chamber where they
are burned. Since it affects every part of the engine,
crankcase ventilation is an important function and
should be understood and serviced properly.
In a “Closed Positive” ventilation system, air is drawn
through the engine crankcase (through a regulating
valve) (fig. 12) into the manifold, drawing crankcase
vapors and fumes with it to be burned. The “Closed
Positive” ventilation system draws clean air from the
carburetor air cleaner and has a nonvented oil filler cap.
1. Ventilation valve should be replaced at intervals
specified in Section 0.
2. Inspect for deteriorated or plugged hoses.
3. Inspect all hose connections.
4. Remove flame arrestor and wash in solvent, then
dry with compressed air.
5. Inspect ventilation filter (fig. 13) and replace if
necessary.
SERVICE AIR INJECTION
REACTOR SYSTEM
Inspect air injection reactor system for evidence of leaks,
deteriorated hoses, cracked air manifolds or tubes and
loose hose clamps. Inspect air injection pump belt
Fig. 10—Manifold Heat Control Valve (Typical V8)
condition and tension. Make all necessary repairs as
outlined in “Section 6 T ” .
Because of the relationship between “Engine Tune U p”
and “Unburned Exhaust Gases”, the condition of Engine
Tune Up should be checked whenever the Air Injection
Reactor System seems to be malfunctioning. Particular
care should be taken in checking items that affect fuelair ration such as the crankcase ventilation system, the
carburetor and the carburetor air cleaner. Carburetors
and distributors for engines with the Air Injection
Reactor System and Controlled Combustion System are
designed, particularly, for these engines; therefore, they
must not be interchanged with or replaced by a
LIGHT DUTY TRUCK SERVICE MANUAL
ENGINE 6-7
carburetor or distributor designed for different
applications.
CHOKE ADJUSTMENT
Inspect choke valve, choke rod, choke coil and housing
for proper alignment, bends and binding — make
necessary corrections to assure proper choke operation;
then adjust choke as outlined in Section 6 M.
Fig. 11—Crankcase Ventilation Systems
LIGHT DUTY TRUCK SERVICE MANUAL
6-8 ENGINE
C R A N K C A S E V E N T IL A T IO N FILTER
Fig. 13—Crankcase Ventilation Filter
INSTRUMENT CHECK-OUT
INSTRUMENT HOOK-UP
Connect vacuum gauge, dwell meter, tachometer and
timing light as recommended by the manufacturer of the
equipment being used.
CHECK AND ADJUST DWELL
1. Start engine then check ignition dwell.
2. If dwell is not within specifications, adjust dwell as
follows:
V8 Engine
• With engine running at idle, raise the
adjustment
screw window and insert an Allen
wrench in the
socket of the adjusting screw (fig. 14).
• Turn the adjusting screw as required until the
specified dwell
reading is obtained.
•Close access cover fully to prevent the entry of dirt
into the distributor.
In Line Engines
• Remove distributor cap and recheck
point setting.
If dwell is still not within specifications
check the
distributor as outlined in Section 6Y.
CHECK DWELL VARIATION
Slowly accelerate engine to 1750 rpm
reading. Return engine to idle and note
dwell variation exceeds specifications,
distributor shaft, worn distributor shaft
breaker plate.
and note dwell
dwell reading. If
check for worn
bushing or loose
CHECK AND ADJUST IG NITIO N
TIM ING (FIG. 1 5 )
1. Disconnect the distributor spark advance hose and
plug the vacuum source opening.
2. Start engine and run at idle speed. (See tune up
chart in Specification section.)
3. Aim timing light at timing tab.
NOTE: The markings on the tabs are in 2&deg;
increments (the greatest number of markings
on the “ Before” side of the “O ” ). The “O”
marking is TDC and all BTDC settings fall
on the “Before” (advance) side of “O ” .
4. Adjust the timing by loosening the distributor
clamp and rotating the distributor body as required,
then tighten the clamp and recheck timing.
5. Stop engine and remove timing light and reconnect
the spark advance hose.
LIGHT DUTY TRUCK SERVICE MANUAL
ENGINE 6-9
W INDOW
&quot;H E X ” TYPE
W RENCH
SCREW
Fig. 14—Setting Point Dwell (Typical V8)
ADJUST IDLE SPEED (FIG. 16)
Emission system requirements necessitate the division of
the Series 10-30 trucks into two groups as follows:
a. Light Duty Emission Vehicles - Includes all 10
Series; C-K20 Suburban Models; All G20 Series
and G30 Passenger Models.
b. Heavy Duty Emission Vehicles - Includes all C-KP20 Series (Except C-K20 Suburban Models); all
C-P30 Series and all G30 Series (Except Passenger
Models).
NOTE: Idle speed will increase as new
engines loosen up during the first few
hundred miles of operation. Idle speed should
be reset during tune-up as specified in the
following procedures.
With engine running at operating temperature, air
cleaner installed, choke valve in fully open position, air
conditioning “off”, parking brake on and drive wheels
blocked - adjust idle speed as follows (See “Tune-up”
Decal Figure 17.):
NOTE: All carburetors are equipped with
idle mixture limiter caps (fig. 16), the idle
mixture is preset and “locked in” by these
caps - no attempt should be made to adjust
mixture. Do not remove mixture screw caps.
•
250 Cu. In. (Single-Barrel Carburetor)
On 250 cu. in. Light-Duty vehicles, disconnect “Fuel
Tank” line from Evaporation Emission vapor canister.
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
Adjust Idle Stop Solenoid (turn solenoid body, using hex
nut) to obtain:
700 rpm on all Heavy-Duty Vehicles and all LightDuty vehicles equipped with manual transmission
(in neutral).
Fig. 15—Ignition Timing Marks
600 rpm on Light-Duty vehicles equipped with
automatic transmissions (in “Park”).
NOTE: Light-Duty vehicles are equipped
with the carburetor mounted CEC solenoid
(fig. 16). DO NOT ADJUST THE CEC
SOLENOID SCREW.
CAUTIO N: If the CEC solenoid screw (fig. 16)
is used to set engine idle or if the solenoid is
adjusted out of limits as specified in Section
6M, a decrease in engine braking may result.
Place transmission in “park” or netural and adjust
carburetor fast idle speed to obtain 1800 rpm with cam
follower on top step of cam.
Reconnect “Fuel Tank” line to vapor canister and
reconnect distributor spark advance hose.
•
292 Cu. In. (Single-Barrel Carburetor)
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
Adjust Idle Stop Solenoid (turn solenoid body, using hex
nut) to obtain:
600 rpm on vehicles equipped with Air Injection
Reactor System (State of California Vehicles).
700 rpm on vehicles not equipped with Air Injection
Reactor System.
Reconnect distributor spark advance hose.
•
307 Cu. In. (Two-Barrel Carburetor)
On Light-Duty vehicles, disconnect &quot;Fuel Tank&quot; line
from Evaporation Emission vapor canister.
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
LIGHT DUTY TRUCK SERVICE MANUAL
6 -1 0 ENGINE
SINGLE-BARREL
TW O -B AR REL
IDLE M IXTURE SC REW
IDLE MIXTURE SC REW S
FOUR-BARREL
IDLE M IXTURE SC RE W S
CEC S O L E N O ID
IDLE SPEED (S O L E N O ID ) SC REW
IDLE SPEED (S O L E N O ID ) SC R E W
Fig. 16—Idle Speed and Mixture Screws
HICLE EMISSION CONTROL INFORMATION
G EN ER A L MOTORS CORPORATION
2.
3.
4.
5.
6
7.
8
[ qm ]
DWELL
fcNTS WITH ENGINE AT NORMAL OPERATING TEM P,
TIMING ( BTDC@RPM)
: INSTALLED. AND DISTR VACUUM LINE DISCONNECT
SPARK
PLUG GAP
UM LINE WHEN ADJUSTMENTS ARE COMPLETED
BLOCK DRIVE WHEELS
SOLENOID SCREW (RPM)
f'FUOM VAPOR CANISTER.
FAST IDLE SCREW (RPM)
S fT DWELL AND TIMING’ AT SPECIFIED RPM
IDLE MIXTURE SETTING
ADJUST CARBURETOR SOLENOID SCREW TO SPECIFIED RPM
WITH TRANSMISSION IN PARK OR NEUTRAL. ADJUST FAST IDLE SCREW TO SPECIFIED
SPEED ON TOP STEP OF CAM. VAC. SPARK CONN. FOR AUTO TRANS
RECONNECT FUEL TANK HOSE TO VAPOR CANISTER
IDLE MIXTURE PRESET AT FACTORY DO NOT REMOVE CAPS
IF CARBURETOR IS REPAIRED OR IDLE MIXTURE SCREW CAPS HAVE BEEN REMOVED. RESET IDLE MIXTURE BY USING
*/4 TURN RICH FROM LEAN ROLL METHOD. INSTALL REPLACEMENT IDLE MIXTURE SCREW CAPS PROCURED FROM DEALER.
REMOVAL OF MIXTURE SCREW CAPS AND ALTERING TO OTHER THAN SPECIFIED IDLE MIXTURE SETTING
MAY VIOLATE FEDERAL AND/OR CALIFORNIA AND OTHER STATE LAWS.
.( CONFORMS II
/^W R
•/&laquo; TURN RICH FROM LEAN ROLL
CALIFORNIA III
ENGINE EXHAUST EMISSION CONTROL INFORMATION
G EN ER A L MOTORS CORPORATION
MAKE IDLE SPEED (CARBURETOR SCREW OR SOLENOID SCREW) AND TIMING ADJUSTMENTS AT SPECIFIED RPM WITH ENGINE AT NORMAL
OPERATING TEMP, CHOKE OPEN. AIR COND OFF. AIR CLEANER INSTALLED. DISTR. VACUUM LINE DISCONNECTED AND PLUGGED RECONNECT ALL
FITTINGS WHEN SETTINGS ARE COMPLETED. SET PARKING BRAKE AND BLOCK DRIVE WHEELS. PUT TRANS IN PARK OR NEUT. FOR ALL SETTINGS.
LEAN DROP IDLE MIXTURE
IDLE MIXTURE PRESET AT FACTORY DO NOT REMOVE CAPS. REMOVAL OF MIXTURE SCREW CAPS AND ALTERING TO OTHER THAN SPECIFIED IDLE
MIXTURE SETTING MAY VIOLATE FEDERAL AND/OR SOME STATE LAWS. IF CARBURETOR IS REPAIRED OR IDLE MIXTURE SCREW CAPS HAVE BEEN
REMOVED, RESET IDLE MIXTURE BY LEAN DROP METHOD. IN STALL REPLACEMENT IDLE MIXTURE SCREW CAPS PROCURED FROM DEALER.
f&raquo;&raquo; GASOLINE WHO MW PUTT ENGINES_ _ _ _ _ _ _ _ _ _ _ PT NO. 330S64 J 7
I REGULATIONS APPLICAIIE Tl
Fig. 17—Tune-Up Decal
On Heavy-Duty vehicles - C-K-P20 (except C-K20
suburban) and C-P30 - adjust carburetor Idle Speed
Screw to obtain 600 rpm with automatic transmission in
“Park” and manual transmission in neutral.
On Light-Duty Vehicles - C-G-K10 and C20 Suburban adjust Idle Stop Solenoid (turn solenoid body, using hex
nut) to obtain 600 rpm with automatic transmission in
Drive - 900 rpm with manual transmission in neutral.
On Light-Duty vehicles, disconnect the Idle Stop
Solenoid electrical lead. Adjust low idle screw (located
inside the solenoid hex nut) with screw on low step of
cam, to obtain
rpm - automatic transmission in
Drive and manual transmission in neutral - reconnect
Idle Stop Solenoid electrical lead.
.Reconnect “Fuel Tank” line to v va^$^ canister and
reconnect distributor spark advanceHfegase^
•
350 Cu. In. (Four-Barrel Carburetor)
On Light-Duty vehicles, disconnect “Fuel Tank” line
from Evaporation Emission vapor canister.
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
On Heavy-Duty vehicles, adjust carburetor Idle Speed
Screw to obtain 600 rpm with automatic transmission in
“Park” and manual transmission in neutral.
On Light Duty vehicles, adjust Idle Stop Solenoid (turn
solenoid body, using hex nut) to obtain 600 rpm with
automatic transmission in Drive; 900 rpm with manual
transmission in neutral.
On Light-Duty vehicles with automatic transmission,
reconnect distributor spark advance hose. Adjust fast idle
LIGHT DUTY T R q p ^ E t &amp; IC E MANUAL
EN G IN E * 6-11
screw to obtain 1600 rpm with screw on top step of fast
idle cam.
On Light-Duty vehicles with manual transmission, adjust
fast idle screw to obtain 1300 rpm with screw on top step
of fast idle cam and distributor spark advance hose
disconnected.
Reconnect “Fuel Tank” line to vapor canister and
reconnect distributor spark advance hose.
•
454 Cu. In. (Four-Barrel Carburetor)
On Light-Duty vehicles, disconnect “Fuel Tank” line
from Evaporation Emission vapor canister.
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
Adjust Idle Stop Solenoid (turn solenoid body, using hex
nut) to obtain:
700 rpm on all Heavy Duty vehicles - automatic
transmission in “Park” ; manuaPMransmission in
neutral.
6V00 rpm on Light-Duty vehicles with automatic
transmission (in Drive).
900 rpm on Light-Duty vehicles with manual
transmission (in neutral).
On Light Duty vehicles with automatic transmission,
_ig&pound;onnect distributor spark advance hose. Adjust fast idle
screw to obtain 1600 rpm with screw on top step of fast
idle cam.
^
On Light-Duty vehicles with manual transmission, adjust
fast idle screw to obtain 1600 rpm with screw on top step
of fast idle cam and distributor spark advaii%&quot; hos&pound;
disconnected.
:
v*8&quot;'
Reconnect “Fuel Tank” line to vaporânister and
reconnect distributor spark advance hose.
C
A D D ITIO N A L CHECKS A N D ADJUSTMENTS
CYLINDER BALANCE TEST
(FIG. 1 8 )
It is often difficult to locate a weak cylinder. A
compression test, for example, will not locate a leaky
intake manifold, a valve not opening properly due to a
worn camshaft, or a defective spark plug.
With the cylinder balance test, the power output of one
cylinder may be checked against another, using a set of
grounding leads. When the power output of each
cylinder is pot equal, the engine will lose power and run
roughly.
Perform a cylinder balance test as follows:
1. Connect the tachometer and vacuum gauge.
2. Start engine and run at 1500 rpm.
3. Ground large clip of grounding leads and connect
individual leads to all spark plugs except the pair
being tested.
Divide the firing order in half and arrange one half
over the other. The cylinders to be tested together
appear one over the other.
L6 Firing Order
1-5-3-6-2-4 = 1-5-3 = 1-6, 5-2, 3-4
BATTERY
The battery should be checked with special testing
equipment and to the equipment manufacturers
specifications. See Section 6 Y for complete information
on battery tests.
IG N ITIO N
The following additional ignition checks may be made
with any of several pieces of equipment available for
uncovering the source of engine difficulties. The specific
operating instructions of the equipment manufacturer
should be followed.
• Cranking voltage
• Ignition switch
• Distributor resistance
V 8 Fifing Order
1-8-4-3-6-5-7-2 = 1-84-3 = 1-6, 8-5, 4-7,3-2
6-5-7-2
4. Operate engine on each pair of cylinders in turn
and note engine rpm and manifold vacuum for
each pair. A variation of more than 1 inch of
vacuum or 40 rpm between pairs of cylinders being
tested indicates that the cylinders are off balance.
LIGHT DUTY TRUCK SERVICE MAfUAL
■V
6 -1 2 ENQINE
• Secondary Resistance
• Ignitioft’oulput and secondary leakage
Cranking Voltage (Fig. 19)
1. Disconnect coil .primary lead at the coil negative
terminal , to prevent engine from firing during
cranking.
\
2. Connect voltmeter between primary terminal of coil
(resistance wire side) and ground.
3. Operate starting mbtor.
a. If voltage is 9 volts or more and cranking speed
is satisfactory, the battery, starter, cables, starter
switch and ignition circuit to coil (by-passing
resistance wire) are in good condition.
\
b. If below 9 volts, check circuit until difficulty is
located.
Meter reading below specification-W eak battery;
defective cables^ connections, switch or starter;
defective ignition circuit to coil.
Cranking speed below norm al-Excessive resistance
in cables or starting motor; excessive mechanical
drag in engine.
Uneven cranking sp&laquo;ec&pound;-Uneven compression,
defective starter to starter drive.
Fig. 19-Testing Cranking Voltage
Ignition Switch
With voltmeter connected as described for the Cranking
Voltage Test, turn ignition switch to ON. Voltage should
drop to 5 to 7 volts as current is now passing through
high resistance wire connected between ignition switch
and ( + ) positive terminal of coil. If battery voltage of 12
volts is obtained, the starter solenoid is by-passing the
high resistance wire connected between ignition switch
and ( + ) positive terminal of coil, thus the starter
solenoid is not functioning properly to by-pass the
ignition resistance wire or the ignition circuit is
incorrectly wired.
NOTE: The voltage drop (12 to 5-7 volts) will
only take place when the points are closed. If
the points are open, the path through the
resistance wire will not be completed.
Distributor Resistance
Use equipment as directed by manufacturer. Excessive
resistance in primary circuit must be eliminated before
continuing with test procedure.
Secondary Resistance
Use equipment as directed by manufacturer.
• Uniform “normal readings” as specified by
manufacturer indicate all secondary circuit compo&shy;
nents are in good condition.
• If all readings are “below normal”, check for
corroded coil tower terminal, poorly connected or
broken coil wire, center cap electrode or rotor tip
burned, or an open secondary in coil.
• If readings are “higher than normal” at two or
more plugs adjacent in firing order, cross firing is
Fig. 20—Cooling System Pressure Check
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
occurring in distributor cap or between spark plug
cables concerned.
• If meter reads off scale to left, the coil polarity is
reversed. Check for reversed coil primary wires,
wrong coil or reversed vehicle battery connections.
Ignition Output and Secondary Leakage
Use equipment as directed by manufacturer.
• GOOD readings indicate both ignition output and
secondary insulation are good.
• If all readings are BAD or if ignition test calibrator
cannot be adjusted to Set Line, check for high
resistance in primary circuit, defective distributor
points, coil or condenser.
• If readings are BAD when certain plug wires are
lifted off, check for cracks or carbon tracks in
distributor cap or defective insulation on those plug
wires being lifted off.
CARBURETOR
Refer to Section 6 M to perform adjustments such as float
level, pump rod and vacuum break.
FUEL PUMP
If the owner has complained of poor high speed
performance, the fuel pump may be at fault. Too low a
pump pressure or volume will cause a high speed “miss”
because of lack of fuel delivered to the carburetor, while
too high a pressure will cause carburetor flooding. Check
fuel pump as outlined in Section 6 M.
COOLING SYSTEM
The following test may be performed with pressure
testing equipment available commercially for this
purpose. This test provides an excellent means of
detecting internal or external leaks within the cooling
system.
1. Remove radiator cap.
2. Apply a test pressure of 3 pounds higher than the
radiator cap (fig. 20), i.e. 18 pounds for a 15 pound
cap.
3. If the pressure will not hold, there is either an
internal or external leak in the system.
CYLINDER HEAD TORQUE AND
VALVE ADJUSTMENT
Retorquing the cylinder head bolts is not necessary
unless a gasket has been replaced, or a leak is suspected.
Valve lash must always be adjusted after the head has
been torqued.
Valve Adjustment
1. Remove rocker arm cover(s) and gasket(s).
CAUTION: Do not pry rocker arm cover loose.
Gaskets adhering to cylinder head and rocker
arm cover may be sheared by bumping end of
6 -1 3
rocker arm cover rearward with palm of hand
or a rubber mallet.
2. Adjust valves on L -6 engines as follows:
a. Mark distributor housing, with chalk, at number
one and number six positions (plug wire) then
disconnect plug wires at spark plugs and coil
and remove distributor cap and plug wire
assembly (if not previously done).
b. Crank engine until distributor rotor points to
number one cylinder position and breaker
points are open. The following valves can be
adjusted with engine in number one firing
position:
Number one cylinder-Exhaust and Intake
Number two cylinder-Intake
Number three cylinder-Exhaust
Number four cylinder-Intake
Number five cylinder-Exhaust
c. Back out adjusting nut until lash is felt at the
push rod then turn in adjusting nut until all lash
is removed. This can be determined by checking
push rod end play while turning adjusting nut
(fig. 21 ). When play Has been removed, turn
adjusting nut in one full additional turn (to
center lifter plunger).
d. Crank engine until distributor rotor points to
number six position and breaker points are
open.
The following valves can be adjusted with engine in
number six firing position:
Number two cylinder-Exhaust
Number three cylinder-Intake ' Number four cylinder-Exhaust
Number five cylinder-Intake
Number six cylinder-Intake and Exhaust
3. Adjust valves on V -8 engines using the following
procedures:
a. Crank engine until mark on torsional damper
lines up with center or “ 0 ” mark on the timing
tab and the engine is in the number 1 firing
position. This may be determined by placing
fingers on the number 1 cylinder valve as the
mark on the damper comes near the “ 0 ” mark
on the front cover. If the valves are not moving,
the engine is in the number 1 firing position. If
the valves move as the mark comes up to the
timing tab, the engine is in number 6 firing
position and crankshaft should be rotated one
more revolution to reach the number 1 position.
b. Valve adjustment is made by backing off the
adjusting nut (rocker arm stud nut) until there is
play in the push rod and then tighten nut to just
remove all push rod to rocker arm clearance.
This may be determined by rotating push rod
LIGHT DUTY TRUCK SERVICE MANUAL
6 -1 4 ENGINE
Fig. 22—Valve Adjustment (V8 Engine)
Fig. 21—Valve Adjustment (L6 Engine)
with fingers as the nut is tightened (fig. 22 ).
When push rod does not readily move in
relation to the rocker arm, the clearance has
been eliminated. The adjusting nut should then
be tightened an additional 1 turn to place the
hydraulic lifter plunger in the center of its
travel. No other adjustment is required.
c. With the engine in the number 1 firing position
as determined above, the following valves may
be adjusted.
Exhaust - 1, 3, 4, 8
Intake - 1, 2, 5, 7
d. Crank the engine one revolution until the
pointer “0 ” mark and torsional damper mark
4.
5.
6.
7.
are again in alignment. This is number 6 firing
position. With the engine in this position the
following valve may be adjusted.
Exhaust - 2, 5, 6 , 7
Intake - 3, 4, 6 , 8
Clean gasket surfaces on cylinder head(s) and
rocker arm cover(s) with degreaser, then install
rocker arm cover(s), using new gasket(s), and torque
bolts to specifications.
Install distributor cap and spark plug wire
assembly.
Install rocker arm cover as outlined.
Adjust carburetor idle speed.
THEORY OF OPERATION
All engines operate on the 4-stroke cycle principle (Fig.
ID and 2D). During this cycle the piston travels the
length of its stroke four times. As the piston travels the
length of its stroke (up or down) the crankshaft is
rotated halfway (180 degrees). To accomplish one cycle
of the 4 -stroke cycle, the crankshaft rotates two complete
turns; the camshaft, which controls the valves, is driven
by the crankshaft at half crankshaft speed. Valve action,
intake and exhaust, occurs once in each 4-stroke cycle
and the piston acts as an air pump during the two
remaining strokes.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
6 -1 5
Fig. ID —Sectional View of Eight-Cylinder Engine
LIGHT DUTY TRUCK SERVICE MANUAL
6-16
ENGINE
Fig. 2D—Sectional View of Six-Cylinder Engine
Intake Stroke
The intake valve is opened as the piston moves down in
the cylinder (Fig. 3D). The piston traveling downward in
the cylinder creates an area of pressure lower than that
of the atmosphere surrounding the engine. Atmospheric
pressure will cause air to flow into this low pressure area.
By directing the air flow through the carburetor, a
measured amount of vaporized fuel is added. When the
piston reaches the bottom of the intake stroke, the
cylinder is filled with air and vaporized fuel. The exhaust
valve is closed during the intake stroke.
down. This downward motion of the piston is
transmitted through the connecting rod and is converted
to rotary motion by the crankshaft. Both the intake and
exhaust valve are closed during the power stroke (Fig.
5D).
Exhaust Stroke
When the piston starts to move upward, the compression
stroke begins (Fig. 4D). The intake valve closes, trapping
the air-fuel mixture in the cylinder. The upward
movement of the piston compresses the mixture to a
fraction of its original volume; exact pressure depends
principally on the compression ratio of the engine.
The exhaust valve opens just before the piston completes
the power stroke (Fig. 6 D). Pressure in the cylinder at
this time causes the exhaust gas to rush into the exhaust
manifold. The upward movement of the piston on its
exhaust stroke expels most of the remaining exhaust gas.
As the piston pauses momentarily at the top of the
exhaust stroke, the inertia of the exhaust gas tends to
remove any remaining gas in the combustion chamber;
however, a small amount of exhaust gas always remains
to be mixed with the incoming mixture - this unexpelled
gas is captured in the clearance area between the piston
and the cylinder head.
Power Stroke
Combustion
The power stroke is produced by igniting the compressed
air-fuel mixture. When the spark plug arcs, an explosion
does not occur. Instead, the mixture ignites and burns
very rapidly during the power stroke. The extremely high
temperature expands the gases, creating a very high
pressure on the top of the piston which drives the piston
The power delivered from the piston to the crankshaft is
the result of a pressure increase in the gas mixture above
the piston. This pressure increase occurs as the mixture is
heated, first by compression, and then — on the down
stroke — by burning. The burning fuel supplies heat that
raises temperature and at the same time also raises
Compression Stroke
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
6 -1 7
Fig. 4D—Piston Compression Stroke
Fig. 3D—Piston Intake Stroke
pressure. Actually, about 75 per cent of the mixture in
the cylinder is composed of nitrogen gas that does not
burn but expands when heated by the burning of the
combustible elements, and this expanding nitrogen
supplies most of the pressure on the piston.
The fuel and oxygen must burn smoothly within the
combustion chamber to take full advantage of this
heating effect. Maximum power would not be delivered
to the piston if an explosion took place, because the
entire force would be spent in one sharp hammer-like
blow, occurring too fast for the piston to follow.
Instead, burning must take place evenly as the flame
moves across the combustion chamber. Burning must be
completed by the time the piston is about half-way down
so that maximum pressure will be developed in the
cylinder at the time the piston sends its greatest force to
the crankshaft. This will be when the mechanical
advantage of the connecting rod and crankshaft is at a
maximum.
At the beginning of the power stroke, as the piston is
driven downward by this pressure the volume above the
piston increases, which would normally allow the
pressure in the cylinder to drop. However, the
combustion process is still occurring and this continues to
raise the temperature of the gases, expanding them and
maintaining a continuous pressure on the piston as it
travels downward. This provides a smooth application of
power throughout the effective part of the power stroke
to make the most efficient use of the energy released by
the burning fuel.
An internal combustion engine actually runs on heated
air, the air being composed mainly of inert nitrogen.
The fuel is used, not to cause explosions, but to cause
high pressure within the cylinder to push the piston
down smoothly during the power stroke.
Compression Ratio
The compression ratio is a comparison of the volume of
the cylinder and combustion chamber when the piston is
all the way down, to the volume remaining when the
piston is all the way up.
The main advantage of a high compression ratio is that
it enables the engine to develop more power from a
given charge of fuel. The combustion pressure exerted
downward on the piston is always 3 or 4 times as great as
the compression pressure. Consequently, an increase in
LIGHT DUTY TRUCK SERVICE MANUAL
6 -1 8 ENGINE
Fig. 6D—Piston Exhaust Stroke
Fig. 5D—Piston Power Stroke
compression pressure (input) means at least three times
as great an increase in combustion pressure (output).
Valve Timing
As in most 4-stroke cycle engines, the intake valve begins
to open before the piston reaches the top, and the
exhaust valve remains open until after top dead center.
This means that both valves are open for a short period
of time. This condition is called valve overlap (Fig. 7D).
The valve timing is arranged this way to use the inertia
of the gas in evacuating and in filling the cylinders.
When the air-fuel mixture and exhaust gases move in or
out of the cylinder, its weight gives it momentum in the
established direction. When a valve opens, the initial air
flow is slow. Valve timing allows for this lag in starting
and stopping in the flow. In order to pack the maximum
air-fuel mixture into the cylinder, each valve opens
earlier and closes later than would be necessary if the
mixture were weightless.
On the intake stroke, the exhaust valve stays open a little
after top center to take advantage of the momentum of
the exhaust gases rushing out through the valve, even
though the piston has started down. With the exhaust
TOP DEAD CENTER
INTAKE VALVEOPENS
INTAKE
VALVE
CLOSES
EXHAUST VALVE
CLOSES
EXHAUST
VALVE
OPENS
BOTTOM DEAD CENTER
Fig. 7D—Typical Valve Overlap (720-degree spiral)
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
6 -1 9
valve still open, the cylinder continues to empty itself
because of this momentum.
On the compression stroke, the intake valve stays open
past bottom center because incoming gases will continue
to pack their way in for a short time after the piston
reverses direction, due to their momentum.
On the power stroke, the exhaust valve opens before
bottom center to get the exhaust gases started out of the
cylinder.
On the exhaust stroke, the intake valve opens before top
center to start the air fuel mixture moving into the
cylinder.
Valve timing is not variable with speed and load as is
ignition timing. Except for very small variations due to
the stack of tolerances in the valve train (Fig. 8 D), valves
always open and close at the same time in the cycle.
There is, however, one particular speed for a given
engine at which the air-fuel mixture will pack itself into
the cylinders most effectively. This is the speed at which
the engine puts out its peak torque. At low engine
speeds, compression is somewhat suppressed due to the
slight reverse flow through the valves just as they open or
close, when the mixture is not moving fast enough to
take advantage of the time lag. At very high speeds, the
valve timing does not allow quite enough time during the
opening and closing periods for effective packing of the
air-fuel mixture into the cylinders.
Fig. 8D—Valve System Components
ENGINE MECHANICAL
IN-LINE ENGINES
INDEX
General Description............................................................
Component Replacement and Adjustment.................
Engine Assembly................................................................
Removal (C, K and P Series)....................................
Removal (G Series)........................................................
Installation (C, K and P Series)...............................
Installation (G Series)...................................................
Manifold Assembly...........................................................
Removal..............................................................................
Installation.........................................................................
Rocker Arm Cover............................................................
Removal..............................................................................
Installation.........................................................................
Valve Mechanism...............................................................
Removal..............................................................................
Installation and Adjustment........................................
Valve Lifters........................................................................
Locating Noisy Lifters..................................................
Removal..............................................................................
Installation.........................................................................
Valve Stem Oil Seal and/or Valve Spring..............
6-20
6-20
6-20
6-20
6-22
6-23
6-24
6-25
6-25
6-25
6-26
6-26
6-26
6-26
6-26
6-26
6-26
6-27
6-27
6-27
6-27
Replacement......................................................................
Cylinder Head Assemblies..............................................
Removal...............................................................................
Installation.........................................................................
Oil P an ..................................................................................
Removal...............................................................................
Installation.........................................................................
Oil Pump...............................................................................
Removal...............................................................................
Installation.........................................................................
Oil Seal (Rear M ain)......................................................
Replacement......................................................................
Torsional Damper..............................................................
Removal..............................................................................
Installation.........................................................................
Crankcase Front Cover...................................................
Removal..............................................................................
Installation.........................................................................
Oil Seal (Front Cover)....................................................
Replacement......................................................................
Camshaft...............................................................................
6-27
6-28
6-28
6-28
6-28
6-28
6-28
6-29
6-29
6-29
6-29
6-29
6-30
6-30
6-30
6-31
6-31
6-31
6-32
6-32
6-33
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 2 0 ENGINE
Measuring Lobe Lift .........................................................
Removal .................................................. ...........................
Installation ..........................................................................
Timing Gears ......................................................................
Replacement ......................................................................
Flywheel ...............................................................................
6-33
6-34
6-34
6-35
6-35
6-35
Removal .............................................................................. 6-35
Installation .......................................................................... 6-35
Engine Mounts...................................................................... .6-36
Checking Engine Mounts ................................................ 6-36
Replacement (Front) ........................................................6-36
Replacement (Rear) ......................................................... 6-36
GENERAL DESCRIPTION
The In-Line engines covered in this section are the 250
and 292 cu. in. L6 engines used in 10-30 Series truck
vehicles (fig. 1L).
This section covers the removal and installation of
engine assemblies, the removal, installation and
adjustment of some sub-assemblies and replacement of
some components. For service to all components and
sub-assemblies (after removal) and removal of some
sub-assemblies, refer to Section 6 of the Overhaul
Manual.
Because of the interchangeability and similarity of many
engine sub-assemblies and parts, regardless of which
truck vehicle they are used in, typical illustrations and
procedures are used (except where specific illustrations or
procedures are necessary to clarify the operation).
Although illustrations showing bench operations are
used, most single operations, when not part of a general
overhaul, should be performed (if practical) with the
engine in the vehicle.
C O M PO N EN T REPLACEMENT A N D ADJUSTMENT
Engine Assembly
Removal (C, K and P Series)
1. Disconnect battery cables and drain cooling system.
2. Remove the air cleaner.
3. Perform the following preliminary operations.
ON CS 10-20-30, KS 10-20 SERIES:
Remove the hood as outlined in Section 11.
Remove the radiator and shroud as outlined in
Section 13.
ON PS 10-20-30 SERIES:
Remove the engine box and hood as outlined in
Section 11.
Remove the battery.
Remove the radiator and shroud as outlined in
Section 13.
4. Disconnect wires at:
Starter Solenoid.
Delcotron.
Temperature Switch.
Oil Pressure Switch.
Coil.
CEC Solenoid.
5. Disconnect:
Accelerator linkage at manifold bellcrank.
Fuel line (from tank) at fuel pump.
Heater hoses at engine connection.
Oil pressure gauge line (if so equipped).
Vacuum lines at engine (as required).
• Evaporation Emission System lines at carburetor.
• Power steering pump at engine bracket and lay
aside (if so equipped).
• Ground straps at engine.
• Exhaust pipe at manifold.
NOTE: Hang exhaust pipe at frame with
wire.
6 . Remove fan and pulley as outlined in Section 6 K.
7. Remove clutch cross-shaft (if so equipped).
8 . Perform the following operations:
• Remove the rocker arm cover as outlined.
• Attach lifting device or chain to engine lifting
brackets and take engine weight off mounts.
ON ALL SERIES EXCEPT CS 10-20-30:
• Support transmission and disconnect from
engine. Refer to Section 7.
• Remove engine mount bolts.
ON CS 10-20-30:
• Remove propeller shaft as outlined in Section 4.
NOTE: If plug for propeller shaft opening in
transmission is not available, drain
transmission.
Disconnect TCS switch at transmission.
Disconnect speedometer cable at transmission.
Disconnect shift linkage at transmission.
Disconnect clutch linkage (as required).
Remove engine mount bolts.
Transmission cooler lines (if so equipped).
E N G IN E
6-21
Fig. 1 L —Six-C ylinder Engine
9. Remove engine from vehicle as follows:
CAUTION: Check often during engine removal
to be sure all necessary disconnects have been
made.
ON CS 10-20-30 SERIES:
• On vehicles with automatic or four speed
transmission, remove rear mount crossmember.
• Raise engine and transmission assembly and pull
forward until removed.
ON KS 10-20 SERIES:
• Raise engine and pull forward until disconnected
from transmission.
• Continue to raise engine until removed from
vehicle.
ON PS 10-20-30 SERIES:
• Raise engine and push forward to clear cross&shy;
member and disconnect from transmission.
• Remove engine from vehicle.
10. If engine is to be mounted in an engine stand
perform the following:
ON CS 10-20-30:
• Remove synchromesh transmission and clutch (if
so equipped).
a. Remove clutch housing rear cover bolts.
b. Remove bolts attaching the clutch housing to
engine block then remove transmission and
clutch housing as a unit.
NOTE: Support the transmission as the last
mounting bolt is removed and as it is being
pulled away from the engine, to prevent
damage to clutch disc.
c. Remove starter and clutch housing rear cover.
d. Loosen clutch mounting bolts a turn at a time
(to prevent distortion of clutch cover) until the
spring pressure is released. Remove all bolts,
clutch disc and pressure plate assembly.
• Remove automatic transmission (if so equipped).
a. Lower engine, secured by the hoist, and support
engine on blocks.
b. Remove starter and converter housing under
pan.
c. Remove flywheel-to-converter attaching bolts.
d. Support transmission on blocks.
e. Disconnect throttle linkage and vacuum modula&shy;
tor line.
f. Remove transmission-to-engine mounting bolts.
g. With the hoist attached, remove blocks from the
engine only and slowly guide the engine from
the transmission.
LIGHT DUTY TRUCK SERVICE MANUAL
6 -2 2 ENGINE
ON ALL SERIES EXCEPT CS 10-20-30:
• Remove clutch housing.
• Loosen clutch mounting bolts a turn at a time (to
prevent distortion of clutch cover) until the
spring pressure is released. Remove all bolts,
clutch disc and pressure plate assembly.
11. Mount engine in engine stand and remove lifting
device and lifting adapter.
Removal (G Series)
1. Remove engine cover and position it out of way.
2. Disconnect battery ground cable at engine block
and at battery.
3. Drain cooling system and disconnect heater hoses
at engine; disconnect radiator hoses at radiator.
4. Disconnect automatic transmission cooler lines at
radiator.
5. Remove fan guard and radiator.
6 . Disconnect oil pressure gauge, if so equipped.
7. Disconnect engine wiring harness at dash panel
junction block.
8 . Disconnect Delcotron wires at rear of Delcotron.
9. Disconnect TCS system electrical leads at car&shy;
buretor mounted CEC valve and at temperature
switch - remove harness from clips and position it
to one side.
10. Disconnect Evaporation Control System lines at air
cleaner and at carburetor - position lines to one
side.
11. Disconnect accelerator linkage at dash panel
mounted bell crank.
12. Disconnect power brake vacuum line at inlet
manifold.
13. Raise vehicle on a hoist and disconnect:
Fig. 2L—Brake Line Disconnects
•
•
•
•
Fuel line (from tank) at fuel pump.
Engine ground strap(s).
Steering idler arm at frame.
Steering pitman arm at steering gear as outlined
in Section 9.
• Battery positive cable at starter.
• Speedometer cable at transmission.
• TCS switch at transmission - remove bell
housing mounted clip and position wiring to one
side.
• Exhaust pipe at manifold and at pipe hangers then remove exhaust system from vehicle.
• Transmission at crossmember.
• Stabilizer shaft at frame brackets.
14. Disconnect clutch linkage and/or transmission
linkage and remove cross shaft as outlined in
Section 7.
Fig. 4L-Suspension-to-Frame Attaching Bolts
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
15. Disconnect shock absorbers at frame or at lower
control arm attachment and position shocks up and
rearward.
16. Remove propeller shaft as outlined in Section 4 install plug in transmission extension.
17. Disconnect front brake pipe at equalizer tee and
disconnect rear brake pipe at connector at left
frame rail (Fig. 2L).
18. Disconnect rear brake pipe at right frame rail
connector (Fig. 3L).
19. Remove transmission support frame-to-crossmember attaching nuts - do not remove bolts at this
time.
20. Remove the six (3 on each side) vertically driven
front crossmember-to-frame attaching bolts (Fig.
3L).
21. Remove the four (2 on each side) frame-to-upper
control arm (inside) attaching bolts (Fig. 4L).
22. Lower the vehicle on hoist so that weight of vehicle
is on hoist but with wheels touching floor and
suspension at curb height.
23. Install wood blocks between oil pan and crossmem&shy;
ber to stabilize engine assembly (Fig. 5L).
24. Position floor jack under vehicle so that jack pad is
aligned under transmission and, using a block of
wood to protect transmission, support transmission
with jack.
25. Remove transmission support crossmember.
26. Remove the four (2 on each side) remaining
suspension-to-frame (outside) retaining bolts (Fig.
4L).
27. Raise vehicle slowly, leaving suspension and power
train on the floor until sufficient clearance is
obtained for removing engine.
CAU TIO N: Check often when raising the
vehicle to make sure that all disconnects have
been made and that vehicle is positioned
properly on hoist.
28. Roll the power train and suspension assembly to
the work area and position jack stand under
transmission extension - remove floor jack.
29. Place floor jack under suspension crossmember
and raise jack so that weight of assembly is
supported on jack pad.
30. Attach lifting adapter at engine lifting brackets.
31. Attach lifting device to support engine, remove
engine mount through bolts and remove engine
assembly from crossmember.
32 Remove synchromesh transmission and clutch (if so
equipped).
a. Remove clutch housing rear cover bolts.
b. Remove bolts attaching the clutch housing to
6 -2 3
Fig. 5 L —F loor Jack Location Under Transmission (L-6)
engine block, then remove transmission and
clutch housing as a unit.
NOTE: Support the transmission as the last
mounting bolt is removed and as it is being
pulled away from the engine, to prevent
damage to clutch disc.
c. Remove starter and clutch housing rear cover.
d. Loosen clutch mounting bolts a turn at a time
(to prevent distortion of clutch cover) until the
spring pressure is released. Remove all bolts,
clutch disc and pressure plate assembly.
33. Remove automatic transmission (if so equipped).
a. Lower engine, secured by the hoist, and support
engine on blocks.
b. Remove starter and converter housing
underpan.
c. Remove flywheel-to-converter attaching bolts.
d. Support transmission on blocks.
e. Disconnect detent cable on Turbo Hydra-Matic.
f. Remove transmission-to-engine mounting bolts.
g. With the hoist attached, remove blocks from the
engine only and slowly guide the engine away
from the transmission.
34. Mount engine in engine stand and remove lifting
device and lifting adapter.
Installation (C, K and P Series)
1. If engine was mounted in an engine stand, attach
lifting adapter to engine lift brackets then using
lifting device, remove engine from stand and
perform the following:
ON CS 10-20-30:
LIGHT DUTY TRUCK SERVICE MANUAL
6 -2 4 ENGINE
2.
3.
4.
5.
6.
• Install synchromesh transmission and clutch (if
so equipped).
a. Install the clutch assembly on flywheel as
outlined in Section 7.
b. Install clutch housing rear cover and starter.
c. Install the transmission and clutch housing as
outlined in Section 7.
d. Install clutch housing rear cover bolts and
torque to specifications.
• Install automatic transmission (if so equipped).
a. Position engine adjacent to the transmission and
align the convertor with the flywheel.
b. Bolt transmission to engine then raise engine
and transmission assembly and install flywheel
to convertor bolts.
c. Install convertor housing underpan and starter.
d. Connect throttle linkage and vacuum modulator
line.
ON ALL SERIES EXCEPT CS 10-20-30:
• Install clutch assembly and clutch housing as
outlined in Section 7.
Install engine in vehicle as follows:
ON ALL SERIES EXCEPT CS 10-20-30:
• Install engine, and lower until transmission shaft
lines up with clutch.
• Push engine rearward and rotate crankshaft until
transmission shaft and clutch engage.
• Install the engine mount bolts and torque to
specifications.
• Connect transmission to engine.
ON CS 10-20-30 SERIES:
• Lower engine and transmission assembly and
push rearward until engine mounts line up.
• On vehicles with automatic or four speed
transmissions,
install
rear
mount
crossmember.
•Install the engine mount bolts and torque to
specifications.
•Install the propeller shaft as outlined in Section
4.
ON ALL SERIES:
• Remove the lifting device and lifting adapter
from engine lift brackets.
Connect transmission linkage (as required).
Install clutch cross-shaft (as required).
Install fan and pulley as outlined in Section 6 K.
Connect:
• Transmission cooler lines (if so equipped).
• Exhaust pipe at manifold.
• Power steering pump (as required).
• Vacuum lines at engine (as required).
• Oil pressure gauge line (as required).
• Heater hoses at engine connection.
• Fuel line at fuel pump.
• Accelerator linkage at manifold bellcrank.
• TCS switch at transmission.
• Evaporation Emission System hoses at canister.
7. Connect wires at:
• Coil
• Oil Pressure Switch
• Temperature Switch
• Delcotron
• Starter Solenoid
• CEC Solenoid
8 . Complete installation as follows:
ON PS 10-20-30 SERIES:
• Install the radiator and shroud as outlined in
Section 13.
• Install the battery.
• Install the floor panel and engine box as outlined
in Section 1B.
ON CS 10-20-30, KS 10-20 SERIES:
• Install the radiator and shroud as outlined in
Section 13.
• Install the hood as outlined in Section 11.
9. Install the air cleaner, connect battery cables, fill
cooling system and crankcase then start engine and
check for leaks.
Installation
(G
Series)
1. If engine was mounted in an engine stand, attach
lifting adapter-to-engine, then using lifting device,
remove engine from stand and perform the
following:
• Install synchromesh transmission and clutch (if
so equipped).
a. Install the clutch assembly on flywheel as
outlined in Section 7.
b. Install clutch housing rear cover and starter.
c. Install the transmission and clutch housing as
outlined in Section 7.
d. Install clutch housing bolts and torque to
specifications.
• Install automatic transmission (if so equipped).
a. Position engine adjacent to the transmission and
align the converter with the flywheel.
b. Bolt transmission to engine and then raise
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
engine and transmission assembly and install
flywheel to converter bolts.
c. Install converter housing underpan and starter.
d. Connect throttle linkage and detent cable on
Turbo Hydra-Matic.
Raise engine and align mounts on engine with
brackets on crossmember - install engine mount
through bolts.
Place wood block between oil pan and crossmember
to stabilize power train.
Remove floor jack from under crossmember and
position jack pad under transmission assembly,
using wood blocks at jack pad to protect
transmission.
Remove the lifting device from engine brackets.
Roll the power train and suspension assembly
under vehicle so that crossmember is aligned with
frame.
Slowly lower the vehicle, checking often to assure
that engine components do not interfere with
vehicle as it is being lowered, until suspension to
frame attaching bolt holes are aligned.
Install and securely tighten suspension to-frame
attaching bolts.
Install transmission support crossmember, and
remove floor jack from beneath the transmission.
Raise vehicle on the hoist and install the remaining
suspension-to-frame attaching bolts - torque boltsto-specifications. Torque transmission-to-crossmember and crossmember to frame bolts to
specifications.
Install propeller shaft as outlined in Section 4.
Connect rear brake pipe at right fram e-rail
connector; connect front brake pipe at equalizer tee
and connect rear brake pipe at left frame rail
connector.
Install and torque shock absorber attaching bolts to
specifications. Connect stabilizer shaft to frame.
Install cross shaft and connect clutch linkage and/
or transmission linkage as outlined in Section 7.
Connect the following items:
• Fuel line (from tank) at fuel pump.
• Engine ground strap(s).
• Steering idler arm at frame; then steering
pitman arm at steering gear and torque nut to
specifications.
• Battery positive cable at starter.
• Speedometer cable at transmission.
• TCS switch at transmission - install TCS wire to
clip at transmission/clutch housing.
• Install exhaust system.
6-25
16. Remove wood block placed between crossmember
and oil pan.
17. Lower vehicle on hoist.
18. Connect accelerator linkage at dash panel mounted
bell crank.
19. Connect Evaporation Control System lines at air
cleaner and at carburetor.
20. Connect TCS system electrical leads at carburetor
mounted CEC valve and at temperature switch position harness in rocker arm cover clips.
21. Connect electrical leads at rear of Delcotron.
22. Connect engine wiring harness at dash panel
junction block.
23. Connect oil pressure gauge line if so equipped.
24. Install radiator and fan guard, connect radiator and
heater hoses, install automatic transmission cooler
lines and fill cooling system.
25. Connect battery ground cable at engine block and
at battery.
26. Connect power brake vacuum hose at inlet
manifold fitting.
27. Install engine cover.
28. Bleed front and rear brakes as outlined in Section
5.
29. Start engine, check and add engine coolant as
required and check engine for proper operation.
Manifold Assembly
Removal
1. Remove air cleaner.
2. Disconnect both throttle rods at bellcrank and
remove throttle return spring.
3. Disconnect fuel and vacuum lines and choke cable
at carburetor.
4. Disconnect crankcase ventilation hose at rocker arm
cover.
5. Disconnect exhaust pipe at manifold flange and
discard packing.
6 . Remove manifold attaching bolts and clamps then
remove manifold assembly and discard gaskets.
7. Check for cracks in manifold castings.
8 . Separate manifolds by removing one bolt and two
nuts at center of assembly.
9. Disconnect exhaust gas recirculation valve hose.
Installation
1. Clean gasket surfaces on cylinder head and
manifolds.
2. Lay a straight edge along the full length of the
exhaust port faces and measure any gaps between
the straight edge and the port faces. If at any point
a gap of .015 or more exists, it is likely the
LIGHT DUTY TRUCK SERVICE MANUAL
6 -2 6 ENGINE
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
manifold has distorted to a point where it will not
seat properly. If a good exhaust seal is to be
expected, the exhaust manifold must be replaced.
Reinstall the one bolt and two nuts at the center of
the manifold to finger tight.
Position new gasket over manifold end studs on the
cylinder head.
Install manifold assembly bolts and clamps while
holding manifold assembly in place by hand.
Clean, oil and torque all manifold assembly-tocylinder head bolts and nuts to specifications.
Complete torqueing the inlet to exhaust manifold
bolt and two nuts at the center of the manifold to
specifications.
Connect exhaust pipe to manifold using a new
packing.
Connect crankcase ventilation hose at rocker arm
cover.
Connect exhaust gas recirculation valve hose.
Connect fuel and vacuum lines at carburetor.
Connect throttle rods at bellcrank and install
throttle return spring.
Install air cleaner, start engine, check for leaks and
adjust carburetor idle speed.
and push rods in a rack so that they may be
reinstalled in the same location.
Installation and Adjustment
1.
2.
3.
Rocker Arm Cover
Removal
1. Disconnect crankcase ventilation hose(s) at rocker
arm cover.
2. Remove air cleaner.
3. Disconnect temperature wire from rocker arm cover
clips.
4. Remove air injection pipe support bracket.
5. Remove rocker arm cover.
Installation
1. Clean gasket surfaces on cylinder head and rocker
gasket, install rocker arm cover and torque to
specifications.
2. Connect temperature wire at rocker arm cover clips.
3. Install air cleaner.
4. Connect crankcase ventilation hoses.
5. Install air injection pipe support bracket.
Valve Mechanism
Removal
1. Remove rocker arm cover as outlined.
2. Remove rocker arm nuts, rocker arm balls, rocker
arms and push rods.
NOTE: Place rocker arms, rocker arm balls
4.
5.
6.
NOTE: Whenever new rocker arms and/or
rocker arm balls are being installed, coat
bearing surfaces of rocker arms and rocker
arm balls with “Molykote” or its equivalent.
Install push rods. Be sure push rods seat in lifter
socket.
Install rocker arms, rocker arm balls and rocker
arm nuts. Tighten rocker arm nuts until all lash is
eliminated.
Adjust valves when lifter is on base circle of
camshaft lobe as follows:
a. Mark distributor housing, with chalk, at number
one and number six cylinder positions (plug
wire) then disconnect plug wires at spark plugs
and coil and remove distributor cap and plug
wire assembly (if not previously done).
b. Crank engine until distributor rotor points to
number one cylinder position and breaker
points are open. The following valves can be
adjusted with engine in number one firing
position.
Number one cylinder-Exhaust and Intake
Number two cylinder-Intake
Number three cylinder-Exhaust
Number four cylinder-Intake
Number five cylinder-Exhaust
c. Back out adjusting nut until lash is felt at the
push rod then turn in adjusting nut until all lash
is removed. This can be determined by checking
push rod side play while turning adjusting nut
(fig. 6 L). When play has been removed, turn
adjusting nut in one full additional turn (to
center lifter plunger).
d. Crank engine until distributor rotor points to
number six position and breaker points are
open. The following valves can be adjusted with
engine in number six firing position:
Number two cylinder-Exhaust
Number three cylinder-Intake
Number four cylinder-Exhaust
Number five cylinder-Intake
Number six cylinder-Intake and Exhaust
Install distributor cap and spark plug wire
assembly.
Install rocker arm cover as outlined.
Adjust carburetor idle speed.
Valve Lifters
Hydraulic valve lifters very seldom require attention.
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
6-27
c. Improper adjustment.
3. General Noise Throughout the Valve Train — This
will, in most cases, be caused by either insufficient
oil supply or improper adjustment.
4. Intermittent Clicking — Probable causes are:
a. A microscopic piece of dirt momentarily caught
between ball seat and check valve ball.
b. In rare cases, the ball itself may be out-of-round
or have a flat spot.
c. Improper adjustment.
In most cases, where noise exists in one or more lifters,
all lifter units should be removed, disassembled, cleaned
in a solvent, reassembled, and reinstalled in the engine.
If dirt, varnish, carbon, etc. is shown to exist in one unit,
it more than likely exists in all the units, thus it would
only be a matter of time before all lifters caused trouble.
Removal
Fig. 6L—Valve Adjustment
The lifters are extremely simple in design. Readjust&shy;
ments are not necessary, and servicing of the lifters
requires only that care and cleanliness be exercised in
the handling of parts.
Locating Noisy Lifters
Locate a noisy valve lifter by using a piece of garden
hose approximately four feet in length. Place one end of
the hose near the end of each intake and exhaust valve
with the other end of the hose to the ear. In this manner,
the sound is localized making it easy to determine which
lifter is at fault.
Another method is to place a finger on the face of the
valve spring retainer. If the lifter is not functioning
properly, a distinct shock will be felt when the valve
returns to its seat.
The general types of valve lifter noise are as follows:
1. Hard Rapping Noise — Usually caused by the
plunger becoming tight in the bore of the lifter
body to such an extent that the return spring can no
longer push the plunger back up to working
position. Probable causes are:
a. Excessive varnish or carbon deposit causing
abnormal stickiness.
b. Galling or “pickup” between plunger and bore
of lifter body, usually caused by an abrasive
piece of dirt or metal wedging between plunger
and lifter body.
2. Moderate Rapping Noise — Probable causes are:
a. Excessively high leakdown rate.
b. Leaky check valve seat.
1. Remove valve mechanism as outlined.
2. Mark distributor housing, with chalk, at number
one and number six cylinder position (plug wire)
then disconnect plug wires at spark plugs and coil
and remove distributor cap and plug wire assembly.
3. Crank engine until distributor rotor points to
number one position, then disconnect distributor
primary lead at coil and remove distributor.
4. Remove push rod covers (discard gaskets).
5. Remove valve lifters.
NOTE: Place valve lifters in a rack so that
they may be reinstalled in the same location.
Installation
1. Install valve lifters.
NOTE: Whenever new valve lifters are being
installed, coat foot of valve lifters with
“Molykote” or its equivalent.
2. Install push rod covers, using new gaskets, and
torque to specifications.
3. Install distributor, positioning rotor to number one
cylinder position, then connect primary lead at coil.
4. Install and adjust valve mechanism as outlined.
5. Adjust ignition timing and carburetor idle speed.
Valve Stem Oil Seal and/or Valve Spring
Replacement
1. Remove rocker arm cover as outlined.
2. Remove spark plug, rocker arm and push rod on
the cylinder(s) to be serviced.
3. Install air line adapter Tool J-23590 to spark plug
port and apply compressed air to hold the valves in
place.
4. Using Tool J-5892 to compress the valve spring,
LIGHT DUTY TRUCK SERVICE MANUAL
6 -2 8 ENGINE
5.
6.
7.
8.
9.
remove the valve locks, valve cap, valve shield and
valve spring and damper (fig. 7L).
Remove the valve stem oil seal.
To replace, set the valve spring and damper, valve
shield and valve cap in place. Compress the spring
with Tool J-5892 and install oil seal in the lower
groove of the stem, making sure the seal is flat and
not twisted.
NOTE: A light coat of oil on the seal will
help prevent twisting.
Install the valve locks and release the compressor
tool, making sure the locks seat properly in the
upper groove of the valve stem.
NOTE: Grease may be used to hold the locks
in place while releasing the compressor tool.
Install spark plug and torque to specifications.
Install and adjust valve mechanism as outlined.
Cylinder Head Assemblies
Removal
1.
2.
3.
4.
5.
6.
7.
8.
Remove manifold assembly as outlined.
Remove valve mechanism as outlined.
Drain cooling system (block).
Remove fuel and vacuum line from retaining clip
at water outlet then disconnect wires from
temperature sending units.
Disconnect air injection hose at check valve.
Disconnect radiator upper hose at water outlet
housing and battery ground strap at cylinder head.
Remove coil.
Remove cylinder head bolts, cylinder head and
gasket. Place cylinder head on two blocks of wood
to prevent damage.
Installation
CAUTIO N: The gasket surfaces on both the
head and the block must be clean of any
foreign matter and free of nicks or heavy
scratches. Cylinder bolt threads in the block
and threads on the cylinder head bolt must be
cleaned. (Dirt will affect bolt torque). Do not
use gasket sealer on composition steel asbestos
gaskets.
1. Place the gasket in position over the dowel pins
with the bead up.
2. Carefully guide cylinder head into place over dowel
pins and gasket.
3. Coat threads of cylinder head bolts with sealing
compound and install finger tight.
4. Tighten cylinder head bolts a little at a time in the
sequence shown on the torque sequence chart until
the specified torque is reached.
5. Connect air injection hose at check valve.
6 . Install coil.
7. Connect radiator upper hose and engine ground
strap.
8 . Connect temperature sending unit wires and install
fuel and vacuum lines in clip at water outlet.
9. Fill cooling system.
10. Install manifold assembly as outlined.
11. Install and adjust valve mechanism as outlined.
12. Install and torque rocker arm cover.
Oil Pan
Removal
1. Disconnect battery ground cable.
2. Raise vehicle on a hoist and disconnect starter at
engine block - leave electrical connections intact
and position starter out of way.
3. On G Series vehicles, remove bolts securing engine
mounts to crossmember brackets - then, using a
suitable jack with a flat piece of wood to protect oil
pan, raise engine sufficiently to insert 2” x 4” wood
block between engine mounts and crossmember
brackets (fig. 8 L).
4. Drain engine oil and remove flywheel (convertor)
cover.
5. Remove oil pan bolts and withdraw oil pan from
engine.
Installation
Fig. 7L—Compressing Valve Spring
1. Discard old gaskets and seals, thoroughly clean all
gasket sealing surfaces.
2. Install new rear seal in rear main bearing cap.
LIGHT DUTY TRUCK SERVICE MANUAL
EN GINE
6-29
Fig. 8L—Engine Blocked for Oil Pan Removal
3. Install new front seal on crankcase front cover
pressing, tips into holes provided in cover.
4. Install new side gaskets on cylinder block (fig. 9L).
NOTE: DO NOT USE SEALER.
5. Position oil pan to block, making sure that seals
and gaskets remain in place, install and torque pan
screws to specifications.
6 . On G Series vehicles, raise engine as outlined above
and remove blocks used to support engine.
7. On G Series vehicles, lower engine, install and
torque mount-to-crossmember bracket bolts.
8 . Install starter and flywheel (convertor) cover.
9. Fill engine with specified quantity of oil, then start
engine and check for leaks.
Oil Pump
Removal
1. Remove oil pan as outlined.
2. Remove two flange mounting bolts, pickup pipe
bolt, then remove pump and screen as an assembly.
Installation
1. Align oil pump drive shafts to match with
distributor tang, then install oil pump to block
positioning flange over distributor lower bushing.
Use no gasket.
NOTE: Oil pump should slide easily into
place, if not, remove and reposition slot to
align with distributor tang.
2. Install oil pan as outlined.
Fig. 9L—Oil Pan Gasket and Seal Location
Oil Seal (Rear Main)
Replacement
NOTE: Always replace the upper and lower
seal as a unit. Install seal with lip facing front
of engine.
The rear main bearing oil seal can be replaced (both
halves) without removal of the crankshaft. Extreme care
should be exercised when installing this seal to protect
the sealing bead located in the channel on the outside
diameter of the seal. An installation tool (fig. 10L) can
be used to protect the seal bead when positioning seal as
follows:
1. With the oil pan and oil pump removed, remove
the rear main bearing cap.
2. Remove oil seal from the bearing cap by prying
from the bottom with a small screw driver (fig.
1 1 L).
3. To remove the upper half of the seal, use a small
hammer to tap a brass pin punch on one end of
seal until it protrudes far enough to be removed
with pliers (fig. 12L).
4. Clean all sealant and foreign material from
cylinder case bearing cap and crankshaft, using a
non-abrasive cleaner.
5. Inspect components for nicks, scratches, burrs and
machining defects at all sealing surfaces, case
assembly and crankshaft.
LIGHT DUTY TRUCK SERVICE MANUAL
6 30 ENGINE
6 . Coat seal lips and seal bead with light engine oil —
keep oil off seal mating ends.
7. Position tip of tool between crankshaft and seal seat
in cylinder case.
8 . Position seal between crankshaft and tip of tool so
that seal bead contacts tip of tool.
NOTE: Make sure that oil-seal lip is
positioned toward front of engine (fig. 13L).
9. Roll seal around crankshaft using tool as
a “shoe-horn” to protect seal bead from
sharp corner of seal seat surface in
cylinder case.
CAU TIO N: Installation tool must remain in
position until seal is properly positioned with
both endsflush with block.
10. Remove tool, being careful not to withdraw seal.
11. Install seal half in bearing cap, again using tool as
a “shoe-horn”, feeding seal into cap using light
pressure with thumb and finger.
12. Install bearing cap to case with sealant applied to
the cap-to-case interface, being careful to keep
sealant off the seal split line (fig. 14L).
Fig. 11L—Removing Oil Seal (Lower Half) Typical
13. Install the rear main bearing cap (with new seal)
and torque to specifications.
Torsional Damper
Removal
1. Drain radiator and disconnect radiator hoses at
radiator.
2. Remove radiator core, as outlined in Section 13.
3. Remove fan belt and (if so equipped) accessory
drive pulley and belt. If so equipped, remove
retaining bolt.
4. Install Tool J-23523 to damper and turn puller
screw to remove damper (fig. 15L). Remove tool
from damper.
Installation
CAUTIO N: The inertia weight section of the
torsional damper is assembled to the hub with a
rubber type material. The installation proce&shy;
dures (with proper tool) must be followed or
movement of the inertial weight section on the
hub will destroy the tuning of the torsional
damper.
1. Coat front seal contact area (on damper) with
engine oil.
2. Install torsional damper as follows:
DRIVE ON TYPE (Without retaining bolt)
a. Attach damper installer Tool J-22197 to damper.
Tighten fingers of tool to prevent inertia weight
from moving (fig. 16L).
b. Position damper on crankshaft and drive into
position, using J-5590, until it bottoms against
crankshaft gear (fig. 16L). Remove installer tool.
PULL ON TYPE (With retaining bolt)
a. Install 7/16 threaded end of Tool J-23523 into
crankshaft.
Fig. 12L—Removing Oil Seal (Upper Half) Typical
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
6-31
Fig. 15L—Removing Torsional Damper
Fig. 13L—Crankshaft Oil Seal (Rear Main)
CAUTION: Install tool in crankshaft so that at
least 1/2&quot; of thread engagement is obtained.
3.
4.
5.
6.
7.
b. Position damper on crankshaft, aligning
damper with key on crankshaft.
c. Install plate, thrust bearing and nut to complete
tool installation.
d. Pull damper into position as shown in Figure
11L.
e. Remove tool from crankshaft.
Install fan belt and adjust, using strand tension
gauge.
If so equipped, install accessory drive pulley and
belt.
Install radiator core as outlined in Section 13.
Connect radiator hoses.
Fill cooling system and check for leaks.
APPLY
SEALANT
TO SHADED
AREAS ONLY
Fig. 14L—Sealing Bearing Cap
Fig. 16L—Installing Torsional Damper (Drive on
Type)
Crankcase Front Cover
Removal
1. Remove torsional damper as outlined.
2. Remove the two, oil pan-to-front cover attaching
screws.
3. Remove the front cover-to-block attaching screws.
4. Pull the cover slightly forward only enough to
permit cutting of oil pan front seal.
5. Using a sharp knife or other suitable cutting tool,
cut oil pan front seal flush with cylinder block at
both sides of cover (fig. 18L).
6 . Remove front cover and attached portion of oil pan
front seal. Remove front cover gasket.
Installation
1. Clean gasket surfaces on block and crankcase front
cover.
LIGHT DUTY TRUCK SERVICE MANUAL
6 -3 2 ENGINE
Fig. 18L—Cutting Tabs on Oil Pan Front Seal
Fig. 17L—installing Torsional Damper (Pull on Type)
2. Cut tabs from the new oil pan front seal (fig. 19L)
use a sharp instrument to ensure a clean cut.
3. Install seal to front cover, pressing tips into holes
provided in cover.
4. Coat the gasket with gasket sealer and place in
position on cover.
5. Apply a 1/8 inch bead of silicone rubber sealer part
#1051435 (or equivalent) to the joint formed at the
oil pan and cylinder block (fig. 20L).
6 . Install centering tool J-23042 in crankcase front
cover seal (fig. 21 L).
NOTE: It is important that centering tool be
used to align crankcase front cover so that
torsional damper installation will not damage
seal and so that seal is positioned evenly
around balancer.
7. Install crankcase front cover to block. Install and
paratially tighten the two, oil pan-to-front cover
screws.
8 Install the front cover-to-block attaching screws.
9. Remove centering Tool J-23042 and torque all cover
attaching screws to specifications.
10. Install torsional damper as outlined.
Fig. 20L—Applying Front Cover Sealer
Oil Seal (Front Cover)
Replacement
With Cover Removed
1. With cover removed, pry seal out of cover from the
front with a large screw driver being careful not to
distort cover.
.
CUT THIS PORTION
FROM NEW SEAL
Fig. 19L—Oil Pan Front Seal Modification
Fig. 21L—Centering Tool (J-23042) In Cover
LIGHT DUTY TRUCK SERVICE MANUAL
EN G IN E
2. Install new seal so that open end of the seal is
toward the inside of cover, and drive it into
position with Tool J-23042 (fig. 22L).
Camshaft
Measuring Lobe Lift
CAU TIO N: Support cover at sealing area.
(Tool J-971 may be used as support).
Without Cover Removed
1. With crankshaft pulley and hub or damper
removed, pry old seal out of cover from the front
with a large screw driver, being careful not to
damage the seal surface on the crankshaft.
2. Install new seal so that open end of seal is toward
the inside of cover and drive it into position with
Tool J-23042 (fig. 23L).
6-33
1.
2.
3.
4.
NOTE: Procedure is similar to that used for
checking valve timing. If improper valve
operation is indicated, measure the lift of
each push rod in consecutive order and
record the readings.
Remove valve mechanism as outlined.
Position indicator with ball socket adapter (Tool
J-8520) on push rod (fig. 24L).
Rotate the crankshaft slowly in the direction of
rotation until the lifter is on the heel of the cam
lobe. At this point, the push rod will be in its lowest
position.
Set dial indicator on zero, then rotate the
Fig. 22L—
-Installing Oil Seal (Cover Removed)
Fig. 24L—Measuring Camshaft Lobe Lift
Fig. 23L—installing Oil Seal (Cover Installed)
(Typical)
Fig. 25L—Timing Gear Alignment Marks
LIGHT DUTY TRUCK SERVICE MANUAL
6 -3 4 ENGINE
crankshaft slowly, or attach an auxiliary starter
switch and “bump” the engine over, until the push
rod is in the fully raised position.
CAUTIO N: Whenever the engine is cranked
remotely at the starter, with a special jumper
cable or other means, the distributor primary
lead must be disconnected from the negative
post on the coil.
5. Compare the total lift recorded from the dial
indicator with specifications.
6 . Continue to rotate the crankshaft until the indicator
reads zero. This will be a check on the accuracy of
the original indicator reading.
7. If camshaft readings for all lobes are within
specifications, remove dial indicator assembly.
8 . Install and adjust valve mechanism as outlined.
Removal
1.
2.
3.
4.
5.
Remove valve lifters as outlined.
Remove crankcase front cover as outlined.
Remove grille as outlined in Section 13.
Remove fuel pump as outlined in Section 6 M.
Align timing gear marks then remove the two
camshaft thrust plates screws by working through
holes in the camshaft gear (fig. 25L).
6 . Remove the camshaft and gear assembly by pulling
it out through the front of the block.
NOTE: Support camshaft carefully when
removing so as not to damage camshaft
bearings.
Fig. 26L—Checking Camshaft Gear Runout
Fig. 27L—Checking Timing Gear Backlash
Installation
1. Install the camshaft and gear assembly in the
engine block, being careful not to damage camshaft
bearings or camshaft.
2. Turn crankshaft and camshaft so that the valve
timing marks on the gear teeth will line up (fig.
25L). Push camshaft into position. Install camshaft
thrust plate to block screws and torque to
specifications.
3. Check camshaft and crankshaft gear runout with a
dial indicator (fig. 26L). The camshaft gear run out
should not exceed .004&quot; and the crankshaft gear
run out should not exceed .003&quot;.
4. If gear run out is excessive, the gear will have to be
removed and any burrs cleaned from the shaft or
the gear will have to be replaced.
5. Check the backlash between the timing gear teeth
with a dial indicator (fig. 27L). The backlash should
be not less than .004&quot; nor more than .006&quot;.
6 . Install fuel pump as outlined in Section 6 M.
7. Install grille as outlined in Section 13.
Fig. 28L—Removing Crankshaft Gear
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
6-35
Fig. 29L—Installing Crankshaft Gear
8. Install crankcase front cover as outlined.
9. Install valve lifters as outlined.
Timing Gears
Replacement
With camshaft removed, crankshaft gear may be
removed using Tool J-8105 (fig. 28L). To install
crankshaft gear use Tool J-5590 (fig. 29L). For camshaft
gear replacement, refer to “Camshaft Disassembly” in
the Overhaul Manual.
Flywheel
Removal
(All Except 2 9 2 cu. in. Engines)
1. Remove transmission and/or clutch housing and
clutch from engine.
2. Remove flywheel retaining bolts and remove
flywheel.
(2 9 2 cu. in. Engines)
1. Remove transmission and/or clutch housing and
clutch from engine.
2. Mark relationship of flywheel and crankshaft so
that dowel holes can be aligned in their original
positions on assembly.
CONVERTER
BOLT AREA - J |
DEPRESSED
GEAR
WELDS
TRANS.^
SYNCHROMESH
AUTOMATIC
Fig. 30L—Flywheel Installation (Typical)
Fig. 31L—Reaming Flywheel Dowel Pin Holes
3. Remove engine oil pan and rear main bearing cap.
4. Remove flywheel retaining bolts and drive crank&shy;
shaft dowels out of flywheel and crankshaft. Rotate
crankshaft as necessary so dowels clear cylinder
block.
5. Remove flywheel and discard used dowel pins.
Installation
(All Except 2 9 2 cu. in. Engines)
1. Clean the mating surfaces of flywheel and
crankshaft to make certain there are no burrs.
2. Install flywheel on crankshaft and position to align
dowel hole of crankshaft flange and flywheel (fig.
30L).
3. Install flywheel retaining bolts and torque to
specifications.
(292 cu. in. Engine)
1. Clean the mating surfaces of flywheel and
crankshaft to make certain there are no burrs.
2. Install flywheel on crankshaft and position to align
dowel holes of crankshaft flange and flywheel.
3. Install flywheel retaining bolts and torque to
specifications.
NOTE: The interference fit dowel pins used
on 292 cu. in. engines must be replaced with
an oversize dowel pin when installing the
flywheel.
4. When installing the original flywheel, ream the
dowel pin holes with Tool J-22808-2. When
installing a new flywheel, first ream the dowel pin
LIGHT DUTY TRUCK SERVICE MANUAL
6 3 6 E N G IN E
holes with Tool J-22808-2 and then finish reaming
them with Tool J-22808-1 (fig. 31L).
5. Install oversize dowel pins flush with flywheel
retaining bolt surface.
6. Install rear main bearing cap and torque bolts to
specifications. Install oil pan with new gaskets and
seals. Torque oil pan retaining screws to
specifications.
Engine Mounts
Engine mounts (fig. 32L-38L) are the non-adjustable
type and seldom require service. Broken or deteriorated
mounts should be replaced immediately, because of the
added strain placed on other mounts and drive line
components.
3.
4.
5.
6.
7.
Checking Engine Mounts
Front Mount
Raise the engine to remove weight from the mounts and
to place a slight tension in the rubber. Observe both
mounts while raising engine. If an engine mount
exhibits:
a. Hard rubber surface covered with heat check
cracks;
b. Rubber separated from a metal plate of the
mount; or
c. Rubber split through center.
Replace the mount, if there is relative movement
between a metal plate of the mount and its attaching
points, lower the engine on the mounts and tighten the
screws or nuts attaching the mount to the engine, frame,
or bracket.
Rear Mount
Raise the vehicle on a hoist. Push up and pull down on
the transmission tailshaft while observing the transmis&shy;
sion mount. If the rubber separates from the metal plate
of the mount or if the tailshaft moves up but not down
(mount bottomed out) replace the mount. If there is
relative movement betwen a metal plate of the mount
and its attaching point, tighten the screws or nuts
attaching the mount to the transmission or crossmember.
Front Mount Replacement
C, K and P Series
1.
2.
3.
4.
5.
Remove frame bracket to mount bolt.
Raise engine enough to clear mount.
Remove mount and install new mount.
Install new mount and torque bolts to specifications.
Lower engine then install frame bracket to mount
bolt and torque to specifications.
G Series
1. Raise vehicle on hoist.
2. On manual transmission equipped vehicles.
8.
a. Disconnect clutch rod at outboard lever on
clutch cross shaft.
b. Remove the two bolts securing clutch cross shaft
bracket to frame side rail, and position clutch
linkage away from engine mount.
Remove mount-to-bracket through-bolt.
Raise engine sufficiently to clear mount. Remove
bolts securing mount to frame bracket.
Install new mount to frame bracket, and torque
bolts to specifications.
Lower engine to align mount with engine bracket.
Install through bolt and torque to specifications.
On manual transmission equipped vehicles.
a. Position clutch cross shaft between frame side
rail and ball stud on engine bracket. Install and
torque frame bolts.
b. Connect clutch rod at outboard lever on clutch
cross shaft.
Lower vehicle on hoist and check operation of
clutch.
Rear Mount Replacement
C, K and P Series
1. Raise and support vehicle.
2. Bend mount bolt french lock tabs away from bolt
head, then remove mount bolts, lower mount and
spacer.
3. Raise engine enough to clear upper mount
assembly and remove upper mount from frame
member.
NOTE: On models using a propeller shaft
brake of any type, it is necessary to remove
screws from transmission hole cover to allow
the engine to raise because of the limited
clearance between the brake and transmis&shy;
sion hole cover.
4. Place new upper mount in place on frame member,
then lower engine to within 1 /4 inch of mount.
5. Align mount so that guide dowel enters hole in
mount, install bolt through french lock, lower
mount and spacer, then install bolt up through
frame, upper mount and thread into engine bell
housing loosely.
6. Lower engine completely and tighten mount bolt,
then bend tabs of french lock to lock the bolt in
place.
G Series
1. Raise vehicle on hoist and support transmission so
as not to interfere with support crossmember
removal.
2. Remove bolts securing rear mount to support
crossmember.
3. Remove support crossmember retaining bolts from
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
underbody cross rail and withdraw support from
vehicle.
4. Remove bolts securing mount to transmission
extension.
5. Install new rear mount and torque bolts to
specifications.
6-37
6. Position support crossmember to cross rail, install
bolts then loosely install crossmember-to-mount
retaining bolts.
7. Remove support from rear of transmission, torque
remaining bolts to specifications and lower vehicle
on hoist.
LIGHT DUTY TRUCK SERVICE MANUAL
6 3 8 E N G IN E
250 CU. IN. ENGINE
4 i LEFT &amp; RIGHT MOUNT
&amp; FRAME BRACKET
292 CU. IN. ENGINE
LEFT MOUNT &amp;
FRAME BRACKEET
0
ENGINE BRACKET
ALL P SERIES
WITH L-6 ENGINE
292 CU. IN. ENGINE
RIGHT FRAME
BRACKET &amp; MOUNT
Fig. 33L—P Series Engine Front Mount
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6-39
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6 - 4 0 E N G IN E
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6-41
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6-42
ENG INE
LIGHT
DUTY TRUCK
SERVICE MANUAL
Fig. 37L—K Series Engine Front Mount
E N G IN E
6-43
REAR MOUNT
FRONT MOUNT
Fig. 38L—G Series Engine Mounts
LIGHT DUTY TRUCK SERVICE MANUAL
ENGINE 6-44
ENGINE MECHANICAL
V-8 ENGINES
INDEX
General Description...........................................................
Component Replacement and Adjustment.................
Engine Assembly................................................................
Removal..............................................................................
Installation.........................................................................
Intake M anifold.................................................................
Removal..............................................................................
Installation.........................................................................
Exhaust Manifold...............................................................
Removal..............................................................................
Installation.........................................................................
Rocker Arm Cover...........................................................
Removal............................................................ .................
Installation.........................................................................
Valve Mechanism..............................................................
Removal..............................................................................
Installation and Adjustment........................................
Valve Lifters.......................................................................
Locating Noisy Lifters.................................................
Removal..............................................................................
Installation.........................................................................
Valve Stem Oil Seal and/or Valve Spring..............
Replacement......................................................................
Cylinder Head Assembly................................................
Removal..............................................................................
Installation.........................................................................
Oil P an .................................................................................
6-44
6-44
6-44
6-44
6-47
6-49
6-49
6-50
6-50
6-50
6-50
6-50
6-50
6-51
6-51
6-51
6-51
6-51
6-51
6-52
6-52
6-52
6-52
6-52
6-52
6-53
6-53
Removal..............................................................................
Installation.........................................................................
Oil Pump..............................................................................
Removal..............................................................................
Installation.........................................................................
Oil Seal (Rear M ain)......................................................
Replacement......................................................................
Torsional Damper.............................................................
Removal..............................................................................
Installation.........................................................................
Crankcase Front Cover...................................................
Removal..............................................................................
Installation.........................................................................
Oil Seal (Front Cover)....................................................
Replacement......................................................................
Timing Chain and/or Sprockets..................................
Replacement......................................................................
Camshaft..............................................................................
Measuring Lobe L ift.....................................................
Removal..............................................................................
Installation.........................................................................
Flywheel................................................................................
Removal..............................................................................
Installation.........................................................................
Engine M ounts...................................................................
Checking Engine Mounts..............................................
Replacement (Front)......................................................
Replacement (Rear)........................................................
6-53
6-53
6-54
6-54
6-54
6-54
6-54
6-55
6-55
6-55
6-55
6-55
6-56
6-57
6-57
6-57
6-57
6-58
6-58
6-59
6-59
6-60
6-60
6-60
6-60
6-60
6-60
6-61
GENERAL DESCRIPTION
The V8 engines covered in this section are the 307, 350,
and 454 cu. in. engines used in 10-30 Series truck
vehicles. In order to avoid repetition and to identify the
engines involved in a particular procedure, the 307 and
350 cu. in. V8 engines are identified as “Small V8’s” .
The 454 cu. in. engine is identified as “Mark IV V8” .
This section covers the removal and installation of
engine assemblies; the removal, installation and
adjustment of some sub-assemblies and replacement of
some components. For service to all components and
sub-assemblies (after removal) and removal of some
sub-assemblies, refer to Section 6 of the Overhaul
Manual.
Because of the interchangeability and similarity of many
engines, engine sub-assemblies and parts regardless of
which truck vehicle they are used in, typical illustrations
and procedures are used (except where specific
illustrations or procedures are necessary to clarify the
operation). Although illustrations showing bench opera&shy;
tions are used, most single operations, when not part of a
general overhaul, should be performed (if practical) with
the engine in the vehicle.
C O M P O N E N T REPLACEMENT A N D ADJUSTMENT
Engine Assembly
3. Perform the following preliminary operations:
Removal
• Remove the hood as outlined in Section 11.
C, K and P Series
• Remove the radiator and shroud as outlined in
1. Disconnect battery cables and drain cooling system.
Section 13.
2. Remove the air cleaner.
LIGHT DUTY TRUCK SERVICE MANUAL
ENGIN E
4. Disconnect wires at:
• TCS Solenoid
• Starter Solenoid
• Delcotron
• Temperature Switch
• Oil Pressure Switch
• Coil
5. Disconnect:
• Accelerator linkage at manifold bellcrank
• Fuel line (from tank) at fuel pump.
• Heater hoses at engine connection.
• Oil pressure gauge line (if so equipped).
• Vacuum or air lines at engine (as required).
• Power steering pump with hoses attached and lay
aside (if so equipped).
• Ground straps at engine.
• Exhaust pipe at manifold.
• TCS switch at transmission.
NOTE: Hang exhaust pipe at frame with
wire.
6.
7.
8.
9.
Remove fan and pulley as outlined in Section 6K.
Remove clutch cross-shaft.
Perform the following operations:
Attach lifting device to engine lift brackets ana
take weight off engine mounts.
ON ALL SERIES EXCEPT CE 10-20-30:
• Support transmission and disconnect from
engine.
• Disconnect speedometer cable at transmission.
• Disconnect shift linkage at transmission.
• Disconnect clutch linkage (as required).
• Remove engine mount bolts.
10. Remove engine from vehicle as follows:
CAUTION: Check often during engine removal
to be sure all necessary disconnects have been
made.
ON CE 10-20-30 SERIES:
6-45
• On vehicles with automatic or four speed
transmissions, remove rear mount crossmember.
• Raise engine and transmission assembly and pul!
forward until removed.
ON KE 10-20 SERIES:
• Raise engine and pull forward until disconnected
from tranmission.
• Continue to raise engine until removed from
vehicle.
11. If engine is to be mounted in an engine stand
perform the following:
ON CE 10-20-30 SERIES:
• Remove synchromesh tranmission and clutch (if
so equipped).
a. Remove clutch housing rear cover bolts.
b. Remove bolts attaching the clutch housing to
engine block then remove transmission and
clutch housing as a unit.
NOTE: Support the transmission as the last
mounting bolt is removed and as it is being
pulled away from the engine, to prevent
damage to clutch disc.
c. Remove starter and clutch housing rear
cover.
d. Loosen clutch mounting bolts a turn at a
time (to prevent distortion of clutch cover)
until the spring pressure is released. Remove
all bolts, clutch disc and pressure plate
assembly.
• Remove automatic transmission (if so equipped).
a. Lower engine, secured by the hoist, and
support engine on blocks.
b. Remove starter and converter housing under
pan.
c. Remove flywheel-to-converter attaching
bolts.
d. Support transmission on blocks.
e. Disconnect throttle linkage and vacuum
modulator line.
f. Remove tranmission-to-engine mounting
bolts.
g. With the hoist attached, remove blocks from
the engine only and glowly guide the engine
from the transmission.
ON ALL SERIES EXCEPT CE 10-20-30:
• Remove clutch housing.
• Loosen clutch mounting bolts a turn at a time (to
prevent distortion of clutch cover) until the
spring pressure is released. Remove all bolts,
clutch disc and pressure plate assembly.
12. Mount engine in engine stand and remove lifting
device and lifting adapter.
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 4 6 E N G IN E
G Series
1. Remove engine cover and position it out of way.
2. Disconnect battery ground cable at engine block
and at battery.
3. Drain cooling system and disconnect heater hoses
at engine; disconnect radiator hoses at radiator.
4. Disconnect automatic transmission cooler lines at
radiator; remove radiator shroud and radiator.
5. Remove carburetor air cleaner and remove engine
oil filler tube.
6 . Remove Delcotron and support bracket - position
assembly out of way on left frame rail.
7. Disconnect oil pressure gauge if so equipped.
8. Disconnect engine wiring harness at dash panel
junction block.
9. Disconnect accelerator linkage at dash panel
mounted bell crank.
Disconnect TCS system electrical leads - remove
harness from clips and position it to one side.
11. Disconnect Evaporation Control System lines at
rocker arm cover and at carburetor - position lines
to one side.
12. Disconnect power brake vacuum hose at rocker arm
tube-to-hose junction.
13. Raise vehicle on a hoist and disconnect:
Fuel line (from tank) at fuel pump.
Engine ground strap(s).
Steering idler arm at frame.
Steering pitman arm at steering gear as outlined
in Section 9.
Stabilizer shaft at frame brackets.
Battery positive cable at starter.
Shock absorbers at lower control arm.
Speedometer cable at transmission.
TCS switch at transmission-remove bell housing
mounted clip and position wiring to one side.
Transmission at crossmember.
Exhaust crossover at manifolds and at muffler.
14. Remove propeller shaft as outlined in Section 4 install plug in transmission extension.
15. Disconnect clutch linkage and/or transmission
linkage and remove cross shaft as outlined in
Section 7.
16. Disconnect front brake pipe at equalizer tee,
disconnect rear brake pipe at left frame rail
mounted connector and at right frame rail mounted
connector (Fig. IV).
17. Remove transmission support frame-to-crossmember attaching nuts - do not remove bolts at this
time.
18. Remove the six (3 on each side) vertically driven
19.
20.
21.
22.
23.
front crossmember-to-frame attaching bolts (Fig.
2V).
Remove the four (2 on each side) frame-to-upper
control arm (inside) attaching bolts (Fig. 3V).
Lower the vehicle on hoist so that weight of vehicle
is on hoist but with wheels touching floor and
suspension at curb height.
Install wood block between oil pan and crossmem&shy;
ber to stabilize engine assembly (Fig. 4V).
Position floor jack under vehicle so that jack pad is
aligned under transmission and, using a block of
wood to protect transmission, support transmission
with jack (Fig. 5V).
Remove transmission support crossmember.
Fig. 2V—Crossmember-to-Frame Attaching Bolts
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
24. Remove the four (2 on each side) remaining
suspension-to-frame (outside) retaining bolts (Fig.
3V).
25. Raise vehicle slowly, leaving suspension and power
train on the floor, until sufficient clearance is
obtained for removing engine.
CAUTION: Check often when raising the
vehicle to make sure that all disconnects have
been made and that vehicle is positioned
properly on hoist.
26. Roll the power train and suspension assembly to the
work area and position jack stand under transmis&shy;
sion extension (Fig. 6V)-remove floor jack.
27. Place floor jack under suspension crossmember and
raise jack so that weight of assembly is supported
on jack pad, (Fig. 4V).
28. Attach lifting device to support engine, remove
engine mount through bolts and remove engine
assembly from crossmember.
647
29. Remove synchromesh transmission and clutch (if so
equipped).
a. Remove clutch housing rear cover bolts.
b. Remove bolts attaching the clutch housing to
engine block, then remove transmission clutch
housing as a unit.
NOTE: Support the transmission as the last
mounting bolt is removed and as it is being
pulled away from the engine, to prevent
damage to clutch disc.
c. Remove starter and clutch housing rear cover.
d. Loosen clutch mounting bolts a turn at a time
(to prevent distortion of clutch cover) until the
spring pressure is released. Remove all bolts,
clutch disc and pressure plate assembly.
30. Remove automatic transmission (if so equipped).
a. Lower engine secured by the hoist, and support
engine on blocks.
b. Remove starter and converter housing
underpan.
c. Remove flywheel-to-converter attaching bolts.
d. Support transmission on blocks.
e. Disconnect throttle linkage and detent cable on
Turbo Hydra-Matic.
f. Remove transmission-to-engine mounting bolts.
g. With the hoist attached, remove blocks from the
engine only and slowly guide the engine away
from the transmission.
Installation
1. If engine was mounted in an engine stand, attach
lifting adapter to engine then using lifting device,
remove engine from stand and perform the
following:
Fig. 4V—Stabilizing Power Train
Fig. 5V—Floor Jack Location Under Transmission
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 4 8 E N G IN E
3.
4.
5.
6.
Fig. 6V—Supporting Power Train
ON CE 10-20-30:
• Install synchromesh tranmission and clutch (if so
equipped).
a. Install the clutch assembly on flywheel as
outlined in Section 7.
b. Install clutch housing rear cover and starter.
c. Install the tranmission and clutch housing as
outlined in Section 7.
d. Install clutch housing rear cover bolts and
torque to specifications.
• Install automatic tranmission (if so equipped).
a. Position engine adjacent to the transmission
and align the converter with the flywheel.
b. Bolt transmission to engine then raise engine
and transmission assembly and install
flywheel to converter bolts.
c. Install converter housing underpan and
starter.
d. Connect throttle linkage and vacuum modu&shy;
lator line.
ON ALL SERIES EXCEPT CE 10-20-30:
• Install clutch assembly and clutch housing as
outlined in Section 7.
2. Install engine in vehicle as follows:
ON ALL SERIES EXCEPT CE 10-20-30:
• Install engine and lower until transmission lines
up with clutch.
• Push engine rearward and rotate crankshaft until
transmission shaft and clutch engage.
• Install the engine mount bolts and torque to
specifications.
• Connect transmission to engine.
7.
8.
9.
ON CE 10-20-30 SERIES:
• Lower engine and transmission assembly and
push rearward until engine mounts line up.
• On vehicles with automatic or four speed
transmissions, install rear mount crossmember.
• Install the engine mount bolts and torque to
specifications.
• Install the propeller shaft as outlined in Section
4.
ON ALL SERIES:
• Remove the lifting device from engine lift
brackets.
Connect transmission linkage (as required).
Install clutch cross-shaft.
Install fan and pulley as outlined in Section 6K.
Connect:
• Exhaust pipe at manifold.
• Power steering pump (as required).
• Vacuum lines at engine (as required).
• Oil pressure gauge line (as required).
• Heater hoses at engine connection.
• Fuel line at fuel pump.
• Choke cable at carburetor.
• Accelerator linkage at manifold bellcrank.
• TCS switch at transmission.
Connect wires at:
• Coil
• Oil Pressure Switch
• Temperature Switch
• Delcotron
• Starter Solenoid
• CEC Solenoid
Complete installations as follows:
• Install the radiator and shroud as outlined in
Section 13.
• Install the hood as outlined in Section 11.
Install the air cleaner, connect battery cables, fill
cooling system and crankcase then start engine and
check for leaks.
G Series
1. If engine was mounted in an engine stand, attach
lifting adapter to engine, then, using lifting device,
remove engine from stand and perform the
following:
• Install manual transmission and clutch (if so
equipped).
a. Install the clutch assembly on flywheel as
outlined in Section 7.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
b. Install clutch housing rear cover and starter.
c. Install the transmission and clutch housing as
outlined in Section 7.
d. Install clutch housing rear cover bolts and
torque to specifications.
• Install automatic transmission (if so equipped).
a. Position engine adjacent to the transmission and
align converter with the flywheel.
b. Bolt transmission to engine then raise engine
and transmission assembly and install flywheel
to converter bolts.
c. Install converter housing underpan and starter.
d. Connect throttle valve linkage and vacuum
modulator. Connect detent cable on Turbo
Hydra-Matic.
Raise engine and align mounts on engine with
brackets on crossmember - install engine mount
through bolts.
Place wood block between oil pan and crossmember
to stabilize power train.
Remove floor jack from under crossmember and
position jack pad under transmission assembly,
using wood block at jack pad to protect
transmission.
Remove the engine lifting device and roll power
train and suspension assembly under vehicle so that
crossmember is aligned with frame.
Slowly lower the vehicle, checking often to assure
that engine components do not interfere with
vehicle as it is being lowered, until suspension-toframe attaching bolt holes are aligned.
Install and securely tighten suspension-to-frame
attaching bolts.
Install transmission support crossmember and
remove floor jack from beneath the transmission.
Remove block of wood from between oil pan and
crossmember.
Raise vehicle on the hoist and install the remaining
suspension-to-frame attaching bolts - torque bolts
to specifications. Torque transmission to-crossmember and crossmember-toframe bolts to
specifications.
Install propeller shaft as outlined in Section 4.
Connect rear brake pipe at right frame rail
connector; connect front brake pipe at equalizer tee
and connect rear brake pipe at left frame rail
connector.
Install cross shaft and connect clutch linkage and/
or transmission linkage as outlined in Section 7.
Connect the following items:
• Fuel line (from tank) at fuel pump.
• Engine ground strap(s).
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
6-49
• Steering idler arm at frame.
• Steering pitman arm at steering gear - torque
nut to specifications.
• Stabilizer shaft at frame brackets.
• Battery positive cable at starter.
• Shock absorbers at lower control arm.
• Speedometer cable at transmission.
• TCS switch at transmission - install TCS wire to
clip at transmission/clutch housing.
• Exhaust crossover at muffler and at manifolds.
Lower vehicle on hoist.
Connect power brake vacuum hose at tube-to-hose
junction.
Connect Evaporation Control System lines at rocker
arm cover and carburetor.
Connect TCS system electrical leads at valve and at
temperature switch - position harness in rocker arm
cover clips.
Install Delcotron and support assembly.
Connect accelerator linkage at dash mounted bell
crank.
Install carburetor air cleaner and oil filler tube connect oil pressure gauge line if so equpped.
Connect engine wiring harness at dash panel
junction block.
Install radiator and fan shroud, connect radiator
and heater hoses, install automatic transmission
cooler lines and fill cooling system.
Install engine cover.
Connect battery ground cable at engine block and
at battery.
Bleed front and rear brakes as outlined in Section
5.
Start engine, check and add engine coolant as
required and check engine for proper operation.
Intake Manifold
Removal
1. Drain radiator and remove air cleaner.
2. Disconnect:
• Battery cables at battery.
• Radiator upper hose and heater hose at
manifold.
• Water pump by-pass at water pump.
• Accelerator linkage at pedal lever.
• Fuel line and choke cable at carburetor.
• Crankcase ventilation lines (as required).
• Spark advance hose and governor line (if so
equipped) at distributor.
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 5 0 E N G IN E
3. Remove distributor cap and mark rotor position
with chalk, then remove distributor.
4. Remove (as required) oil filler bracket, air cleaner
bracket, air compressor and bracket, coil, accelera&shy;
tor return spring and bracket, and accelerator
bellcrank.
5. Remove manifold attaching bolts, then remove
manifold and carburetor as an assembly. Discard
gaskets and seals.
6. If manifold is to be replaced, transfer:
• Carburetor and carburetor mounting studs.
• Temperature sending unit.
• Water outlet and thermostat (use new gasket).
• Heater hose and water pump by-pass adapters.
• EGR Valve (use new gasket).
Installation
1. Clean gasket and seal surfaces on manifold, block,
and cylinder heads.
2. Install manifold seals on block and gaskets on
cylinder heads (fig. 7V). Use sealer at water
passages and where seals butt to gaskets.
3. Install manifold and torque bolts to specifications in
the sequence outlined on the torque sequence chart.
4. Install (if removed) oil filler bracket, air cleaner
bracket, air compressor and bracket, coil, accelera&shy;
tor return spring and bracket and accelerator
bellcrank.
5. Install distributor, positioning rotor at chalk mark,
then install distributor cap.
6. Connect:
REAR SEAL
GASKETS
• Spark advance hose and governor line (if so
equipped) at distributor.
• Crankcase ventilation lines (as required).
• Fuel line and choke cable at carburetor.
• Accelerator linkage at pedal lever.
• Water pump by-pass at water pump (use new
gasket).
• Battery cables at battery.
7. Adjust choke cable and accelerator linkage as
outlined.
8. Install air cleaner.
9. Fill with coolant, start engine, adjust ignition
timing and carburetor idle speed and check for
leaks.
Exhaust Manifold
Removal
1. On vehicles so equipped, remove carburetor heater.
2. On right exhaust manifold, disconnect and remove
Delcotron.
3. On “Mark IV V8” engines, remove spark plugs.
4. Disconnect exhaust pipe from manifold and hang
exhaust pipe from frame with wire.
5. Remove end bolts then remove center bolts and
remove manifold.
Installation
1. Clean mating surfaces on manifold and head, then
install manifold in position and install bolts (fingertight).
2. Torque manifold bolts to specifications in the
sequence shown on torque chart at end of section.
3. Connect exhaust pipe to manifold. Use new gasket
or packing.
4. On “Mark IV V8” engines, install spark plugs.
Torque plugs to specifications.
5. On right exhaust manifold, install and connect
Delcotron. Adjust belt as outlined in Engine Tune
Up.
6. On vehicles so equipped, install carburetor heater.
7. Start engine and check for leaks.
Rocker Arm Cover
Removal
FRONT SEAL
Fig. 7V—Intake Manifold Gasket and Seal Location
1. Remove air cleaner.
2. Disconnect crankcase ventilation hoses at rocker
arm covers.
3. Disconnect temperature wire from left rocker arm
clips.
4. On vehicles so equipped, remove carburetor heater
from right exhaust manifold.
LIGHT DUTY TRUCK SERVICE MANUAL
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5. Remove rocker arm cover.
CAUTION: Do not pry rocker arm cover loose.
Gaskets adhering to cylinder head and rocker
arm cover may be sheared by bumping end of
rocker arm cover rearward with palm o f hand
or a rubber mallet.
Installation
1. Clean gasket surfaces on cylinder head and rocker
arm cover with degreaser then, using a new gasket,
install rocker arm cover and torque to
specifications.
2. Install carburetor heater (if removed).
3. Connect temperature wire at clips on left rocker
arm cover.
4. Connect crankcase ventilation hoses (as required).
5. Install air cleaner, start engine and check for leaks.
Valve Mechanism
Removal
1. Remove rocker arm covers as outlined.
2. Remove rocker arm nuts, rocker arm balls, rocker
arms and push rods.
NOTE: Place rocker arms, rocker arm balls
and push rods in a rack so they may be
reinstalled in the same locations.
Installation and Adjustment
NOTE: Whenever new rocker arms and/or
rocker arm balls are being installed, coat
bearing surfaces of rocker arms and rocker
arm balls with “Molykote” or its equivalent.
1. Install push rods. Be sure push rods seat in lifter
socket.
2. Install rocker arms, rocker arm balls and rocker
arm nuts. Tighten rocker arm nuts until all lash is
eliminated.
3. Adjust valves when lifter is on base circle of
camshaft lobe as follows:
a. Crank engine until mark on torsional damper
lines up with center or “O ” mark on the timing
tab fastened to the crankcase front cover and
the engine is in the number 1 firing position.
This may be determined by placing fingers on
the number 1 valve as the mark on the damper
comes near the “O ” mark on the crankcase
front cover. If the valves are not moving, the
engine is in the number 1 firing position. If the
valves move as the mark comes up to the timing
tab, the engine is in number 6 firing position
and should be turned over one more time to
reach the number 1 position.
b. With the engine in the number 1 firing position
as determined above, the following valves may
be adjusted.
6-51
Exhaust — 1, 3, 4, 8
Intake — 1, 2, 5, 7
c. Back out adjusting nut until lash is felt at the
push rod then turn in adjusting nut until all lash
is removed. This can be determined by checking
push rod side play while turning adjusting nut
(fig. 8V). When play has been removed, turn
adjusting nut in one full additional turn (to
center lifter plunger).
d. Crank the engine one revolution until the
pointer “O” mark and torsional damper mark
are again in alignment. This is number 6 firing
position. With the engine in this position the
following valves may be adjusted.
Exhaust — 2, 5, 6, 7
Intake — 3, 4, 6, 8
4. Install rocker arm covers as outlined.
5. Adjust carburetor idle speed.
Valve Lifters
Hydraulic valve lifters very seldom require attention.
The lifters are extremely simple in design, readjustments
are not necessary, and servicing of the lifters requires
only that care and cleanliness be exercised in the
handling of parts.
Locating Noisy Lifters
Locate a noisy valve lifter by using a piece of garden
hose approximately four feet in length. Place one end of
the hose near the end of each intake and exhaust valve
with the other end of the hose to the ear. In this manner,
the sound is localized making it easy to determine which
lifter is at fault.
Another method is to place a finger on the face of the
valve spring retainer. If the lifter is not functioning
properly, a distinct shock will be felt when the valve
returns to its seat.
The general types of valve lifter noise are as follows:
1. Hard Rapping Noise—Usually caused by the
plunger becoming tight in the bore of the lifter
body to such an extent that the return spring can no
longer push the plunger back up to working
position. Probable causes are:
a. Excessive varnish or carbon deposit causing
abnormal stickiness.
b. Galling or “pick-up” between plunger and bore
of lifter body, usually caused by an abrasive
piece of dirt or metal wedging between plunger
and lifter body.
2. Moderate Rapping Noise—Probable causes are:
a. Excessively high leakdown rate.
b. Leaky check valve seat.
c. Improper adjustment.
3. General Noise Throughout the Valve Train—This
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 5 2 E N G IN E
will, in most cases, be caused by either insufficient
oil supply or improper adjustment.
4. Intermittent Clicking—Probable causes are:
a. A microscopic piece of dirt momentarily caught
between ball seat and check valve ball.
b. In rare cases, the ball itself may be out-of-round
or have a flat spot.
c. Improper adjustment.
In most cases where noise exists in one or more lifters all
lifter units should be removed, disassembled, cleaned in
a solvent, reassembled, and reinstalled in the engine. If
dirt, corrosion, carbon, etc. is shown to exist in one unit,
it more likely exists in all the units, thus it would only be
a matter of time before all lifters caused trouble.
Removal
1. Remove intake manifold as outlined.
2. Remove valve mechanism as outlined.
3. Remove valve lifters.
NOTE: Place valve lifters in a rack so that
they may be reinstalled in the same location.
Installation
1. Install valve lifters.
NOTE: Whenever new valve lifters are being
installed, coat foot of valve lifters with
“Molykote” or its equivalent.
2. Install intake manifold as outlined.
3. Install and adjust valve mechanism as
outlined.
Valve Stem Oil Seal and/or Valve Spring
Replacement
1. Remove rocker arm cover as outlined.
2. Remove spark plug, rocker arm and push rod on
the cylinder(s) to be serviced.
3. Install air line adapter Tool J-23590 to spark plug
port and apply compressed air to hold the valves in
place.
4. Using Tool J-5892 to compress the valve spring,
remove the valve locks, valve cap and valve spring
and damper (fig. 9V).
5. Remove the valve stem oil seal.
6. Assemble as follows:
SMALL V8 ENGINES
a. Set the valve spring and damper, valve shield
and valve cap in place. Compress the spring
with Tool J-5892 and install oil seal in the lower
groove of the stem, making sure the seal is flat
and not twisted.
NOTE: A light coat of oil on the seal will
help prevent twisting.
Fig. 8V—Valve Adjustment
b. Install the valve locks and release the compres&shy;
sor tool making sure the locks seat properly in
the upper groove of the valve stem.
NOTE: Grease may be used to hold the locks
in place while releasing the compressor tool.
MARK IV V8 ENGINES
a. Install new valve stem oil seal (coated with oil)
in position over valve guide.
NOTE: Seal installation instructions are
supplied with each service kit. Install seal
following procedures outlined on the supplied
instruction sheet.
b. Set the valve spring and damper and valve cap
in place.
c. Compress the spring with Tool J-5892 and install
the valve locks then release the compressor tool,
making sure the locks seat properly in the
groove of the valve stem.
NOTE: Grease may be used to hold the locks
in place while releasing the compressor tool.
7. Install spark plug and torque to specifications.
8. Install and adjust valve mechanism as outlined.
Cylinder Head Assembly
Removal
1.
2.
3.
4.
Remove intake manifold as outlined.
Remove exhaust manifolds as outlined.
Remove valve mechanism as outlined.
Drain cylinder block of coolant.
LIGHT DUTY TRUCK SERVICE MANUAL
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6-53
J -2 3 5 9 0
FRONT
SEAL
Fig. 9V—Compressing Valve Spring
5. Remove cylinder head bolts, cylinder head and
gasket. Place cylinder head on two blocks of wood
to prevent damage.
Installation
CAUTION:
The gasket surfaces on both the
head and the block must be clean of any
foreign matter and free of nicks or heavy
scratches. Cylinder bolt threads in the block
and threads on the cylinder head bolts must be
clean. (Dirt will affect bolt torque).
1. On engines using a STEEL gasket, coat both sides
of a new gasket with a good sealer. Spread the
sealer thin and even. One method of applying the
sealer that will assure the proper coat is with the
use of a paint roller. Too much sealer may hold the
gasket away from the head or block.
CAUTION: Use no sealer on engines using a
composition STEEL ASBESTOS gasket.
2.
3.
4.
5.
6.
7.
Place the gasket in position over the dowel pins
with the bead up.
Carefully guide the cylinder head into place over
the dowel pins and gasket.
Coat threads of cylinder head bolts with sealing
compound and install bolts finger tight.
Tighten each cylinder head bolt a little at a time in
the sequence shown in the torque sequence chart
until the specified torque is reached.
Install exhaust manifolds as outlined.
Install intake manifold as outlined.
Fig. 10V—Oil Pan Gasket and Seal Location
8. Install and adjust valve mechanism as outlined.
Oil Pan
Removal
1. Drain engine oil.
2. Remove oil dip stick and tube.
3. On vehicles so equipped remove exhaust crossover
pipe.
4. On vehicles equipped with automatic transmission
remove converter housing under pan.
5. Remove starter brace and inboard bolt, -swing
starter as^de.
a. Remove engine front mount bolts (frame
bracket-to-mount).
6. Remove oil pan and discard gaskets and seals.
Installation
1. Thoroughly clean all gasket and seal surfaces on oil
pan, cylinder block, crankcase front cover and rear
main bearing cap.
2. Install new oil pan side gaskets on cylinder block
using gasket sealer as a retainer. Install new oil pan
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 5 4 E N G IN E
3.
4.
5.
6.
7.
8.
rear seal in rear main bearing cap groove, with
ends butting side gaskets. Install new oil pan front
seal in groove in crankcase front cover with ends
butting side gaskets (fig. 10V).
Install oil pan and torque bolts to specifications.
Install starter brace and attaching bolts. Torque
bolts to specifications.
Install converter housing under pan (if removed).
Install exhaust crossover pipe (if removed).
Install oil dip stick tube and dip stick.
Fill with oil, start engine and check for leaks.
Oil Pump
Removal
1. Remove oil pan as outlined.
2. Remove pump to rear main bearing cap bolt and
remove pump and extension shaft.
1. With the oil pan and oil pump removed, remove
the rear main bearing cap.
2. Remove oil seal from the bearing cap by prying
from the bottom with a small screw driver (fig.
12V).
3. To remove the upper half of the seal, use a small
hammer to tap a brass pin punch on one end of
seal until it protrudes far enough to be removed
with pliers (fig. 13V).
4. Clean all sealant and foreign material from
cylinder case bearing cap and crankshaft, using a
non-abrasive cleaner.
5. Inspect components for nicks, scratches, burrs and
machining defects at all sealing surfaces, case
assembly and crankshaft.
6. Coat seal lips and seal bead with light engine oil keep oil off seal mating ends.
Installation
1. Assemble pump and extension shaft to rear main
bearing cap, aligning slot on top end of extension
shaft with drive tang on lower end of distributor
drive shaft.
2. Install pump to rear bearing cap bolt and torque to
specifications.
NOTE: Installed position of oil pump screen
is with bottom edge parallel to oil pan rails.
3. Install oil pan as outlined.
Oil Seal (Rear Main)
Replacement
NOTE: Always replace the upper and lower
seal as a unit. Install seal with lip facing front
of engine.
The rear main bearing oil seal can be replaced (both
halves) without removal of the crankshaft. Extreme care
should be exercised when installing this seal to protect
the sealing bead located in the channel on the outside
diameter of the seal. An installation tool (fig. 1IV) can
be used to protect the seal bead when positioning seal as
follows:
Fig. 1IV—Oil Seal Installation Tool
Fig. 12V—Removing Oil Seal (Lower Half)
Fig. 13V—Removing Oil Seal (Upper Half)
LIGHT DUTY TRUCK SERVICE MANUAL
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7. Position tip of tool between crankshaft and seal seat
in cylinder case.
8. Position seal between crankshaft and tip of tool so
that seal bead contacts tip of tool.
NOTE: Make sure that oil-seal lip is
positioned toward front of engine (fig. 14V).
9. Roll seal around crankshaft using tool as a
“shoehorn” to protect seal bead from sharp corner
of seal seat surface in cylinder case.
CAUTION: Installation tool must remain in
position until seal is properly positioned with
both ends flush with block.
10. Remove tool, being careful not to withdraw seal.
11. Install seal half in bearing cap, again using tool as
a “shoehorn”, feeding seal into cap using light
pressure with thumb and finger.
12. Install bearing cap to case with sealant applied to
the cap-to-case interface being careful to keep
sealant off the seal split line (fig. 15V).
13. Install the rear main bearing cap (with new seal)
and torque to specifications.
NOTE: Tool J-23523 has holes forming two
patterns. A two bolt and a three bolt pattern.
The holes for the two bolt pattern must be
elongated for use on the Mark IV V8 engines.
Installation
CAUTION: The inertial weight section o f the
1.
2.
3.
Torsional Damper
Removal
1. Remove fan belt, fan and pulley.
2. Remove the radiator shroud assembly as outlined in
Section 13.
NOTE: If additional operations (such as
camshaft removal) are not being performed,
the radiator removal will not be necessary.
3. Remove accessory drive pulley then remove damper
retaining bolt.
4. Install Tool J-23523 on damper then, turning puller
screw, remove damper (fig. 16V).
6 -5 5
4.
5.
6.
7.
8.
torsional damper is assembled to the hub with a
rubber type material. The installation proce&shy;
dures (with proper tool) must be followed or
movement of the inertia weight section on the
hub will destroy the tuning o f the torsional
damper.
Coat front cover seal contact area (on damper) with
engine oil.
Place damper in position over key on crankshaft.
Pull damper onto crankshaft as follows:
a. Install appropriate threaded end of Tool J-23523
into crankshaft.
CAUTION: Install tool in crankshaft so that at
least 1/2&quot; o f thread engagement is obtained.
b. Install plate, thrust bearing and nut to complete
tool installation.
c. Pull damper into position as shown in Figure
17
V.
d. Remove tool from crankshaft then install
damper retaining bolt and torque to
specifications.
Install accessory drive pulley.
Install radiator shroud as outlined in Section 13.
Install fan and pulley to water pump hub and
tighten securely.
Install fan belt and adjust to specifications using
strand tension gauge.
Fill cooling system, start engine and check for
leaks.
Crankcase Front Cover
Removal
DUST SEAL
Small V8 Engine
OIL SEAL
1.
2.
3.
4.
Remove oil pan as outlined.
Remove torsional damper as outlined.
Remove water pump as outlined in Section 6K.
Remove crankcase front cover attaching screws and
remove front cover and gasket, then discard gasket.
M ark IV V8 Engine
Fig. 14V—Crankshaft Oil Seal (Rear Main)
1. Remove torsional damper and water pump as
outlined.
2. Remove the two, oil pan-to-front cover attaching
screws.
3. Remove the front cover-to-block attaching screws.
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 5 6 E N G IN E
APPLY
SEALANT
TO SHADED
AREAS ONLY
Fig. 15V—Sealing Bearing Cap
Fig. 16V—Removing Torsional Damper
Fig. 17V—Installing Torsional Damper
4. Puil the cover slightly forward only enough to
permit cutting of oil pan front seal.
5. Using a sharp knife or other suitable cutting tool,
cut oil pan front seal flush with cylinder block at
both sides of cover (fig. 18V).
6. Remove front cover and attaching portion of oil
pan front seal. Remove front cover gasket.
Installation
Small V8 Engine
1. Make certain that cover mounting face and cylinder
block front end face are clean and flat.
2. Coat the oil seal with engine oil and using a new
cover gasket, coated with gasket sealer install cover
and gasket over dowel pins and cylinder block.
3. Install cover screws and torque to specifications.
4. Install water pump as outlined in Section 6K.
5. Install torsional damper as outlined.
6. Install oil pan as outlined.
Fig. 18V—Cutting Tabs on Oil Pan Front Seal
Mark IV V8 Engine
1. Clean gasket surface on block and crankcase front
cover.
2. Cut tabs from the new oil pan front seal (fig. 19V),
use a sharp instrument to ensure a clean cut.
3. Install seal to front cover, pressing tips into holes
provided in cover.
4. Coat the gasket with gasket sealer and place in
position on cover.
5. Apply a 1/8 inch bead of silicone rubber sealer,
part 1051435 (or equivalent) to the joint formed at the
oil pan and cylinder block (fig. 20V).
6. Position crankcase front cover over crankshaft.
7. Press cover downward against oil pan until cover is
aligned and installed over dowel pins on block.
LIGHT DUTY TRUCK SERVICE MANUAL
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6-57
Fig. 19V—Oil Pan Front Seal Modification
8. Install and partially tighten the two, oil pan-to-front
cover attaching screws.
9. Install the front cover-to-block attaching screws.
10. Torque all screws to specifications.
11. Install torsional damper and water pump as
outlined.
Oil Seal (Front Cover)
Replacement
With Cover Removed
1. With cover removed, pry oil seal out of cover from
the front with a large screw driver.
2. Install new seal so that open end of the seal is
toward the inside of cover and drive it into position
with Tool J-23042 on Small V8 engines or Tool
J-22102 on Mark IV V8 engines (fig. 21V).
CAUTION: Support cover at seal area. (Tool
J-971 may be used as support).
Fig. 20V—Applying Front Cover Sealer
Fig. 21V—Installing Oil Seal (Cover Removed)
Without Cover Removed
1. With torsional damper removed, pry seal out of
cover from the front with a large screw driver,
being careful not to damage the surface on the
crankshaft.
2. Install new seal so that open end of seal is toward
the inside of cover and drive it into position with
Tool J-23042 on Small V8 engines or Tool J-22102
on Mark IV V8 engines (fig. 22V).
Timing Chain and/or Sprockets
Replacement
1. Remove torsional damper and crankcase front
cover as outlined.
2. Crank engine until marks on camshaft and
crankshaft sprockets are in alignment (fig. 23V).
3. Remove camshaft sprocket to camshaft bolts.
4. Remove camshaft sprocket and timing chain
together. Sprocket is a light press fit on camshaft. If
sprocket does not come off easily, a light blow on
the lower edge of the sprocket (with a plastic
mallet) should dislodge the sprocket.
5. If crankshaft sprocket is to be replaced on Small V8
engines remove sprocket using Tool J-5825 (fig.
24V). Install new sprocket using bolt and nut from
J-23523 (fig. 25V). On Mark IV V8 engines remove
sprocket using Tool J-1619 (fig. 26V). Install new
sprocket using bolt and nut from Tool J-23523 (fig.
25V).
6. Install timing chain on camshaft sprocket. Hold the
sprocket vertically with the chain hanging down
and align marks on camshaft and crankshaft
sprockets (fig. 27V).
NOTE: Do not attempt to drive sprocket on
camshaft as welsh plug at rear of engine can
be dislodged.
LIGHT DUTY TRUCK SERVICE MANUAL
6 5 8 E N G IN E
J-23042
Fig. 22V—Installing Oil Seal (Cover Installed)
7. Draw camshaft sprocket onto camshaft, using the
three mounting bolts. Torque to specifications.
Fig. 23V—Timing Sprocket Alignment Marks
8. Lubricate timing chain with engine oil.
9. Install crankcase front cover and torsional damper
as outlined.
Camshaft
Measuring Lobe Lift
1.
2.
Fig. 2 4 V — R em o v in g C ra n k s h a ft S p ro c k e t (S m a ll V 8 )
3.
4.
5.
Fig. 25V—Installing Crankshaft Sprocket
6.
NOTE: Procedure is similar to that used for
checking valve timing. If improper valve
operation is indicated, measure the lift of
each push rod in consecutive order and
record the readings.
Remove the valve mechanism as outlined.
Position indicator with ball socket adapter (Tool
J-8520) on push rod (fig. 28V).
NOTE: Make sure push rod is in the lifter
socket.
Rotate the crankshaft slowly in the direction of
rotation until the lifter is on the heel of the cam
lobe. At this point, the push rod will be in its lowest
position.
Set dial indicator on zero, then rotate the
crankshaft slowly, or attach an auxiliary starter
switch and “bump” the engine over, until the push
rod is in fully raised position.
CAUTION: Whenever the engine is cranked
remotely at the starter, with a special jumper
cable or other means, the distributor primary
lead must be disconnected from the negative
post on the coil.
Compare the total lift recorded from the dial
indicator with specifications.
Continue to rotate the engine until the indicator
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6-59
w asher
(TORSIONAL DAMPER)
Fig. 2 6 V —Removing Crankshaft Sprocket (Mark ! V V8)
reads zero. This will be a check on the accuracy of
the original indicator reading.
7. If camshaft readings for all lobes are within
specifications, remove dial indicator assembly.
8. Install and adjust valve mechanism as outlined.
Removal
1. Remove valve lifters as outlined.
2. Remove crankcase front cover as outlined.
3. Remove grille (if necessary) as outlined in Section
13.
4. Remove fuel pump push rod as outlined in Section
6M.
5. Complete camshaft removal as follows:
NOTE: Sprocket is a light fit on camshaft. If
sprocket does not come off easily a light blow
on the lower edge of the sprocket (with a
plastic mallet) should dislodge the sprocket.
6. Install two 5/16&quot; x 18 x 4&quot; bolts in camshaft bolt
holes then remove camshaft (fig. 29V).
C A U T IO N :^ // camshaft journals are the same
diameter and care must be used in removing
camshaft to avoid damage to bearings.
Fig. 27V—Installing Timing Chain
Installation
NOTE: Whenever a new camshaft is installed
coat camshaft lobes with “ Molykote” or its
equivalent.
1. Lubricate camshaft journals with engine oil and
install camshaft.
2. Install timing chain on camshaft sprocket. Hold the
sprocket vertically with the chain hanging down,
Fig. 28V—Measuring Camshaft Lobe Lift
and align marks on camshaft and crankshaft
sprockets. (Refer to fig. 23V and 27V).
3. Align dowel in camshaft with dowel hole in
LIGHT DUTY TRUCK SERVICE MANUAL
6 6 0 E N G IN E
Checking Engine Mounts
Front Mount
Raise the engine to remove weight from the mounts and
to place a slight tension in the rubber. Observe both
mounts while raising engine. If an engine mount
exhibits:
a. Hard rubber surface covered with heat check
cracks;
b. Rubber separated from a metal plate of the
mount; or
c. Rubber split through center.
Replace the mount. If there is relative movement
between a metal plate of the mount and its attaching
points, lower the engine on the mounts and tighten the
screws or nuts attaching the mount to the engine, frame,
or bracket.
Fig. 29V—Removing Camshaft
4.
5.
6.
7.
8.
9.
camshaft sprocket then install sprocket on
camshaft.
Draw the camshaft sprocket onto camshaft using
the mounting bolts. Torque to specifications.
Lubricate timing chain with engine oil.
Install fuel pump push rod as outlined in Section
6M.
Install grille as outlined in Section 13.
Install crankcase front cover as outlined.
Install valve lifters as outlined.
Flywheel
Removal
With transmission and/or clutch housing and clutch
removed from engine, remove the flywheel.
Rear Mount
Raise the vehicle on a hoist. Push up and pull down on
the transmission tailshaft while observing the transmis&shy;
sion mount. If the rubber separates from the metal plate
of the mount or if the tailshaft moves up but not down
(mount bottomed out) replace the mount. If there is
relative movement between a metal plate of the mount
and its attaching point, tighten the screws or nuts
attaching the mount to the transmission or crossmember.
Front Mount Replacement
1. Remove distributor cap.
2. Remove mount retaining bolt from below frame
mounting bracket.
3. Raise front of engine and remove mount-to-engine
bolts and remove mount.
CAUTION: Raise engine only enough for
Installation
1. Clean the mating surfaces of flywheel and
crankshaft to make certain there are no burrs.
2. Install flywheel on crankshaft and position to align
dowel hole of crankshaft flange and flywheel (fig.
30V).
NOTE: On Automatic Transmission
equipped engines, the flywheel must be
installed with the flange collar to transmis&shy;
sion side (fig. 30V).
3. Coat thread end of bolts with sealer then install
bolts and torque to specifications.
CONVERTER |&quot;^ R IN G
BOLT AREA ^
GEAR
DEPRESSED
I
WELDS
ÊNGINE
Engine Mounts
Engine mounts (fig. 31V - 36V) are the non-adjustable
type and seldom require service. Broken or deteriorated
mounts should be replaced immediately, because of the
added strain placed on other mounts and drive line
components.
SYNCHROMESH
TRANS.
AUTOMATIC
Fig. 30V—Flywheel Installation (Typical)
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
sufficient clearance. Check for interference
between rear of engine and cowl panel.
4. Replace mount to engine and lower engine into
place.
5. Install retaining bolt and torque all bolts to
specifications.
Rear Mount Replacement
1. Support engine weight to relieve rear mounts.
2. Remove crossmember-to-mount bolts.
3. On P Series with manual transmission and
propeller shaft parking brake, remove mount
4.
5.
6.
7.
8.
6-61
attaching bolts from frame outrigger and clutch
housing and remove rear mounting cushions.
Remove mount-to-tfansmission bolts, then remove
mount.
On P Series with manual transmission and
propeller shaft parking brake, install new mounting
cushions and bolts.
Install new mount on transmission.
While lowering transmission, align and start
crossmember-to-mount bolts.
Torque bolts to specifications then bend lock tabs to
bolt head as applicable.
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 6 2 E N G IN E
M A N U A L TR A N SM ISSIO N
W ITH PROPELLER SHAFT PAR KING BRAKE
ALL TURBO H Y D R A -M A T IC 4 0 0
(EXCEPT MOBILE H O M E CHASSIS)
W ITH O U T PROPELLER SHAFT PARKING BRAKE
ALL M A N U A L TRAN SM ISSIO N
ALL TURBO H Y D R A -M A T IC 3 5 0
A U T O M A T IC TR A N SM ISSIO N
ALL MOBILE H O M E CHASSIS
W ITHO UT PROPELLER SHAFT PARKING BRAKE
W ITH PROPELLER SHAFT PA R K IN G BRAKE
Fig. 31V—P Series Engine Rear Mount
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
6-63
VIEW A
A
3 5 0 CU. IN .
/
M O TO R H O M E CHASSIS
454 cu
|N
VIEW
FWD
4 5 4 CU
VIEW
ALL EXCEPT M O TO R H O M E CHASSIS
FWD
307 &amp;
Fig. 32V—P Series Engine Front Mount
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 6 4 E N G IN E
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
6-65
LIGHT DUTY TRUCK SERVICE MANUAL
6 - 6 6 E N G IN E
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E
6 -6 7
Fig. 36V—C Series Engine Mounts
LIGHT DUTY TRUCK SERVICE MANUAL
6-68
ENGINE
DIAGNOSIS
ENGINE FAILS TO START
CAUSE
a. Corroded or loose battery terminal connections
and/or weak battery.
Broken or loose ignition wires and/or faulty
ignition switch.
c. Excessive moisture on plugs, caps or ignition
system.
d. Damaged distributor rotor, cracked distributor cap
and/or corroded distributor contact points.
e. Fouled spark plugs and/or improper spark plug
gaP-
f. Weak or faulty coil.
Carburetor flooded and/or fuel level in carburetor
bowl not correct.
h. Dirt and water in gas line or carburetor.
i. Sticking choke.
j- Faulty fuel pump.
k. Faulty solenoid or starting motor.
Park or neutral switch inoperative.
ENGINE LOPES WHILE IDLING
a.
b.
c.
d.
CAUSE
Air leaks between intake manifold and head.
Blown head gasket.
Worn timing chain or sprockets.
Worn camshaft lobes.
e.
f.
g.
h.
Overheated engine.
Plugged crankcase vent valve.
Faulty fuel pump.
Leaky exhaust gas recirculation valve.
ENGINE MISSES WHILE IDLING
CAUSE
a.
b.
c.
d.
e.
f.
g.
h.
i.
Spark plugs damp or gap incorrectly set.
Excessive moisture on ignition wires and caps.
Leaks in ignition wiring.
Ignition wires making poor contact.
Uneven compression.
Burned, pitted or incorrectly set contact points.
Faulty coil or condenser.
Worn distributor cam or cracked distributor cap.
Incorrect carburetor idle adjustment and/or dirty
jets or plugged passages in carburetor.
j. Foreign matter, such as dirt or water, in gas line or
carburetor.
k. Air leak at carburetor mounting gasket.
1. Choke inoperative.
m. Faulty spark advance mechanism.
Burned, warped, pitted, or sticking valves.
Incorrect valve lifter clearance.
Low compression.
Leak in exhaust gas recirculation valve.
ENGINE MISSES AT VARIOUS SPEEDS
a.
b.
c.
d.
e.
f.
CAUSE
Dirt and water in gas line or carburetor.
Fouled carburetor jets.
Incorrect ignition timing.
Points dirty, pitted or incorrectly spaced.
Excessive play in distributor shaft.
Insufficient spring tension on points.
g- Distributor cam lobe worn.
h. Weak coil or condenser.
i. Spark plugs dirty or damp and/or gaps set too wide.
j-
k.
1.
m.
n.
o.
Pq-
Insufficient point dwell.
Detonation or pre-ignition.
Excessively worn fuel pump diaphragm.
Weak valve spring.
Worn camshaft lobes.
Engine overheating.
Sub-standard fuel.
Leak in exhaust gas recirculation valve.
ENGINE
6-69
ENGINE STALLS
CAUSE
a. Carburetor idle speed set too low and/or idle
mixture too rich or too lean.
b. Carburetor needle valve and seat inoperative.
c. Incorrect carburetor float level and/or carburetor
flooding.
d. Dirt or water in gasoline or carburetor.
e. Choke improperly adjusted or sticking.
f. Faulty ignition system.
g- Spark plugs damp or dirty and/or gaps incorrectly
set.
h. Faulty coil or condenser.
i. Distributor points burned, pitted, dirty, or incor&shy;
rectly set.
j- Distributor advance inoperative.
k. Exhaust system restricted.
1 Leaks in carburetor mounting gasket or intake
manifold.
m. Incorrect valve lifter clearance.
n. Burned, warped, or sticking valves.
Low compression.
0
P- Engine overheating.
q- Loose, corroded, or leaking wiring connections
(bulkhead connector, etc.)
Leak
in exhaust gas recirculation valve.
r.
.
.
ENGINE HAS NO POWER
CAUSE
a. Weak coil or condenser.
b. Incorrect ignition timing.
c. Excessive play in distributor shaft or distributor
cam worn.
d. Insufficient point dwell.
e. Spark plugs dirty or gaps incorrectly set.
f. Carburetor not functioning properly.
g- Improper carburetor float level.
h. Carburetor fuel mixture too rich or too lean.
i. Foreign matter, such as dirt or water, in gas line or
carburetor.
J- Faulty fuel pump.
k. Valve spring weak and/or valves sticking when hot.
l. Valve timing incorrect.
m. Incorrect valve lifter clearance.
n. Worn camshaft lobes.
Pistons incorrectly fitted in block.
0
P- Blown cylinder head gasket.
q- Low compression.
r. Flow control valve inoperative (Power Steering).
s. Clutch slipping.
t. Brakes dragging.
u. Engine overheating.
Transmission regulator valve sticking (HydraMatic).
w. Sub-standard fuel.
.
V.
EXTERNAL ENGINE OIL LEAKAGE
CAUSE
a.
b.
c.
d.
e.
f.
Improperly seated or broken fuel pump gasket.
Improperly seated or broken push rod cover gasket.
Improperly seated or broken oil filter gasket.
Broken or improperly seated oil pan gasket.
Gasket surface of oil pan bent or distorted.
Improperly seated or broken timing chain cover
gasket.
g- Worn timing chain cover oil seal.
h. Worn or improperly seated rear main bearing oil
seal.
Loose oil line plugs.
j- Engine oil pan drain plug improperly seated.
k. Rear camshaft bearing drain hole plugged.
Loose rocker arm cover, gasket broken, or cover
distorted or bent.
LIGHT DUTY TRUCK SERVICE MANUAL
6-70
ENGINE
EXCESSIVE OIL CONSUMPTION DUE TO OIL ENTERING
COMBUSTION CHAMBER THROUGH HEAD AREA
CAUSE
a. Intake valve seals damaged or missing.
b. Worn valve stems or guides.
c. Plugged drain back holes in head.
d. Intake manifold gasket leak in conjunction with
rocker cover gasket leak.
EXCESSIVE OIL CONSUMPTION DUE TO OIL ENTERING
COMBUSTION CHAMBER BY PASSING PISTON RINGS
CAUSE
a. Oil level too high.
b. Excessive main or connecting rod bearing
clearance
c. Piston ring&deg; gaps not staggered.
OD
d. Incorrect size rings installed.
e. Piston rings
&deg; out of round, broken or scored.
f. Insufficient piston ring tension due to engine
overheating.
g.
h.
i.
J&gt;k.
1.,
Ring grooves or oil return slots clogged.
Rings sticking in ring grooves of piston,
Ring grooves worn excessively in piston.
^Compression
• rings
• installed
• ,, , upside
. . .down.
• , worn or scored .cylinder
..
Excessively
walls.
~Oil, too thin.
..
NO OIL PRESSURE WHILE IDLING
CAUSE
a. Faulty oil gauge sending unit.
b. Oil pump not functioning properly. (Regulator ball
stuck in position by foreign material).
c. Excessive clearance at main and connecting rod
bearings.
d. Loose camshaft bearings.
e. Leakage at internal oil passages.
NO OIL PRESSURE WHILE ACCELERATING
a. Low oil level in oil pan.
CAUSE
b- Leakage at internal oil passages.
BURNED, STICKING OR BROKEN VALVES
CAUSE
a. Weak valve springs.
b. Improper valve lifter clearance.
c. Improper valve guide clearance and/or worn valve
guides.
d. Out-of-round valve seats or incorrect valve seat
width.
e. Deposits on valve seats and/or gum formation on
stems or guides.
f
Wart'ed valves or faul|y valve forSinSsg. Exhaust back pressure.
h. Improper spark timing,
LIGHT DUTY TRUCK SERVICE MANUAL
ENGINE
6-71
NOISY VALVES
CAUSE
a.
b.
c.
d.
Incorrect valve lifter clearance.
Excessively worn, dirty or faulty valve lifters.
Worn valve guides.
Excessive run-out of valve seat or valve face.
e.
f.
g.
h.
Worn camshaft lobes.
Pulled or loose rocker arm studs.
Bent push rods.
Broken valve spring.
NOISY PISTONS AND RINGS
CAUSE
a. Excessive clearance between piston and bore.
b. Improper fit of piston pin.
c. Excessive accumulation of carbon in heads.
d. Connecting rods improperly aligned.
e. Excessive clearance between rings and grooves.
f. Rings broken.
BROKEN PISTONS AND/OR RINGS
CAUSE
a.
b.
c.
d.
Undersize pistons installed.
Wrong type and/or size rings installed.
Cylinder bores tapered or eccentric.
Connecting rods improperly aligned.
e.
f.
g.
h.
i.
Excessively worn ring grooves.
Pins improperly assembled.
Insufficient ring gap clearance.
Engine overheating.
Fuel of too low octane rating.
NOISY CONNECTING RODS
a. Connecting rods improperly aligned.
b. Excessive bearing clearance.
c. Eccentric or out-of-round crankshaft journals.
CAUSE
d. Insufficient oil supply.
e. Low oil pressure.
f. Connecting rod bolts not tightened correctly.
NOISY MAIN BEARINGS
a.
b.
c.
d.
Low oil pressure and/or insufficient oil supply.
Excessive bearing clearance.
Excessive crankshaft end play.
Eccentric or out-of-round crankshaft journals.
CAUSE
e. Sprung crankshaft.
f. Excessive belt tension.
g. Loose torsional damper.
NOISY VALVE LIFTERS
a.
b.
c.
d.
e.
f.
Broken valve springs.
Worn or sticking rocker arms.
Worn or bent push rods.
Valve lifters incorrectly fitted to bore size.
Faulty valve lifter plunger or push rod seat.
Plungers excessively worn causing fast leakdown
under pressure.
g. Excessively worn camshaft lobes.
h. Valve lifter oil feed holes plugged causing internal
breakdown.
i. Faulty valve lifter check ball. (Nicked, flat spot, or
out of round).
&gt;■ Rocker a™ retaining nut installed upside down.
k. End of push rod excessively worn or flaked.
LIGHT DUTY TRUCK SERVICE MANUAL
6-72
ENGINE
TORQUE SPECIFICATIONS
CYLIND ER HEAD TORQUE SEQUENCE
L6
S M A L L V8'
' M A R K IV V 8 '
IN TA K E MANIFOLD TORQUE SEQ UEN CE
FRONT
“ SMALL V 8 “
&quot; MA RK I V V 8 ”
Fig. IT —Torque Sequence
LIGHT DUTY TRUCK SERVICE MANUAL
ENGINE
6-73
SPECIAL TOOLS
1.
2.
11.
12.
13.
J-4536
J-1264
J-8058
J-5853
J-8087
J-8001
J-23600
J-8037
J-8020
J-8021
J-8032
J-22249
J-22147
J-22250
J-6994
J-9510
J-5239
J-6305
J-8062
J-8101
J-5830
14.
15.
J-7049
J-8089
J-5860
3.
4.
5.
6.
7.
8.
9.
10.
Engine L if t K it
(0-200 F t. Lb.) Torque Wrench
(0-50 Ft. Lb.)
(0-100 in lb.)
In d ica to r Set (C ylin d e r Bore)
In d ica to r Set (Universal)
Belt Tension Gauge
Piston Ring Compressor
(3 -9 /1 6 ” ) Piston Ring Expander
(3 -7 /8 ” )
(4 ” )
(3 -1 5 /1 6 ” )
(4 -3 /3 2 ” )
(4 -1 /4 ” )
Piston Pin Assembly Tool
Piston Pin Assembly Tool
(3 /8 ” ) Connecting Rod Guide Set
(1 1 /3 2 ” )
Valve Spring Compressor
Valve Guide Cleaner
(1 1 /3 2 ” ) Valve Guide Reamer
Set
(3 /8 ” )
Carbon Removing Brush
C ylinder Head B o lt Wrench
16.
J-5715
17.
18.
19.
J-6036
J-6880
J-5802
J-9534
20
J-9535
21
22
23
24.
25
26
27.
28
29.
30
J-22 144
J-8369
J-6098
J-097 1
J-23523
J-22 197
J-1619
J-5825
J-8 105
J-5590
31
J-23042
32
J-22102
(.0 0 3 ” ) Rocker A rm Stud
Reamer
(.0 1 3 ” )
Rocker A rm Stud Installer
Rocker A rm Stud Remover
D is trib u to r Low er Bushing
Remover
D istributor Lower Bushing
Installer
Oil Pick-up Screen Installer
Oil Pick-up Screen Installer
Cam Bearing Tool
Camshaft Gear Support
Torsional Damper Puller
Torsional Damper Installer
Crankshaft Sprocket Puller
Crankshaft Sprocket Puller
Crankshaft Gear Puller
Crankshaft Sprocket or Gear
Installer
Crankcase Cover Centering
Gauge and Seal Installer
Crankcase Cover Seal Installer
TOOLS NOT ILLUSTRATED
Valve Seal Leak Detector
J-23994
Fig. 2T—Special Tools
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E C O O L IN G
6K-1
SECTION 6K
ENGINE COOLING
INDEX
General Description........................................................
Theory of Operation.......................................................
Maintenance and Adjustments....................................
Coolant Level...................................................................
Coolant System Checks................................................
Periodic Maintenance...................................................
Cleaning..........................................................................
Reverse Flushing..........................................................
Radiator........................................................................
Cylinder Block and Cylinder H ead....................
6K-1
6K-2
6K-7
6K-7
6K-7
6K-8
6K-8
6K-8
6K-8
6K-8
Heater Core..................................................................
Fan Belt Adjustment.....................................................
Radiator C ap ...................................................................
Thermostat........................................................................
Replacement...................................................................
Thermostatic Fan Clutch Replacement..................
Water Pum p.....................................................................
Removal..........................................................................
Installation......................................................................
Diagnosis..............................................................................
6K-9
6K-9
6K-9
6K-9
6K-9
6K-9
6K-10
6K-10
6K-11
6K-11
GENERAL DESCRIPTION
Fig. 1—Radiator Pressure Cap
All trucks have pressure type engine cooling sys&shy;
tems with thermostatic control of coolant circulation.
The cooling system is sealed by a pressure type radiator
filler cap.
The pressure type radiator filler cap (fig. 1) is designed to
operate the cooling system at higher than atmospheric
pressure. The higher pressure raises the boiling point of
the coolant which increases the efficiency of the radiator.
The radiator filler cap contains a pressure relief valve
and a vacuum relief valve. The pressure relief valve is
held against its seat by a spring which when compressed,
allows excessive pressure to be relieved out the radiator
overflow.
The vacuum valve is also held against its seat by a spring
which when compressed, opens the valve relieving the
vacuum created when the system cools.
The cooling system’s water pump is of the centrifugal
vane impeller type (figs. 2 and 3). The bearings are
permanently lubricated during manufacture and are
sealed to prevent the loss of lubricant or the entry of dirt
and water. The pump requires no care other than to
make certain the air vent at the top of the housing and
Fig. 2—Water Pump—Typical L-6
the drain holes in the bottom do not become plugged
with dirt or grease.
Water pump components are not serviced separately;
therefore, in the event of water pump failure, it will be
necessary to replace the complete assembly — removal
and installation procedures are covered in this section.
For radiator service refer to Section 13 of this manual.
Radiator fan shroud replacement is covered in Section
11 of this manual.
LIGHT DUTY TRUCK SERVICE MANUAL
6 K - 2 E N G IN E C O O L IN G
Fig. 3—Water Pump—Typical V-8
THEORY OF OPERATION
The engine cooling system is designed to maintain the
tfngine at its most efficient operating temperature at all
engine speeds and all driving conditions. During
combustion of the air-fuel mixture, combustion gas
temperatures may be as high as 4500 degrees. The
cylinder walls, cylinder heads and pistons absorb some
but not all of the heat. They, in turn, must be provided
with some means of cooling to prevent permanent
damage. Temperatures higher than the limit imposed by
the oil properties will destroy the lubricating characteris&shy;
tics of the oil and lead to subsequent engine failure. It is
desirable to operate the engine at a temperature as close
as possible to the limit imposed by the oil properties.
Removing too much heat would lower the thermal
efficiency; therefore, the cooling system functions to
remove approximately 35 percent of the heat produced
during combustion.
COOLING SYSTEM CIRCULATION
Six-Cylinder Engine
The water pump discharges coolant into the water jacket
chamber between the front face of the block and the
number one cylinder (Fig. 4). Coolant then flows through
the block, toward the rear, passing through two large cast
openings into the cylinder head, to cool the valve seats,
and forward to the water outlet at the front of the head.
Some coolant is directed through a small hole in the
cylinder head gasket to an area around each spark plug.
During engine warm-up, when the thermostat is closed,
coolant is redirected to the water pump through a
coolant by-pass in the cylinder head and block. Coolant
circulation, after normal operating temperatures are
reached (thermostat open), flows through the coolant
outlet and the pellet-type thermostat to the radiator.
Eight-Cylinder Engine
The water pump discharges coolant to each bank of
cylinders. The coolant flow is from the front of each
bank around each cylinder and toward the rear of the
block. Large passages connecting the block to cylinder
head directs coolant over and around the alternately
spaced inlet and exhaust ports, as well as around the
exposed exhaust valve guide inserts. Smaller circular
holes permit metered amounts of coolant to pass from
the cylinder block to cored passages surrounding the
spark plugs.
On “Small V8” engines during warm up (thermostat
closed), coolant is redirected, through a small passage
located in the front of the right cylinder head and block
to a mating hole in the extreme lower portion of the
water pump runner.
On “Mark IV” engines during warm up (thermostat
closed), coolant is redirected to the water pump by way
of a recirculating passage in the intake manifold which
is connected externally to the pump body.
Coolant circulation after normal operating temperatures
are obtained (thermostat open), is directed from the
intake manifold through the coolant outlet and
thermostat to the radiator.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E C O O L IN G
6 K -3
Fig. 4—Engine Coolant Circulation (Six-Cylinder)
COMPONENTS
Water Pump
The cooling system water pump is of the centrifugal
vane impeller type. The impeller turns on a steel shaft
that rotates on a double row of permanently lubricated
ball bearings, which are sealed during manufacture to
prevent loss of lubricant and to prevent entry of dirt and
water.
The pump inlet is connected to the bottom of the
radiator by means of a rubber hose. Pump outlet is
separate from the pump and is located in the thermostat
housing which is connected to the top of the radiator by
a rubber hose.
Radiator
Radiators are designed to hold a large volume of coolant
so that the coolant is also exposed to a large volume of
air. The object being to transfer heat produced during
combustion to the coolant and then to transfer heat in
the coolant to air flowing passed the radiator.
Radiators are of the cross-flow type (Fig. 5). The
water flows horizontally from the input (left) tank
through the individual cores to the output (right) tank.
Radiators used on vehicles equipped with automatic
transmission may, in some instances, have oil coolers
into the right (output) tank. Inlet and outlet fittings for
transmission fluid circulation are positioned vertically on
the tank.
Radiator Cap
The pressure type radiator filler cap is designed to
operate the cooling system at higher than atmospheric
pressure. The higher pressure raises the boiling point of
the coolant, which increases the efficiency of the radiator.
The radiator filler cap contains a pressure relief valve
and a vacuum relief valve. The pressure relief valve is
LIGHT DUTY TRUCK SERVICE MANUAL
6 K - 4 E N G IN E C O O L IN G
WARM WATER
FROM ENGINE
COLD RADIATOR TRANSMISSION
FILL LEVEL
OIL COOLER
LINES
RADIATOR CODE' COOLED WATER
TO ENGINE
LOCATION
Fig. 5—Typical Cross-Flow Radiator
held against its seat by a spring, which, when
compressed, allows excessive pressure to be relieved out
the radiator overflow. The vacuum valve is also held
against its seat by a spring which, when compressed,
opens the valve to relieve the vacuum created when the
system cools.
Fan
The cooling fan is located on the end of the water pump
shaft and is driven by the same belt that drives the
pump. In some instances a fan shroud surrounds the fan.
This shroud increases the cooling system efficiency by
ensuring that all air pulled in by the fan passes through
the radiator. Basically there are two types of fans: a fixed
drive fan (which rotates at water pump - engine rpm speed) and the automatic fan clutch.
Automatic fan clutches, Figure 6, are hydraulic devices
used to vary the speed in relation to the engine
temperature. Automatic fan clutches are used with many
engines, especially those equipped with factory installed
air conditioning units. Automatic fan clutches permit the
use of a high delivery fan to insure adequate cooling at
reduced engine speeds while eliminating overcooling,
excessive noise, and power loss at high speeds.
The automatic fan clutch has two modes of operation,
the engaged mode and the disengaged mode. The
disengaged mode (engine cold or high speed driving)
occurs when the silicone fluid is contained in the
reservoir area of the fan clutch. As the temperature of
the engine rises so does the temperature of the bimetallic
coil. This bimetallic coil is connected to the arm shaft in
such a way that as the temperature rises the shaft moves
the arm exposing an opening in the pump plate. This
opening allows the silicone fluid to flow from the
reservoir into the working chamber of the automatic fan
clutch.
The silicone fluid is kept circulating through the fan
clutch by wipers located on the pump plate. A hole is
located in front of each wiper, Figure 7. The speed
differential between the clutch plate and the pump plate
develops high pressure areas in front of the wipers, thus
the fluid is forced back into the reservoir. But as the
temperature rises the arm uncovers more of the large
opening and allows more of the silicone fluid to re-enter
the working chamber.
The automatic fan clutch becomes fully engaged when
the silicone fluid, circulating between the working
chamber and the reservoir, reaches a sufficient level in
the working chamber to completely fill the grooves in the
clutch body and clutch plate.
The resistance of the silicone fluid to the shearing action
caused by the speed differential between the grooves
transmits torque to the clutch body. The reverse situation
occurs when the temperature drops. The arm slowly
closes off the return hole thus blocking the fluid flow
from the reservoir into the working chamber.
The continuous action of the wipers removes the silicone
fluid from the grooves in the working chamber and
reduces the shearing action. Thus, less torque is
transmitted to the clutch body and the speed of the fan
decreases.
The temperature at which the automatic fan clutch
engages and disengages is controlled by the setting of
the bimetallic coil. This setting is tailored to satisfy the
cooling requirements of each model.
FAN CLUTCH DIAGNOSTIC
PROCEDURE
1.
NOISE
Fan noise is sometimes evident under the following
normal conditions: a. when clutch is engaged for
maximum cooling, and b. during first few minutes after
start-up until the clutch can re-distribute the silicone
fluid back to its normal disengaged operating condition
after overnight settling.
However, fan noise or an excessive roar will generally
occur continuously under all high engine speed
conditions (2500 r.p.m. and up) if the clutch assembly is
locked up due to an internal failure. If the fan cannot be
roated by hand or there is a rough grating feel as the
fan is turned, the clutch should be replaced.
2.
LOOSENESS
Under various temperature conditions, there is a visible
lateral movement that can be observed at the tip of the
fan blade. This is a normal condition due to the type of
bearing used. Approximately 1/4&quot; maximum lateral
movement measured at the fan tip is allowable. This is
not cause for replacement.
3.
SILICONE FLUID LEAK
The operation of the unit is generally not affected by
small fluid leaks which may occur in the area around the
bearing assembly. However, if the degree of leakage
appears excessive, proceed to item 4.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E C O O L IN G
- F------ /
WORKING CHAMBER v
A
.BALL BEARING
i| S
_
6 K -5
_
CLUTCH PLATE
W
II
B 1 'W
^
ARM
FLUID RESERVOIR CHAMBER
PUMP PLATE
BIMETALLIC COIL
Fig. 6—Automatic Fan Clutch
4.
CIRCULATING HOLES
ENGINE OVERHEATING
A. Start with a cool engine to ensure complete fan
clutch disengagement. Refer to Item b, paragraph
1.
WIPER
Fig.
7—Fan
Clutch Pump Plate
B. If the fan and clutch assembly free-wheels with no
drag (revolves over 5 times when spun by hand),
the clutch should be replaced. If clutch performs
properly with a slight drag go to step C.
NOTE: Testing a fan clutch by holding the
small hub with one hand and rotating the
aluminum housing in a clockwise/counter&shy;
clockwise motion will cause the clutch to free&shy;
wheel, which is a normal condition when
operated in this manner. This should not be
considered a test by which replacement is
determined.
C. Use dial type thermometer, J6742-01, or similar
type.
NOTE: J6742-01 reads to 180 degrees F,
therefore, allow approximately 3/16&quot; pointer
movement for each 10 degrees over 180
degrees
CAUTION:
Check for adequate clearance
LIGHT DUTY TRUCK SERVICE MANUAL
r
6 K - 6 E N G IN E C O O L IN G
D.
E.
F.
G.
between fan blades and thermometer sensor
before starting engine.
Position thermometer so that the thermometer
sensor is centered in the space between the fan
blades and radiator. This can be achieved by
inserting the sensor through one of the existing
holes in the fan shroud or fan guard, or by placing
between the radiator and the shroud. On some
models, it may be necessary to drill a 3/16&quot; hole in
the fan shroud to insert J6742-01.
Cover radiator grille sufficiently to induce a high
engine temperature. Start engine and turn on air
conditioning if equipped. Maintain a position in
front of the vehicle to observe the thermometer
reading. With a rod, broom handle, or etc., push
on the accelerator linkage to maintain approx&shy;
imately 3000 r.p.m. Use tachometer if available.
Observe thermometer reading when clutch engages.
It will take approximately 5 to 10 minutes for the
temperature to become high enough to allow
engagement of the fan clutch. This will be
indicated by an increase or roar in fan air noise
and by a drop in the thermometer reading of
approximately 5-15 degrees F. If the clutch did not
engage between 165-190 degrees F., the unit should
be replaced.
NOTE: Be sure fan clutch was disengaged at
beginning of test.
CAUTION: Do not continue test past a
thermometer reading o f 190 degrees F to
prevent engine overheating.
If no sharp increase in fan noise or temperature
drop was observed and the fan noise level was
constantly high from start of test to 190 degrees F,
the unit should be replaced.
As soon as the clutch engages, remove the radiator
grille cover and turn off the air conditioning to
assist in engine cooling. The engine should be run
at approximately 1500 r.p.m.
After several minutes the fan clutch should
disengage, as indicated by a reduction in fan speed
and roar.
Fig. 8—Sectional View of Thermostat
As the engine becomes warm, the pellet expands and the
thermostat valve opens, permitting the coolant to flow
through the radiator where heat is passed through the
radiator walls. This opening and closing of the
thermostat valve permits enough coolant to enter the
radiator to keep the engine within operating temperature
limits.
Coolant
Regardless of whether freezing temperatures are or are
not expected, cooling system protection should be
maintained at least to -20&deg;F. to provide adequate
corrosion protection and proper temperature indicating
light operation. With glycol content less than require-
Thermostat
A pellet-type thermostat is used in the coolant outlet
passage to control the flow of engine coolant, to provide
fast engine warm-up and to regulate coolant tempera&shy;
tures. A wax pellet or powder element in the thermostat
expands when heated and contracts when cooled (Fig. 8).
The pellet is connected through a piston to a valve.
When the pellet is heated, pressure is exerted against a
rubber diaphragm which forces the valve to open. As the
pellet is cooled, the contraction allows a spring to close
the valve. Thus, the valve remains closed while the
coolant is cold, preventing circulation of coolant through
the radiator, but allowing the coolant to circulate
throughout the engine to warm it quickly and evenly.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E C O O L IN G
ment for -20&deg;F. protection, coolant boiling point is less
than the temperature indicating light setting. When
adding solution due to loss of coolant for any reason or
in areas where temperatures lower than -20&deg;F. may
occur, a sufficient amount of an ethylene glycol base
coolant that meets GM Specification 1899-M should be
used.
Every two years the cooling system should be serviced by
flushing with plain water, than completely refilled with a
fresh solution of water and a high-quality, inhibited
(permanent-type) glycol base coolant meeting GM
Specification 1899-M and providing freezing protection
at least to -20&deg;F. At this time, also add GM Cooling
6 K -7
System Inhibitor and Sealer or equivalent. In addition,
Cooling System Inhibitor and Sealer should be added
every fall thereafter. GM Cooling System Inhibitor
retards the formation of rust or scale and is compatible
with aluminum components.
NOTE: Alcohol or methanol base coolants or
plain water are not recommended for engine
coolant at any time.
Coolant Recovery System
The coolant recovery system supplements the standard
cooling system in that additional coolant is available
from a translucent plastic reservoir (Fig. 9).
M A IN TEN A N C E A N D ADJUSTMENTS
Coolant Level
NOTE: On vehicles equipped with the
coolant recovery system, the coolant level is
checked by observing the liquid level in the
reservoir. The radiator cap need not be
removed. The coolant level should be at the
“Cold Full” mark when cooling system cools
and coolant is at ambient temperature. After
the vehicle has been driven sufficiently to
obtain normal operating temperature, the
level should be at the “Hot Full” mark.
The radiator coolant level should only be checked when
the engine is cool, particularly on trucks equipped with
air conditioning. If the radiator cap is removed from a
hot cooling system, serious personal injury may result.
The cooling system fluid level in downflow radiators
should be maintained one inch below the bottom of the
filler neck of the radiator when cooling system is cold.
Coolant level in crossflow radiators should be main&shy;
tained three inches below the bottom of the filler neck
when the system is cold to allow for expansion of coolant
when heated. (Note coolant level arrow on rear of
radiator outlet tank.) It is very important that the correct
fluid level be maintained, as too high a level will
overflow from expansion and too low a level will reduce
cooling performance.
All truck cooling systems are pressurized with a 15 lb.
pressure cap which permits safe engine operation at
cooling temperatures of up to 256&deg;F. with a 33% glycol
solution.
When the radiator cap is removed or loosened, the
system pressure drops to atmospheric, and the heat
which had caused water temperature to be higher than
212&deg;F, will be dissipated by conversion of water to steam.
Inasmuch as the steam may form in the engine water
passages, it will blow coolant out of the radiator upper
hose and top tank, necessitating coolant replacement.
Engine operating temperatures higher than the normal
boiling point of water are in no way objectionable so
long as the coolant level is satisfactory when the engine
is cool.
Upon repeated coolant loss, the pressure radiator cap
and seat should be checked for sealing ability. Also, the
cooling system should be checked for loose hose
connections, defective hoses, gasket leaks, etc.
Coolant System Checks
1. Test for restriction in the radiator, by warming the
engine up and then turning the engine off and
feeling the radiator. The radiator should be hot at
the top (along the left side on crossflow radiators)
and warm at the bottom (along the right side on
crossflow radiators), with an even temperature rise
from bottom to top (right to left on crossflow
radiators). Cold spots in the radiator indicate
clogged sections.
2. Water pump operation may be checked by running
the engine while squeezing the upper radiator hose.
A pressure surge should be felt. Check for a
plugged vent-hole in pump.
NOTE: A defective head gasket may allow
exhaust gases to leak into the cooling system.
This is particularly damaging to the cooling
system as the gases combine with the water to
form acids which are harmful to both the
radiator and engine.
WARNING: If you siphon coolant from the
radiator, do not use mouth to start siphoning
action. The coolant solution is POISONOUS
and can cause death or serious illness if
swallowed.
3. To check for exhaust leaks into the cooling system,
siphon coolant from the system until the coolant
level stands just above the top of the cylinder head,
then disconnect the upper radiator hose and remove
the thermostat and fan belt. Start the engine and
quickly accelerate several times. At the same time
note any appreciable water rise or the appearance
of bubbles which are indicative of exhaust gases
leaking into the cooling system.
LIGHT DUTY TRUCK SERVICE MANUAL
6 K - 8 E N G IN E C O O L IN G
Periodic Maintenance
It is the owner’s responsibility to keep the freeze
protection at a level commensurate with the area in
which the vehicle will be operated. Regardless of climate,
system protection should be maintained at least to -20&deg;F.,
to provide adequate corrosion protection. When adding
solution due to loss of coolant for any reason or in areas
where temperatures lower than -20&deg;F. may occur, a
sufficient amount of an ethylene glycol base coolant that
meets GM Specification 1899-M should be used.
Every two years the cooling system should be serviced by
flushing with plain water, then completely refilled with a
fresh solution of water and high-quality inhibited
(permanent-type) glycol base coolant meeting GM
Specification 1899-M, and providing freezing protection
at least to -20&deg;F. At this time, also add GM Cooling
System Inhibitor and Sealer or equivalent. In Addition,
Cooling System Inhibitor and Sealer should be added
every fall thereafter. GM Cooling System Inhibitor
retards the formation of rust or scale and is compatible
with aluminum components.
NOTE: Alcohol or methanol base coolants or
plain water are not recommended for your
cooling system at any time.
Two common causes of corrosion are: (1) air suction—Air
may be drawn into the system due to low liquid level in
the radiator, leaky water pump or loose hose connec&shy;
tions; (2) exhaust gas leakage— Exhaust gas may be
blown into the cooling system past the cylinder head
gasket or through cracks in the cylinder head and block.
Cleaning
A good cleaning solution should be used to loosen the
rust and scale before reverse flushing the cooling system.
There are a number of cleaning solutions available and
the manufacturer’s instructions with the particular
cleaner being used should always be followed.
An excellent preparation to use for this purpose is GM
Cooling System Cleaner or its equivalent. The following
directions for cleaning the system applies only when this
type cleaner is used.
WARNING: If you siphon coolant from the
radiator, do not use mouth to start siphoning
action. The coolant solution is POISONOUS
and can cause death or serious illness if
swallowed.
1. Siphon coolant from the cooling system, including
the cylinder block.
2. Remove thermostat and replace thermostat housing.
3. Add the liquid portion (No. 1) of the cooling system
cleaner.
4. Fill the cooling system with water to a level of
about 3 inches below the top of the overflow pipe.
5. Cover the radiator and run the engine at moderate
speed until engine coolant temperature reaches 180
degrees.
6. Remove cover from radiator and continue to run
the engine for 20 minutes. Avoid boiling.
7. While the engine is still running, add the powder
portion (No. 2) of the cooling system cleaner and
continue to run the engine for 10 minutes.
WARNING: BE CAREFUL NOT TO SCALD
YOUR HANDS.
8. At the end of this time, stop the engine, wait a few
minutes and then open the engine block drain
cocks. Also, remove lower hose connection.
NOTE: Dirt and bugs may be cleaned out of
the radiator air passages by blowing out with
air pressure from the back of the core. Do
not bend radiator fins.
Reverse Flushing
Reverse flushing should always be accomplished after
the system is thoroughly cleaned as outlined above.
Flushing is accomplished through the system in a
direction opposite to the normal flow. This action causes
the water to get behind the corrosion deposits and force
them out.
Radiator
1. Remove the radiator upper and lower hoses and
replace the radiator cap.
2. Attach a lead-away hose at the top of the radiator.
3. Attach a new piece of hose to the radiator outlet
connection and insert the flushing gun in this hose.
4. Connect the water hose of the flushing gun to a
water outlet and the air hose to an air line.
5. Turn on the water and when the radiator is full,
turn on the air in short blasts, allowing the radiator
to fill between blasts of air.
CAUTION: Apply air gradually as a clogged
radiator will stand only a limited pressure.
6. Continue this flushing until the water from the
lead-away hose runs clear.
Cylinder Block and Cylinder Head
1. With the thermostat removed, attach a lead-away
hose to the water pump inlet and a length of new
hose to the water outlet connection at the top of the
engine.
NOTE: Disconnect the heater hose and cap
connections at engine when reverse flushing
engine.
2. Insert the flushing gun in the new hose.
3. Turn on the water and when the engine water
jacket is full, turn on the air in short blasts.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E C O O L IN G
4. Continue this flushing until the water from the
lead-away hose runs clear.
Heater Core
1. Remove water outlet hose from heater core pipe.
2. Remove inlet hose from engine connection.
3. Insert flushing gun and flush heater core. Care must
be taken when applying air pressure to prevent
damage to the core.
Fan Belt Adjustment
1. Loosen bolts at Delcotron mounting.
2. Pull Decotron away from engine until desired
tension reading is obtained with a strand tension
gauge. Refer to “Engine Tune Up Specifications” .
3. Tighten all Delcotron bolts securely.
Radiator Cap
The radiator cap should be washed with clean water and
pressure checked at regular tune-up intervals. Inspect
rubber seal on cap for tears or cracks. Install radiator
cap on tester (fig. 4). If the pressure cap will not hold
pressure or does not release at the proper pressure,
replace the cap.
Thermostat
The thermostat consists of a restriction valve actuated by
a thermostatic element. This is mounted in the housing
at the cylinder head water outlet above the water pump.
Thermostats are designed to open and close at
predetermined temperatures and if not operating
properly should be removed and tested as follows:
Replacement
6 K -9
3. Inspect thermostat valve to make sure it is in good
condition.
4. Place thermostat in a 33% glycol solution 25&deg; above
the temperature stamped on the thermostat valve.
5. Submerge the valve completely and agitate the
water thoroughly. Under this condition the valve
should open fully.
6. Remove the thermostat and place in a 33% glycol
solution 10&deg; below temperature indicated on the
valve.
7. With valve completely submerged and water
agitated thoroughly, the valve should close
completely.
8. If thermostat checks satisfactorily, re-install, using a
new housing gasket.
9. Refill cooling system.
Thermostatic Fan Clutch
Replacement
All mating surfaces (water pump hub and fan clutch
hub) should be inspected for smooth mating surfaces
and reworked as necessary to eliminate burrs or other
imperfections. Except for the fan belt, components
should be assembled to the engine (See Water Pump
Removal and Installation Procedures). Radial run-out
should be checked as follows:
1. Secure the fan blade to prevent rotation. (See
Figure 12.)
2. Mount a dial indicator (.001 graduations) to the
engine and place the indicator pointer on the fan
blade spider. Preferably on the longest band or
space on the spider. (See Figure 13.)
3. Rotate the water pump pulley in one direction and
note the total amount of indicator needle
1. Remove radiator to water outlet hose.
2. Remove thermostat housing bolts and remove water
outlet and gasket from thermostat housing (fig. 11).
Fig. 10—Pressure Checking Radiator Cap
Fig. 11—Replacing Thermostat
LIGHT DUTY TRUCK SERVICE MANUAL
6 K - 1 0 E N G IN E C O O L IN G
Fig. 13 —Checking Run-Out
Fig. 12—Securing Fan Blade
movement. This represents the total radial run-out.
Mark the point on the pulley at which the highest
reading is obtained.
4. If the total indicator reading is less than .006 inch,
the assembly is within specification. Install fan belt
and adjust.
If the total indicator run-out exceeds .006 inch, proceed
to Step 5.
5. Divide the total indicator reading in half and
obtain this thickness from shim stock (1/2 x 3/4)
and resork per Figure 8. Place this shim pack
between the water pump pulley and fan clutch hub
at the bolt closest to the point marked on the pulley
in Step 3. If the mark on the pulley is between two
bolts so that it is difficult to determine which bolt is
closest, place two shim packs; one under each bolt
on either side of the mark. (See Figure 15.)
B o lt Torque S equ en ce
a. When one shim pack is used, first, torque the
bolt over which the shim pack has been placed;
second, the bolt opposite the first; and finally,
the other two. Recommended torque is 25 lbs. ft.
b. When two shim packs are used, each bolt must
be torqued partially; then to full torque
alternating between opposite bolts; then the
other two bolts in the same manner. Recom&shy;
mended torque is 25 lbs. ft.
NOTE: Excessive run-out may result if the
above sequence and recommended torque is
not used.
6. Recheck total indicator run-out to verify that run&shy;
out is within .006 inch. Install fan belt and adjust.
Water Pump
Removal
WARNING: If you siphon coolant from the
radiator, do not use mouth to start siphoning
action. The coolant solution is POISONOUS
and can cause death or serious illness if
swallowed.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E C O O L I N G
1. Siphon coolant from the radiator and break loose
the fan pulley bolts.
2. Disconnect heater hose, radiator lower hose and by&shy;
pass hose (as required) at water pump.
3. Loosen Delcotron and remove fan belt then remove
fan bolts, fan and pulley.
CAUTION: I f a fan blade is bent or damaged
in any way, no attempt should be made to
repair and reuse the damaged part. A bent or
damaged fan assembly should always be
replaced with a new fan assembly.
It is essential that fan assemblies remain in proper
balance and proper balance cannot be assured once
a fan assembly has been bent or damaged. A fan
assembly that is not in proper balance could fail and
fly apart during subsequent use creating an
extremely dangerous condition.
NOTE: Thermostatic fan clutches must be
kept in an “in-car” position. When removed
from the car the assembly should be
supported so that the clutch disc remains in a
6K -1 1
vertical plane to prevent silicone fluid
leakage.
4. Remove pump to cylinder block bolts and remove
pump and old gasket from engine.
NOTE: On in line engines, pull the pump
straight out of the block first, to avoid
damage to impeller.
Installation
1. Install pump assembly on cylinder block then, using
a new, sealer coated, pump-to-block gasket tighten
bolts securely.
2. Install pump pulley and fan on pump hub and
tighten bolts securely.
NOTE: A guide stud (5/16&quot;-24 x 1&quot; bolt with
the head removed) installed in one hole of
the fan will aid in aligning hub, pulley and
fan. Remove stud after starting the remain&shy;
ing three bolts.
3. Connect hoses and fill cooling system.
4. Install fan belt and adjust as previously outlined.
5. Start engine and check for leaks.
D IA G N O S IS
If the radiator is filled too full when cold, expansion
when hot will overfill the radiator and coolant will be lost
through the overflow pipe. Adding unnecessary water
will weaken the anti-freeze solution and raise the
temperature at which freezing may occur.
If the cooling system requires frequent addition of water
in order to maintain the proper level in the radiator,
check all units and connections in the cooling system for
evidence of leakage. Inspection should be made with
cooling system cold. Small leaks which may show
dampness or dripping can easily escape detection when
the engine is hot, due to the rapid evaporation of
coolant. Tell-tale stains of grayish white or rusty color, or
dye stains from anti-freeze, at joints in cooling system
are almost always sure signs of small leaks even though
there appears to be no damage.
Air or gas entrained in the cooling system may raise the
level in radiator and cause loss of coolant through the
overflow pipe. Air may be drawn into the cooling system
through leakage at the water pump seal. Gas may be
forced into the cooling system through leakage at the
cylinder head gasket even though the leakage is not
sufficient to allow water to enter the combustion
chamber.
COOLING SYSTEM CHECKS
To check for exhaust leaks into the cooling system, drain
the system until the water level stands just above the top
of the cylinder head, then disconnect the radiator upper
hose and remove the thermostat and fan belt. Start the
engine and quickly accelerate several times. At the same
time note any appreciable water rise or the appearance
of bubbles which are indicative of exhaust gases leaking
into the cooling system.
Water pump operation may be checked by running the
engine while squeezing the radiator upper hose. A
pressure surge should be felt. Check for a plugged vent&shy;
hole in pump.
Test for restriction in the radiator, by warming the
engine up and then turning the engine off and feeling
the radiator. The radiator should be hot along the left
side and warm along the right side, with an even
temperature rise from right to left. Cold spots in the
radiator indicate clogged sections.
An operational check of the thermostat can be made by
hanging thermostat on a hook in a 33% glycol solution
25&deg; above the temperature stamped on the thermostat
valve. Submerge the valve completely and igitate the
solution thoroughly. Under this condition the valve
should open. Remove the thermostat and place in a 33%
glycol solution 10&deg; below temperature indicated on the
valve. With valve completely submerged and water
agitated thoroughly, the valve should close completely.
Coolant Loss
1. Make sure owner is not trying to keep radiator
filled to top, and is not filling while cold. The
expansion and contraction of water during opera&shy;
tion will cause level to drop below top of filler neck.
LIGHT DUTY TRUCK SERVICE MANUAL
6 K - 1 2 E N G IN E C O O L IN G
Once level becomes stabilized, it will not change
appreciable during operation.
2. Check for crack in block. Pull engine oil dip-stick to
check for water in crankcase.
3. Remove rocker arm covers and check for cracked
cylinder head.
4. Remove cylinder heads and check gaskets. While
heads are off, check for cracks in heads or block.
Overheating
1. Check to see that the radiator cap seats in radiator
filler neck and releases at specified pressure (15 lb.).
2. Check coolant level.
3. Check temperature sending unit and/or gauge.
4. Check engine thermostat.
5. Check fan belt for excessive looseness.
6. Check for punctures in radiator, ruptured or
disconnected hoses, loose pressure cap or use of low
boiling point antifreeze. These conditions prevent
cooling system from maintaining proper pressure.
7. Clean debris from radiator and/or condenser.
8. Check engine operation to make sure tune-up is not
needed. Improper timing may cause overheating.
9. Check for driving conditions which may cause
overheating. Prolonged idling, start and stop
driving in long lines of traffic on hot days, climbing
steep grades on hot days, etc. will occasionally cause
coolant to boil.
10. Clean cooling system.
11. Remove cylinder heads and check water passages in
heads and block for obstructions.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G IN E C O O L I N G
6K -13
Fig. 16—Overheating Chart
LIGHT DUTY TRUCK SERVICE MANUAL
6 K - 1 4 E N G IN E C O O L IN G
Fig. 17—Coolant Loss Chart
LIGHT DUTY TRUCK SERVICE MANUAL
E N G I N E FUEL
6M -1
SECTION 6M
ENGINE FUEL
CONTENTS OF THIS SECTION
Description......................................................................... 6M-1
Theory of Operation...................................................... 6M-3
Maintenance and Adjustments................................... 6M-16
Service Operations........................................................... 6M-23
Diagnosis............................................................................ 6M-42
Special Tools..................................................................... 6M-67
DESCRIPTION
This Section of the 1973 Truck Service Manual covers the
above &quot;Contents&quot; items as they relate to carburetors and
the engine fuel system. This service section also includes,
carburetor removal and installation and external
adjustments for all 10-30 series trucks, in addition to,
maintenance procedures for choke coils, throttle linkage,
accelerator and choke controls, air cleaners and fuel
filters. For carburetor identification, overhaul procedures,
assembly and disassembly of components, and internal
carburetor adjustments, refer to Section 6M, of the
Overhaul Manual, under the carburetor being serviced.
In addition to carburetor adjustment specifications, also
refer to Specifications at the end of the manual for
carburetor application and type.
Carburetors used with 10-30 Trucks are designed to
meet the particular requirements of engine, transmission
and vehicles. Carburetors that look alike are not always
interchangeable. (Refer to carburetor part number and/
or specifications). Service procedures for the various
carburetors are similar, therefore, typical illustrations
and procedures are used except where specific illustra&shy;
tions or procedures are necessary to clarify the
operation.
MODEL MV (lbbl.) CARBURETOR
The Model MV carburetor is a single bore down-draft
carburetor using a triple venturi in conjunction with a
plain tube nozzle.
Fuel flow through the main metering system is controlled
by a main well air bleed and fixed orifice jet. The power
enrichment system is used to provide good performance
during moderate to heavy accelerations.
The idle system on automatic transmission models
incorporate a hot idle compensator to maintain smooth
engine idle during periods of extreme hot engine
operation.
The Model MV carburetor has an automatic choke
system. The vacuum diaphragm unit is mounted
externally on the air horn. The choke coil is mounted on
the manifold and is connected to the choke valve shaft
by a rod.
An integral fuel inlet filter is mounted in the fuel bowl
behind the fuel inlet nut to give maximum filtration of
incoming fuel.
Other features of the Model MV include an aluminum
throttle body, and a thick throttle body to bowl insulator
gasket. The carburetor has internally balanced venting
through a vent hole in the air horn, which leads from the
bowl into the bore beneath the air cleaner.
The carburetor model identification is stamped on a
vertical portion of the float bowl adjacent to the fuel
inlet nut. If replacing the float bowl, follow the
instructions contained in the service package to transfer
the identification.
An electrically operated idle stop solenoid is used on all
MV models. The solenoid mounts on the carburetor float
bowl and replaces the normal carburetor idle stop screw.
The curb idle speed setting is made by turning the
electrically operated idle stop solenoid in the boss located
on the carburetor bowl. See &quot;Idle Stop Solenoid
Adjustment&quot;.
In the manual transmission models, the idle stop
solenoid is used along with a Combination Emission
Control (C.E.C.) valve. The C.E.C. valve, when energized
through the transmission, acts as a throttle stop by
increasing idle speed during high gear deceleration and
helps in controlling overrun hydrocarbons. The C.E.C.
valve also provides full spark vacuum advance to the
distributor during high gear operation and is de&shy;
energized in lower gears and at idle for retarded spark
timing during this period.
The idle mixture screw has a limiter cap installed and no
adjustment will be provided on the vehicle. The mixture
screw is pre-set at factory and capped and no further
adjustment is required.
An Exhaust Gas Recirculation system (E.G.R.) is used on
all applications for 1973 to control oxides of nitrogen.
The vacuum supply port necessary to operate the
recirculation valve is located in the throttle body and
connects through a channel to a tube which is located at
the top of the air horn casting. See Idle System for port
location and operation.
LIGHT DUTY TRUCK SERVICE MANUAL
I
6 M - 2 E N G IN E FUEL
MODEL 2GV (2 bbl.) SAE 1-1/4&quot;
CARBURETOR
The Rochester Model 2GV 1-1/4 (small bore 2 bbl.)
carburetor includes some of the following features.
1. A plastic float is the same as is used in the Model
2GV large bore (1 1/2&quot;) 2 barrel. Along with the
plastic float the float needle and seat assembly is
longer which improves fuel level control in the float
bowl.
A float bowl dam has been added to the float bowl
adjacent to the pump well area. The purpose of the
float bowl dam is to prevent fuel slosh and help
maintain improved fuel supply to the main metering
jets under all types of vehicle operation.
2. The pump system on the Model 2GV 1-1/4&quot;
carburetor incorporates an expander spring beneath
the pump plunger cup to maintain constant pump
cup to pump well contact.
In addition to the garter spring, a fuel inlet channel in
the bottom of the pump well maintains sufficient fuel
supply to the pump circuit at all times. A small
aluminum inlet check ball seats in the bottom of the well
so that as the pump plunger moves downward, the fuel
will be forced out through the pump jets.
3. The hot idle compensator will not be used on the
Model 2GV 1-1/4&quot; carburetors. Leaner fuel
mixtures and changes in idle speed have made the
compensator unnecessary.
4. The fast idle cam steps have improved fast idle
speed control during the warm-up period.
5. An exhaust gas recirculation system (E.G.R.) is used
on all applications, to control oxides of nitrogen.
The exhaust gas recirculation valve is operated by a
vacuum signal taken from the carburetor. A vacuum
supply tube, installed in the float bowl beneath the spark
tube, connects by a channel to two timed vacuum ports
located just above the throttle valve in the throttle body
bore.
As the throttle valve is opened beyond the idle position,
the first E.G.R. port is exposed to manifold vacuum to
supply a signal to the E.G.R. valve located on the intake
manifold. The second port in the throttle body is located
mid-way between the top of the throttle valve and the
throttle body casting and is positioned higher to act as
an air bleed for the lower port, thereby, modulating the
amount of vacuum signal supplied by it.
As the throttle valve is opened further in the part throttle
range, at higher air flows, the vacuum signal decreases at
the lower port. The upper port then ceases to function as
an air bleed and is gradually exposed to manifold
vacuum to supplement the signal at the lower port. In
this way the E.G.R. valve operation is timed for precise
metering of exhaust gases to the intake manifold, so that
just the right amount of exhaust gases can be added to
the inlet mixtures for proper control of the oxides of
nitrogen.
The exhaust gas recirculation system does not operate
during engine idle.
MODEL 2GV (2 bbl.) SAE 1-1/2
CARBURETOR
The Model 2G, 2GV (large bore 1-1/2”) carburetors include
the features:
1. The carburetors are calibrated to meet current
engine requirements.
2. The internal float bowl vent hole located in the air
horn is enlarged for improved float bowl venting
and vapor handling. As there are no external vents,
the carburetor is completely internally balanced.
3. Plastic main well inserts in the main fuel wells
provide improved fuel metering for the main
metering system. The use of the plastic main well
inserts provide improved fuel control in the off-idle,
transfer and part throttle ranges of operation.
The plastic main well inserts surround the main fuel
discharge nozzles and are removable for carburetor
disassembly and cleaning purposes.
4. An exhaust gas recirculation system (E.G.R.) is used
on all applications to control oxides of nitrogen
emissions. The vacuum supply necessary to operate
the exhaust gas recirculation valve is obtained
through timed vacuum ports in the throttle body
which connects through a channel to a tube which is
located beneath the spark tube at the side of the
float bowl.
As the throttle valve is opened beyond the idle position,
the first E.G.R. port is exposed to manifold vacuum, to
supply a signal to the E.G.R. valve located on the engine
manifold. The second port in the throttle body is located
mid-way between the top of the valve and the throttle
body casting and is positioned higher to act as an air
bleed for the lower port, thereby, modulating the amount
of vacuum signal supplied by it.
As the throttle valve is opened further in the part throttle
range, at higher air flows, the vacuum signal decreases at
the lower port. The upper port then ceases to function as
an air bleed and is gradually exposed to manifold
vacuum to supplement the signal at the lower port. In
this way, the E.G.R. valve operation is timed for precise
metering of exhaust gases to the intake manifold, so that
the right amount can be added to the inlet mixtures, for
proper control of the oxides of nitrogen.
The exhaust gas recirculation system does not operate
during the normal curb engine idle.
5. The steps on the fast idle cam have been revised to
improve engine performance during the warm-up
period.
6. A pump fill trough in the pump system is located
just beneath the venturi cluster gasket. The fill
trough is only used on passenger car models and
gives added capacity to the pump system above the
pump discharge ball for improved operation of the
pump system.
LIGHT DUTY TRUCK SERVICE MANUAL
E N G I N E FUEL
MODEL 4MV (4 bbl.) QUADRAJET
CARBURETOR
The Model 4MV carburetor has many features including
the following:
1. All models are calibrated to assist in meeting
emission requirements.
2. The highest step on the fast idle cam length
improves choke engine operation during the warm&shy;
up period.
3. An exhaust gas recirculation system is used to
control oxides of nitrogen emissions. Dual punched
ports are located in the carburetor throttle body
bore to supply a vacuum signal for operation of the
exhaust gas recirculation valve.
Two punched ports, one just above the throttle valve and
one mid-way between the throttle valve and upper
surface of the throttle body are located in the primary
bore.
As the primary throttle valve is opened beyond the idle
position, the first vacuum port for the E.G.R. system is
exposed to manifold vacuum to supply a vacuum signal
to the E.G.R. valve. To control the vacuum signal at the
6M -3
lower port, the upper port bleeds air into the vacuum
channel and modulates the amount of vacuum signal
supplied by the lower E.G.R. port. In this manner, the
E.G.R. valve can be timed for precise metering of
exhaust gases to the intake manifold dependent upon
location of the ports in the carburetor bore and by the
degree of throttle valve opening.
As the primary throttle valve is opened further in the
port throttle range at higher air flows the vacuum signal
decreases at the lower ports. At this time the upper port
ceases to function as an air bleed and is gradually
exposed to manifold vacuum to supplement the vacuum
signal at the lower port and help maintain correct E.G.R.
valve position.
The upper and lower vacuum ports connect to a cavity in
the throttle body which, in turn, through a passage
supply the vacuum signal to the E.G.R. tube pressed into
the front corner of the throttle body. The tube in the
throttle body is connected by a hose to the E.G.R. valve
located on the engine manifold.
The E.G.R. valve remains closed during periods of
engine idle and deceleration to prevent rough idle from
excessive exhaust gas contamination in the idle air/fuel
mixtures.
THEORY OF OPERATION
INDEX
Theory of Operation...................................................... 6M-3
What is a Carburetor................................................ 6M-3
Purpose of a Carburetor........................................... 6M-3
Atomization................................................................. 6M-4
Metering....................................................................... 6M-5
Air Measurement.................................................... .6M-5
Fuel Metering.......................................................... .6M-6
Venturi Principle......................................................6M-7
Distribution...................................................................6M-7
WHAT IS A CARBURETOR
A carburetor is a metering device which mixes fuel with
air in the correct proportion and delivers them to the
engine cylinders as a combustible mixture. The design of
a carburetor is based on the application of natural
principles to the job of providing compatible air-fuel
mixtures to meet exhaust emission standards and
driveability for the varying engine requirements. Just as
it is necessary to understand the range of fuel mixtures
required for each operational phase, so must the
serviceman basically understand the natural forces
applied by the design for delivery of these mixtures.
PURPOSE OF A CARBURETOR
The purpose of a carburetor on a gasoline engine is to
meter, atomize, and distribute the fuel throughout the air
Fuel-Air Requirements.............................................. 6M-8
Power vs. Economy.................................................. 6M-8
Cold Starts................................................................... 6M-9
Basic Carburetor Systems........................................ 6M-9
Float System................................................................ 6M-10
Idle System.................................................................. 6M-10
Main Metering System............................................ 6M-11
Power System.............................................................. 6M-12
Pump System.............................................................. 6M-12
Choke System............................................................. 6M-12
flowing into the engine (Fig. 1). These functions are
designed into the carburetor and are carried out by the
carburetor automatically over a wide range of engine
operating conditions, such as varying engine speeds,
load, and operating temperature.
The carburetor also regulates the amount of air-fuel
mixture which flows to the engine. It is this mixture flow
regulation which gives the driver control of the engine
speed.
Regardless of engine speed or load, the carburetor must
automatically perform its three basic functions.
The automotive carburetor is an intricate device;
however, when studied one phase at a time, the functions
of the carburetor are easily understood.
As mentioned above, the three main functions of the
carburetor are to meter, atomize and distribute the fuel.
LIGHT DUTY TRUCK SERVICE MANUAL
6 M - 4 E N G IN E FUEL
METERING
CORRECT PR O P O R TIO N S
O F FUEL A N D AIR
A T O M IZ A T IO N
SPRAY O F FINE PARTICLES
GREAT AIR C O N T A C T
DISTRIBUTION
U N IF O R M MIXTURE
DELIVERED T O M A N IF O L D
Fig. 1 -Basic Functions
ATOMIZATION
The engine’s source of fuel for power is gasoline. Before
gasoline can be used as fuel for an engine, it must be
atomized which means breaking the fuel into fine
particles so that it can be mixed with air to form a
combustible mixture. Contrary to popular belief,
gasoline in its liquid state is not combustible; only
gasoline vapor will burn. A common example of this is a
cigarette lighter which works fine indoors but then can’t
be lit after you’ve been outdoors in the cold for awhile.
At warmer temperatures, fuels vaporize quickly and so
can be ignited easily but at lower temperatures,
evaporation is slower and accordingly ignition is
impossible or, at least, difficult because of insufficient
vapor.
While this analogy is quite simple, it is an illustration of
the basic problems of carburetor design; that is, the
provision of combustible fuel mixtures over a broad
range of temperature and operating conditions. The
complexity of design problems continues to mount each
year due to a constant effort to reduce exhaust emissions
and at the same time improve operating conditions.
To be combustible, gasoline must vaporize. Vaporization
is the act of changing from a liquid to a gas and this
change of state occurs only when the liquid absorbs
enough heat to boil. This is what happens in a tea kettle
to change water to water vapor, or steam. Heat is
transferred to the water, raising its temperature until it
finally reaches the boiling point, at which time the water
changes to steam and is carried off to atmosphere in this
gaseous form. At seal level, the water will oil at 212&deg;F
but at high altitudes, less heat is required for water to
boil due to lower atmospheric pressure. This is known as
the temperature-pressure relationship; that is, as the
pressure is reduced, the boiling point is reduced. This
law, combined with a process known as atomization, has
important applications in the transformation of liquid
gasoline to a capor for use in combustion.
In a carburetor (Fig. 2), gasoline is discharged into the
incoming air stream as a spray and the spray is then
atomized, or torn into fine droplets to form a mist. The
resulting air-fuel mixture is drawn into the intake
manifold. At this point, the change of state occurs and
the fuel &quot;mist&quot; vaporizes as the result of several factors.
Since the pressure in the intake manifold is far less than
atmosphere, the boiling point of the gasoline is lowered
considerably. At this reduced pressure, latent heat
absorbed from the many air particles surrounding each
fuel particle causes some vaporization, which is further
aided by heat on the intake manifold floor.
Because complete fuel vaporization is the result of many
factors (ambient temperature, fuel temperature, mani&shy;
fold vacuum, and intake manifold temperature), it is
easy to see that anything which reduces any one of these
factors will adversely effect vaporization and thus reduce
fuel economy and increase exhaust emissions. Some
examples would be cold weather, an inoperative exhaust
heat control valve, and high overlap camshafts and/or
heavy throttle demands. While the effects from lower
temperatures are obvious, reduction of manifold vacuum
either by valve timing or heavy throttle operation are
highly detrimental to fuel economy due to the higher
pressures (and boiling points) resulting in the intake
manifold which reduces the amount of fuel vaporization
which will occur by the time the charge enters the
combustion chamber. Fuel not vaporized at the time of
induction is, to a large extent, exhausted unburned from
the combustion chamber and can cause high hydro&shy;
carbon exhaust emissions.
We know that gasoline, for combustion, must be
vaporized or as the change of state can be loosely
considered, absorbed by air. However, this requirement
LIGHT DUTY TRUCK SERVICE MANUAL
E N G I N E FUEL
6M -5
is further limited by the amount of air that the fuel
vapor is absorbed by. Combustible mixtures in an engine
are limited by the following proportions, or ratios, of air
to gasoline: eight parts air to one part gasoline is the
richest mixture that will fire regularly and a mixture of
18 1/2 parts air to one part gasoline is the leanest
mixture that will fire without missing in an engine.
Mixtures leaner than 18.5:1 tend to cause misfire. From
an automotive standpoint these ratios represent the
mixture extremes that an engine can tolerate, but these
limits do not provide the two conditions most sought.
The most desired ratios are a mixture that will produce
the most power per pound of gasoline and a mixture that
will provide the best economy or most miles per pound
of fuel with the least exhaust emissions.
For those who may be wondering why we are speaking
in terms of &quot;pounds&quot; of fuel instead of our more usual
gallon measure, let’s take a moment for clarification.
Actually the reason we speak in terms of pounds rather
than gallons is so that the ratio, or air-fuel mixture
proportion, terms can be smaller numbers. For example,
for most efficient (and economical) combustion, 9000
gallons of air are required to burn one gallon of
gasoline, hence an air-fuel ratio of 9000:1 by volume.
Obviously, proportions with such numerical differences
would be difficult to comprehend and extremely awkward
to work with for experimentation and design.
By using weight as the base, let’s make the same
comparison (Fig. 3). A gallon of gasoline weighs about
six pounds whereas 100 gallons of air are needed to
produce one pound of air. Converting our volume airfuel ratio to weight, we find that 9000 gallons of air
weighs 90 pounds (100 gals, equals 1 lb., therefore 9000
divided by 10090 lbs.) and one gallon of gasoline weighs
6 pounds. 90 divided by 6 equals 15 therefore we arrive
at an air-fuel ratio of 15:1 by weight.
METERING
Good combustion demands a correct mixture ratio
between fuel and air. To release all possible energy by
combustion, the right amount of fuel must be mixed with
a given amount of air. The metering job of the
carburetor is to furnish the proper air-fuel ratio for all
conditions, so that the engine operation will neither be
too lean for power requirements nor too rich for
economy (Fig. 4), while still meeting prime requirements
of low emissions.
AIR MEASUREMENT
Air flow through a pipe will create a pressure drop
within the pipe proportional to the speed of the air.
Thus, for a given pipe size, the pressure difference
between the outside air and the pressure within the pipe
provides a direct means of measuring the amount of air
flowing through the pipe.
The simplest means of measuring the pressure difference
between atmosphere and the pressure inside the pipe, is
to insert a U-tube partially filled with water into the pipe
as illustrated (Fig. 5). Since one end is open to
atmosphere, the water level will rise on the low pressure
(or pipe side) because water will flow toward an area of
lower pressure. Actually, the water is being pushed into a
state of balance by the weight of the air at the end of the
U-tube open to atmosphere vacuum. A common example
of the force exerted by the weight of air is a drinking
straw (Fig. 6). As you suck on a straw, the air within the
straw is removed, thus creating a low pressure or
vacuum. The weight, or pressure, of the air on the
surface of the liquid in the glass then forces the liquid
up the straw to fill the void. The important thing to
LIGHT DUTY TRUCK SERVICE MANUAL
6 M - 6 E N G IN E FUEL
more convenient valve for measuring the larger pressure
differences.
FUEL METERING
DEPRESSION
(LOWER PRESSURE)
WATER
Fig. 5 -Air Flow Measurement
understand is that fluid is not pulled by the vacuum but
is rather pushed into the vacuum or low pressure area by
the weight of the air pressing on the surface of the
liquid.
The difference in pressure, or vacuum, is expressed by
measuring the distance between the two heads of water
in the U-tube, or inches of water. Low vacuum is
generally expressed in inches of water but higher
vacuum, such as manifold vacuum, is usually measured
in inches of mercury because mercury is approximately
13 1/2 times heavier than water and thus provides a
As shown in measurement of air flow with the U-tube,
fluids flow when there is a difference in pressure and will
always flow toward the lower pressure. If the fluid level
in the U-tube were higher, the reduced pressure within
the pipe would cause the fluid to flow into the pipe.
Further, if a means were provided to maintain the fluid
level at a desired height in the U-tube, the amount of
fluid flow would be proportional to the pressure
difference caused by the air flow through the pipe.
Carburetors operate on the basic principle of pressure
difference.
A basic carburetor is an adaptation of the U-tube (Fig.
7). The fuel side, open to atmospheric pressure, inside of
air cleaner (internal venting), is enlarged to create a
reservoir and fitted with a float valve to maintain a
constant level of fuel. To control the quantity of fuel
delivered, a jet or metering orifice is screwed into the
base of the main nozzle. A streamlined restriction,
known as a venturi, is added to the air intake side to
create an additional pressure drop for a given rate of air
flow, dictated by upper diameter of the pipe. Finally, a
throttle valve is added to control the volume of air-fuel
mixture admitted.
Applying the basic carburetor to an engine, air flow is
initiated by the pumping action of the pistons and the
intake and exhaust valve action. As the piston moves
downward during the admission or intake stroke, the
inlet valve is open causing air to rush in through the
carburetor and manifold to fill the space left by the
downward piston travel. At engine operating speeds,
especially with multi-cylinder engines, the air flow
through the carburetor is nearly constant. The amount of
air flow, and accordingly the fuel picked up, is controlled
by the opening allowed by the throttle valve.
VENTURI
P y /..
ii
LOW PRESSURE
(VACUUM) DEVELOPED
INSIDE MOUTH
j!
THROTTLE
Fig. 6 -Vacuum Principle
Fig. 7 -Basic Carburetor
LIGHT DUTY TRUCK SERVICE MANUAL
E N G I N E FUEL
VENTURI PRINCIPLE (FIG. 8)
To obtain a greater pressure drop at the tip of the nozzle
to cause the fuel to flow, the principle of increasing the
air velocity to create a low pressure area is used. A
device called the &quot;venturi&quot; is used to increase the air
velocity and lower the pressure at the discharge nozzle.
The increased pressure differential between that of the
fuel bowl and at the carburetor throat increases fuel flow
sufficiently, at a given air flow, so that the resulting airfuel proportions result in a combustible mixture.
For example, a carburetor with a 1 1/2&quot; pipe will supply
the volume of air required for a given displacement
engine. However, the pressure drop within the carburetor
throat is insufficient to cause enough fuel to flow into the
carburetor at the desired speed to create a combustible
fuel mixture due to the large weight difference between
air and gasoline. By necking down the inner diameter of
the carburetor throat into a venturi, the air flow is forced
to speed up at the restriction area, thus further reducing
air pressure and increasing fuel flow proportionately to
achieve the desired mixture.
To be most effective, the venturi must be designed for a
certain curvature and length. The venturi design can be
tailored to provide fuel flow under any condition of air
flow. However, a small venturi may restrict high speed
engine operation and a large venturi will not provide
enough pressure differential for low speed operation. The
production venturi size is usually a compromise to
provide adequate low and high speed operation.
The carburetor discharge nozzle is located in the center
of the venturi throat to take advantage of the maximum
ATMOSPHERIC
6 M -7
pressure drop and promote atomization of the fuel. The
large venturi, cast in the carburetor bore, is called the
primary or main venturi.
Most carburetors use a primary and one or most boost
venturis. The boost venturi is usually located over the
primary with its discharge end in the low pressure area
of the primary. The purpose of the boost venturi is to
further lower the pressure at the nozzle. Additional boost
venturis may be used for finer control of pressure drop
but at high speed they tend to restrict air flow to the
engine.
Because actual venturi size is a compromise, two- and
four-barrel carburetors are used where requirements are
extreme. A two-barrel carburetor allows use of smaller
venturi for improved low speed operation yet gives
relatively good high speed operation due to the larger
throttle area provided by the two throttle valves. The
primary side of a four-barrel carburetor is designed
much the same as the two-barrel carburetor with small
venturi for low speed economy. The secondary side of a
four-barrel carburetor uses large bores and venturi for
extremely good high speed breathing. The secondary
side of the four-barrel carburetor operates only at high
degree primary throttle openings or when performance
is required.
DISTRIBUTION
For good combustion and smooth engine operation, the
air and fuel must be thoroughly and uniformly mixed,
delivered in equal quantities to each cylinde