Steering
Steering
Overview
This section will address those parts of the steering system related to the:
• Steering wheel
• Steering column
• Power steering fluid requirements
• Steering gear (TAS 55)
• Hydraulic steering pump
• Pitman
• Drag link
• Tie rod (cross tube)
• Tie rod ends
• Lubrication requirements
Appendixes In This Chapter
Appendix 1. TAS Steering Gear (Exerpt). This four page exerpt from TRW’s Steering
Gear Service Manual includes fluid information, an exploded parts diagram, and
torque specifications for the TAS55 steering gear.
Appendix 2. Popped Adjustment. This four page TRW Service Bulletin explains onvehicle poppet readjustment procedure.
Appendix 3. TRW Steering Maintenance. This TRW publication, entitled Chart Your
Way To Easy Steering, provides a solid overview of potential steering problems, their
diagnosis and correction.
[Warning] Hydraulic fluid must be handled, stored and disposed of in a
manner consistent with all the applicable local, state, and federal guidelines
concerning hazardous materials.
The hydraulic pump for the power assist is located on the engine. The configuration
of piping from the pump to the steering gear is dependent on whether the bus has
hydraulic brakes or an air brake system.
On Visions equipped with air brakes, the power steering fluid flows to the steering gear, and returns directly to the reservoir. On Visions equipped with hydraulic
brakes, the power steering fluid flows from the reservoir into the power steering
gear. The pressurized fluid is then directed to the hydraulic brake power assist
(booster). From there, the power steering fluid is returned to the reservoir, under
lower pressure.
Torque from the steering wheel is transmitted through the steering column to
the steering gear. The TAS 55 steering gear assists the efforts of the driver.
821
[Caution] The power steering fluid and the brake fluid are not the same.
They must be kept separate. Use DOT–3 for the brake system and use Dexron III
for the power steering fluid.
TRW STEERING
MAINTENANCE
POPPET
ADJUSTMENT
TAS
STEERING GEAR
3
2
1
APPENDIX
APPENDIX
APPENDIX
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Other oils are acceptable for the power steering system; however, the system must
be drained and flushed to use any of these. (See the appropriate TRW Service Manual
for a complete list.) Do not mix oils or fluids if you change the fluid.
The reservoirs are mounted on the firewall, near the steering column. The brake
reservoir has two filler caps, and stands away from the firewall due to the electrically
operated emergency brake boost pump assembly.
Steering System Maintenance
Before attempting to work on the steering gear, or any portion of the steering system, you must stabilize the vehicle. Read and understand the Warnings and Cautions
in the General Maintenance chapter of this manual.
Regularly check the fluid fluid level in the power steering reservoir. Change the
fluid and replace the filter at the intervals specified in the Specs & Maintenance chapter. Clean around the reservoir filler cap before removing it. Dirt and other foreign
matter can damage the hydraulic system.
Do not bend or straighten any steering component or linkage. Never attempt
to weld any broken steering component. Do not use a torch to remove any steering
component. Use only original equipment replacement parts.
Never use high pressure or steam to clean the power steering gear while on or off
the bus. Doing so can force contaminants inside the gear and lead to malfunction.
Proper alignment of the steering column is important to assure smooth steering.
Correct the cause of any free play, rattle, or shimmy immediately to avoid damage
to the steering system. Record and report any malfunctions or accidents which may
have damaged steering components.
Axle Stop Adjustment
Adjustment of the axle stops should be made after tow-in has been set on the front
axle.
822
1. With the front tires on turn-angle plates, center the left front tire in the
straight ahead position using alignment equipment, then set the turn-angle
plates to zero.
2. Set the axle stops to allow 50° of full right and full left steerage. Check for
adequate clearance between tires and wheelwells. Lock the axle stop jam
nuts after adjusting the axle stops.
3. Remove the turn-angle plates. Verify that the axle stops contact the axle pads
at full right-hand and left-hand turns. It may be necessary to relieve tire flex
by rolling the bus forward or backward, in order to make the axle stops contact. There must be at least 1/4-inch clearance between the pitman arm, drag
rod and front axle tie rod, and all potential interference points.
Setting the Steering Poppets
To adjust the steering poppets, refer to Appendix 2 in this chapter.
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Toe-In Adjustment
Set the toe in with no weight in the bus. The curb weight of the vehicle should be
on the ground. Toe should be checked at the tires front and rear center, at a distance
above the ground equal to the rolling radius of the tires. The toe must be 1/16 ± 1/32
(.06” ± .03”).
1. Adjust the toe by turning the tie rod cross tube.
2. When the correct toe is achieved, tighten the pinch bolts at the tie rod ends.
Torque the pinch bolts to 50–60 ft. lbs. (67.79–81.35 Nm).
Steering Lubrication Points
Use NLGI #2 EP and greases rated GC–LB, or equivalent. Refer to the Specs & Maintenance chapter for service intervals.
• The steering gear. (Use only hand grease gun to lube the steering gear.)
• Both ends of the draglink.
• Top and bottom of the King-pin.
• Both ends of the tie-rod.
• The slack adjuster.
• The cam brake housing.
King-Pin Lubrication
The suspension must be loaded prior to lubrication. Either place the bus on the
ground or lift by the wheels; not the axles.
1. Clean off all the grease fittings with clean shop towel prior to lubrication.
2. Lubricate the King pins through the fittings at the top and bottom of the
King pin.
3. Force the proper lubricant into the upper and lower grease fittings until
grease flows from the purge locations. Greasing at the lower zerk should
purge lubricant from the thrust bearing shell. The right hand side (curb side)
of the axle has a steel roller thrust bearing; the left hand side has a composite
thrust bearing. Both purge in the same area.
823
King Pin Grease Purge Locations
Tie-Rod Lubrication
1. Turn the bus wheels straight ahead.
2. Clean the zerk fittings at each end.
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3. Wipe the seal/boot clean as well.
4. Attach a grease gun to the zerk fitting. Either a hand or air operated grease
gun may be used. If an air operated grease gun is used, the system air pressure should not exceed 150 psi (1035 kPa).
[Caution] Exceeding the maximum air pressure specification, can cause
damage to the dust boot, leading to premature component failure.
If the Rod-end will not accept lubricant:
4.1 Remove the zerk fitting.
4.2 Inspect the threaded zerk fitting hole in the tie-rod end and remove
any obstructions.
4.3 Install a new zerk fitting if necessary.
4.4 When the fitting accepts lubrication as required, continue with the
procedure.
5. If the tie rod will not accept grease after replacing the zerk fitting, the tie rod
end must be replaced. Refer to the Tie Rod section in this chapter, and to the
Hendrickson SteerTek manual which is included as an appendix in the Front
Axle & Suspension chapter.
6. Continue to lubricate until all fittings in the steering system are purged of old
grease.
Steering Wheel & Switches
824
Steering Wheel & Switch Removal
The hub of the steering column contains the horn connection, the turn signal self
cancel mechanism, the dimmer switch for the headlights and the hazard flasher
switch. To access these components, it is necessary to remove the steering wheel.
1. Using a small thin tool, such as small screwdriver, carefully remove the horn
button from the center of the steering wheel.
2. Remove the large hexnut securing the steering wheel to the steering column.
3. Using a wheel puller of the proper size and shape, remove the steering
wheel.
4. Remove the four, ¼-inch, hexhead screws.
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5. Using a small thin tool, carefully separate the two pieces of the steering column housing. Be very careful to avoid breaking the wires.
6. Remove the grounding wire from the lower steering column hub.
7. Disconnect the wiring harness from the switch.
8. Remove two screws from the underside of the hub and carefully remove the
switch assembly. It is recommended that the whole switch assembly be replaced, not repaired. Contact Blue Bird Parts Sales, or your Blue Bird Distributor, for replacement information.
Steering Wheel & Switch Reinstallation
To replace the switch/wheel assembly, reverse the procedure above.
1. Replace the ¼-inch hexhead screws that secure the switch assembly to the
steering column assembly. Torque them to 2–4 ft. lbs. (2.71–5.42 Nm).
2. Connect the wiring harness to the switch.
3. Position the top section of the steering column housing over the lower section and snap into place.
4. Install the four ¼-inch hexhead screws. Torque them to 2–4 ft. lbs. (2.71–5.42
Nm).
• Ensure the turn indicator lever operates in the normal manner.
• Check the hazard flasher operation.
• Check the Headlight dimmer toggle switch for proper operation.
5. Ensure that the front wheels are pointed straight ahead.
6. Ensure the steering wheel is positioned properly.
825
7. Press the hub of the steering wheel into position over the spline at the end of
the steering column shaft.
8. Install the retainer nut at the end of the steering shaft. Torque to 55–65 ft.
lbs. (75.57–88.13 Nm). If the threaded end of the steering shaft is not flush
with the nut; remove the nut, clean the threads of the nut and the shaft. Then
apply 3 drops of Loctite™ (242 blue) or equivalent, and nstall and torque the
nut.
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Steering Column & Intermediate Steering Shaft
Steering Column Removal
1. Remove the pinch bolt securing the steering column shaft to the intermediate steering shaft assembly, and collapse the shaft to separate the assembly.
2. Remove the lower four nuts securing the steering column assembly to the
firewall, inside the bus.
3. Disconnect the three harness connectors located behind the dash above the
steering shaft housing.
4. Remove the four upper bolts and nuts securing the steering column to the
under side of the dash.
For questions regarding the repair of the steering column assembly, refer to the appropriate Ross service manual.
Steering Column Reinstallation
1. Position the steering column assembly so that the four bolts and nuts that
secure the column to the dash mounting bracket can be loosely installed.
2. The installation procedure is now essentially the reverse order of the removal
steps above, with the exception that the wiring harness should not be connected until the last step to avoid possible damage.
3. Torque the four nuts at the firewall to 2–4 ft. lbs. (2.71–5.42 Nm).
826
4. Torque the four 3/8 bolts securing the steering column to the dash to 10–15
ft. lbs. (13.56–20.34 Nm).
5. Slide the intermediate steering shaft assembly into position. Torque a new
cad/wax locknut to 40.32–43.68 ft. lbs. (54.66–59.22 Nm).
Intermediate Steering Shaft Removal
To remove the intermediate (telescoping) steering shaft:
1. Remove the 7/16 bolt at the steering column end of the shaft.
2. Remove the 7/16 bolt at the steering gear end of the shaft.
3. Collapse the shaft to remove it from the spline at each end.
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Steering Gear
The TAS 55 is an integral hydraulic power steering unit. The steering gear contains a
manual steering mechanism, a hydraulic control valve, and a hydraulic power cylinder. The control valve senses the steering gear requirements and directs fluid to the
appropriate cylinder cavity at the proper flow rate and pressure.
The speed at which the driver can turn the steering wheel with power assist is
dependent upon the rate of flow provided by the hydraulic pump. (Minimum flow
rate is 2.6 gpm.) As the driver turns the steering wheel faster or slower, more or less
fluid is required by the gear. The pressure of the hydraulic fluid is used to overcome
the resistance at the tires. The higher the pressure, the more work it can perform.
(Maximum operating pressure is 2,175 psi.)
The steering gear is connected to the steering gear input shaft. The input shaft is
connected to a worm shaft. When the driver turns the steering wheel, the input shaft
and worm shaft rotate. The worm shaft is in turn connected to a rack piston through
the recirculating ball mechanism. This rotational movement moves the rack piston
axially in the gear housing cylinder bore. The rack piston turns the sector shaft, which
is connected by linkage to the steering wheels.
Pressurized fluid assists the movement of the rack piston, reducing the effort needed to steer the bus. As the input shaft is turned, the control valve spool
mounted on the torsion shaft (the torsion shaft connects the input shaft to the worm
shaft) shifts and sends pressurized fluid to either side of the rack piston. A relief
valve, mounted on the valve housing, limits maximum supply pressure to protect the
power steering gear. This is the primary pressure protection for the steering system.
(A secondary pressure relief valve is located in the hydraulic pump assembly.)
Objectionable kickback is prevented due to the geometry of the steering gear. If
the wheels receive a shock load, it is transmitted back through the sector shaft, rack
piston, and worm gears. This load is neutralized by the control valve, which sends
high pressure fluid to the correct side of the rack piston to resist the shock forces. By
absorbing the shock forces hydraulically, the steering gear prevents objectionable
kickback at the steering wheel.
The steering gear is equipped with two poppet valves, one on each side of the
rack piston. The poppet valves are set to the axle stops, after axle stop adjustment
has been made. When the steering wheels are turned and approach the axle stop,
one poppet valve (depending on the direction of turn) trips. The tripped poppet
valve opens, allowing fluid to pass the piston, which reduces pressure in the gear
and helps reduce heat generated by the pump. At the same time, the valves also
reduce forces on the steering linkage.
Careful preliminary checks should be done to identify a steering problem and its
symptoms before deciding to tear down the steering gear. In most cases, the steering gear should be the last component suspected as cause of a steering problem.
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Steering Gear Removal
It is not necessary to completely remove the intermediate
steering shaft to remove the steering gear.
1 Ensure the front wheels are straight ahead.
2 Exercise care that all applicable local, state and federal
laws are observed, and drain the power steering fluid
(Dexron III) into an acceptable container for disposal.
3. Remove the 7/16 bolt from the steering gear end of the
intermediate steering shaft coupler.
4. Separate the intermediate steering shaft from the steering gear, and then secure it safely out of the way.
7/16 Coupler Bolt
Hydraulic Hose Connections
5. Remove the hydraulic hoses. Be sure to note which hose is installed at which
port on the steering gear, for installation. Be ready to contain hydraulic fluid
escaping as the hose fittings are opened and removed.
6. Remove the cotter pin and the castle nut at the lower
(drag link) end of the Pitman arm. Discard the cotter
pin. Secure the drag link in a manner to protect the
journal surface.
[Warning] Proper support is required to continue these
instructions. The steering gear may weigh as much as 110
pounds (49.895 kg).
828
6. Remove the 3 mounting bolts from the steering gear.
Notice that the forward top bolt is inside and forward
of the front crossmember. Do not remove the 2 smaller
bolts near this position.
Steering Gear Reinstallation
Installation of the steering gear is accomplished in the reverse order of removal. Always use new hardware when installing steering assembly components. Be sure the
long mounting bolt, Blue Bird Part Number 0059401 (3/4 –10 X 6 1/4), is installed at the
bottom-center position. The top mounting bolts are Blue Bird Part Number 1021815
(3/4–10 X 41/2). These bolts are Grade 8 and the locknuts are Cad/Wax. The flat washers must be hardened as well. Contact your Blue Bird distributor for replacement
hardware.
The top mounting bolts (the shorter ones) should be installed with the bolt
hexhead inside the frame rails. The bottom-center bolt should be installed with the
bolt hex-head outside the frame rails. Torque the mounting bolts to 250–282 ft. lbs.
(339–382 Nm).
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Steering Gear Mounting Bolts
Castle Nut & Cotter Pin
steering
Carefully thread the hydraulic fittings to the proper port. Installing them incorrectly will cause damage to the steering gear and, possibly, the hydraulic pump.
Tighten the flare fittings to 11/2 turns past finger tight. Ensure that the fitting is held at
the hex flats as the fittings are tightened. Do not apply excessive torque to the fitting
to steering gear connection. There is an “O” ring in the connection. Route, and secure,
all hoses and tubing to provide at least ½ inch clearance from any moving part.
Pitman Arm
Pitman Arm Removal
Remove the Pitman arm end of the draglink and secure it safely out of the way. Then
remove and discard the nut and bolt assembly from the upper end of the Pitman. Being very careful of the spline on the steering gear, remove the Pitman arm by pulling
with a wheel puller.
Pitman Arm Installation
1. Position the Pitman arm so that the index mark aligns with the mark on the
output spline of the steering gear.
2. The Pitman arm offset must be inward, and at the bottom.
3. Press the Pitman onto the output spline of the steering gear.
4. Install new hardware (3/4–10 Grade 8), and torque to 250–282 ft. lbs. (339–
382 Nm).
5. Attach the drag link to the Pitman arm. Position the drag link journal into the
lower hole in the Pitman. Torque the castle nut to 110–125 ft. lbs. (149.14–
169.48 Nm), then align a castle nut slot with the cotter pin hole. If necessary,
tighten further just enough to align. Install a new cotter pin and bend each
end at least 45° to hold it in position.
829
Drag Link
Drag Link Removal
1. Remove and discard the cotter pin from the castle nut on the each end of the
drag link.
2. Remove the castle nut from the Pitman arm end and secure the drag link.
3. Remove the castle nut from the axle end of the drag link, and then remove
the drag link journal from the Pitman arm. Be sure to wrap and protect the
journal surfaces of the draglink.
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Drag Link Reinstallation
Ensure the bend in the drag link is toward the front of the vehicle. Installation then
becomes the reversal of the removal instructions, above. Torque each castle nut to
110–125 ft. lbs. (149.14–169.48 Nm), then align a castle nut slot with the cotter pin
hole. Tighten further just enough to align if necessary. Install a new cotter pin and
bend each end at least 45° to hold it in position.
Refer to the Hendrickson™ SteerTek service manual included as an appendix to
the Front Axle & Steering chapter for further information regarding removal and installation of steering axle suspension components. Additional information is available at Hendrickson’s website at www.hendrickson-intl.com.
Tie Rods
Tie Rod Assembly Removal
If the boot on the tie rod end is damaged, replace the tie rod.
Ackerman Arm
Pinch Bolt
1. Position the steer axle straight ahead.
2. Remove and discard the cotter pins from the castle nuts
on the tie-rod knuckles.
3. Support the tie rod cross tube and remove the castle
nuts.
4. Lightly tap on the side of the steering knuckle arm to
loosen the tie rod end from the Ackerman arm.
5. Remove and discard the boot.
830
Tie Rod Assembly Installation
Installation is performed in the reverse order of the removal instructions, above.
1. Place a new boot on the tie rod end.
2. Install the tie rod journal into the Ackerman arm.
3. Torque the castle nuts to 185 ft. lbs. (250.83 Nm).
4. After torque value is achieved, tighten further just enough to align a castle
nut slot and the cotter pin hole in the tie rod journal.
5. Install a new cotter pin. Bend each leg of the cotter pin at least 45°.
Threads extend past slot
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Tie Rod End Removal
1. Remove the desired tie rod from the steering knuckle in accordance with the
instructions above, Tie Rod Assembly Removal.
2. Loosen the pinch bolt.
3. Count the turns (threads) as you remove the tie rod end from the cross tube.
Tie Rod End Installation
1. Apply anti-seize compound to the threads.
2. Install the tie rod end into the cross tube the same number of turns counted
during disassembly.
[Warning] It is critical that the threaded portion of the tie rod end extends
past the slots in the tie rod cross tube.
3. Assemble the opposite end of the cross tube assembly, if necessary.
4. Apply NLGI #2 EP grease to the journals.
5. Install the tie rod end journal into the Ackerman arm. Keep the threads dry.
6. Install the dry castle nut onto the threads of the tie rod journal. Do not lubricate the threads.
7. Torque to 185 ft. lbs. (250.83 Nm).
8. Tighten further, enough to install a new cotter pin.
831
9. Bend each leg of the cotter pin at least 45° to hold it in position.
10. Lubricate the tie rod ends with NLGI #2 EP grease. Force lubricant into the
zerk until all the air is purged.
11. Proceed with the toe-in adjustment before tightening the pinch bolts at the
tie rods.
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Steering Pump
The hydraulic pump on the Blue Bird Vision is a TRW™ PS221616L11301 if the unit has
air brakes or PS221616L21301 with hydraulic brakes.
When troubleshooting, it is important to remember to always do the simple
steps first. Look for obvious signs of leaking, component wear or damage, and hose
problems, before removing the power steering pump.
Using a flow meter, determine whether the pump is providing the necessary flow.
The steering pump should provide a flow of at least 2.6 gallons per minute (GPM). It
is recommended that you use a Power Steering System Analyzer (PSSA) to assist in
the diagnosis of steering system problems.
For details on troubleshooting the steering system, see Appendix 3 in this chapter.
Steering Pump Removal (Vision With Air Brakes)
1. Drain the system of fluid in a manner consistent with all local, state and federal laws. Wear protective gear when working with hydraulic fluids including
eye protection.
2. Remove the supply hose (17).
3. Remove the pressure line (16) from the fitting (18) at the output port of the
pump.
4. Secure the pressure line safely out of the way.
5. Remove two M10 capscrews from the hydraulic pump mounting flange.
6. Remove and discard the gasket. (Blue Bird Part Number 1360411, Gasket Hydraulic Pump).
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Steering Pump Reinstallation (Vision With Air Brakes)
Installation is accomplished in the reverse order of the removal instructions. Always
install a new hydraulic pump gasket (Blue Bird Part Number 1360411). Also install
a new split ring lock washer and torque the mounting capscrews to 53–58 ft. lbs.
(71.86–78.64 Nm).
Ensure the system is full of fluid before starting the engine. After filling the reservoir, start the engine and turn the steering wheel one direction and then the other
direction a couple of times; then stop the engine and fill the reservoir. Perform this
cycle until the system remains full.
Test drive the bus and let the power steering fluid warm to operating temperature; then check the fluid level again. Check for leaks in the system.
steering
Steering Pump Removal (Vision With Hydraulic Brakes)
1. Drain the system of fluid in a manner consistent with all local, state and federal laws. Wear protective gear when working with hydraulic fluids including
eye protection.
2. Remove the supply hose.
3. Remove the pressure line from the fitting at the output port of the pump.
4. Secure the pressure line safely out of the way.
5. Remove two 3/8 Grade 8 capscrews from the hydraulic pump mounting
flange.
6. Remove and discard the o-ring. (Blue Bird Part Number 0064251).
Steering Pump Reinstallation (Vision With Hydraulic Brakes)
Install the pump in the reverse order of the removal. Ensure that a new o-ring is
installed (Blue Bird Part Number 0064251). Install a new split ring lock washer and
torque the mounting capscrews to 29–33 ft. lbs. (33.32–44.74 Nm).
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Pump
Torque to
70 lbs./ft
Torque to
42 lbs./ft
Hydraulic Cooler Located at Lower Front Radiator
Hydraulic Reservoir
Torque Hose Ends
to 38 lbs./ft.
834
Torque Steering
Gear Fittings to
42 lbs./ft
Steering Gear
Steering Diagram with Air Brakes
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Pump
Torque to
70 lbs./ft
Torque Hose Ends to 38 lbs./ft.
Torque to
42 lbs./ft
Hydraulic Cooler Located at Lower Front Radiator
Master Cylinder
Hydraulic Reservoir
Torque Steering
Gear Fittings to
42 lbs./ft
Steering Gear
835
Steering Diagram with Hydraulic Brakes
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Torque to 20-25 (lbs./ft.)
Torque to 40-44 (lbs./ft.)
Torque to 170-180 (lbs./ft.)
Torque to 40-44 (lbs./ft.)
Torque to 115-120 (lbs./ft.).
Then tighten to next castle
nut slot if necessary.
836
Torque to 170-180 (lbs./ft.)
00054670l
Torque to 115-120 (lbs./ft.).
Then tighten to next castle
nut slot if necessary.
Steering Linkage
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Approved Hydraulic Fluids
Automatic Transmission Fluid Dexron II
Automatic Transmission Fluid Type "E" or "F"
Chevron 10W-40
Chevron Custom 10W-40 Motor Oil
Chevron Torque 5 Fluid
Exxon Nuto H32 Hydraulic Fluid
Fleetrite PSF (Can #990625C2)
Ford Spec. M2C138CJ
Mack EO-K2 Engine Oil
Mobil ATF 210
Mobil Super 10W-40 Motor Oil
Premium Blue 2000 - SAE 15W-40
*Shell Rotella T30W
*Shell Rotella T SAE 30
Texaco 10W-40
Texaco TL-1833 Power Steering Fluid
Union 10W-40
Union 15W-40
Unocal Guardol 15W-40 Motor Oil
The steering system should be kept filled with one of the above fluids. Fluids marked with an asterisk (*) have not
been approved for use with TRW's pump.
Completely flush the steering system with one of the recommended
fluids above only. Do not mix oil types. Any mixture or any unapproved
oil could lead to seal deterioration and leaks. A leak could ultimately cause the loss of fluid,
which could result in a loss of power steering assist.
Specification Numbers
The steering gear
specification number and
date code are stamped on a
machined surface opposite
the input shaft of every TAS
gear. Newer gears include a
serial number.
Spec. No
Step Bore Identifier
TAS65001A
29097S01B27
Date Code
Serial Number
An example date code
would be 29097; this means
the gear was built on the
290th day of 1997.
837
An "A" included at the end of
the specification number
indicates a step bore
housing.
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APPENDIX
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Torque Chart
Part Name
838
Item # Torque Range Dry
Auxiliary cylinder plug
54
25-35 lbf•ft (34-48 N•m)
Ball return guide cap/strap bolts
31
14-22 lbf•ft (19-29 N•m)
Bearing adjuster
17
11-15 lbf•ft (15-20 N•m)*
Locknut
18
101-122 lbf•ft (137-165 N•m)**
Manual bleed screw
50
40-50 lbf•in. (3.1-3.7 N•m)
Plug, auto bleed
51
38-58 lbf•ft (52-79 N•m)
Poppet sleeve assembly
22
16-20 lbf•ft (22-27 N•m)
Poppet sealing nut, service
60
33-37 lbf•ft (45-50 N•m)
Poppet fixed stop screw
52
38-42 lbf•ft (52-57 N•m)
Poppet fixed stop screw
52A
38-58 lbf•ft (52-79 N•m)
Relief valve cap
56
25-35 lbf•ft (34-48 N•m)
Sector shaft adjusting screw jam nut
47
40-45 lbf•ft (54-61 N•m)
Side cover bolts (TAS40)
48
108-128 lbf•ft (147-174 N•m)
Side cover bolts (TAS55, 65, 85)
48
160-180 lbf•ft (217-244 N•m)
Valve housing bolts (TAS40, 55, 65)
1
75-85 lbf•ft (102-115 N•m)
Valve housing bolts (TAS85)
1
108-128 lbf•ft (147-174 N•m)
Item numbers referenced are shown on the exploded
views, pages 13 and 15.
* After tightening to this torque value, the adjuster must
be backed off 1⁄4 to 1⁄2 of a turn as described in step 22
on page 61.
**Torque value indicated is using recommended tools.
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Torque Range Lubricated
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APPENDIX
Special tools can be purchased through:
SPX Corporation
Kent-Moore Tool Group
28635 Mound Road
Warren, MI 48092
1-800-328-6657
steering appendixes
TAS Series Exploded View -- Standard
48
46
49
47
41
TAS85 Construction
45
48
59/60
52/53
49
42
46
41
52A
47
41
40
45
34
23
22
36
36
38
25
23A
37
23
24
26
23A
39
30
29
28
22
27
19
21
31
20
18
17
9
8
16
15
13
15
13A
12
58
11
34
Short "V" Construction
14
32
31
16
10
9
2C
2B
6
12
5
28
54/55
27
20
56
8
7
15
57
4
3
2
1
21
19
Item Description
1
*2
*2B
*2C
*3
*4
5
*6
*7
*8
*9
*10
*11
12
13
13A
14
15
Bolts (4-Valve Housing)
Dirt and Water Seal 13/16" Serr.
Dirt and Water Seal 7/8" Serr.
Dirt and Water Seal 1" Serr.
Retaining Ring
Seal (Input Shaft)
Valve Housing
Seal Ring (Valve Housing)
Seal Ring (Valve Housing)
Seal Ring (2)
O-ring (2)
Seal Ring
O-ring (Valve Housing)
Thrust Washer (Thick)
Input Shaft, Valve, Worm Assy.
Input Sh., Valve, Worm Assy. (Alt.)
Spacer Sleeve (Alt.)
Thrust Bearing (1 or 2)
16
17
*18
19
*20
*21
22
23
24
25
26
27
28
*29
30
*31
*32
34
35
Thrust Washer (Thin)
Bearing Adjuster
Adjuster Locknut
Rack Piston
Teflon Seal Ring
O-ring (Back up; Rack Piston)
Poppet Seat and Sleeve Assy. (2)
Poppet (2)
Poppet Spring
Spacer Rod
Push Tube
Balls
Ball Return Guide Halves (2)
Seal (Cap)
Ball Return Guide Cap
Torx Screws (2-Cap/Strap)
Ball Return Guide Strap
Housing
Grease Fitting
36
37
*38
*39
40
*41
42
43
44
*45
46
47
48
*49
50
51
52
52A
53
54
*55
56
*57
58
59
60
Retaining Ring (2)
Roller Bearing
Dirt Seal
Dirt and Water Seal (Trunnion)
Washer (Spacer)
Seal (2-Output)
Sector Shaft
Adjusting Screw (Sector Shaft)
Retainer (Adjusting Screw)
Gasket (Side Cover)
Side Cover Assembly
Jam Nut
Special Bolts (6 or 8-Side Cover)
Vent Plug (Side Cover)
Bleed Screw (Manual)
Plug (Auto Bleed)
Fixed Stop Screw (Poppet)
Fixed Stop Screw (Poppet-Alt)
Washer (Stop Screw)
Auxiliary Port Plug (2)
O-ring (2-Aux. Port Plug)
Relief Valve Cap
O-ring (Relief Valve)
Relief Valve (2 piece)
Service Poppet Adjusting Screw
Service Sealing Jam Nut
839
*These items are included in complete seal kits along with 406038 lubricant and a service bulletin.
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Service Parts List - Standard
Common Parts
840
Item Description
Part Number
Item Description
1
2
2B
2C
3
4
7
8
9
10
11
12
15
16
17
18
27
29
30
31
32
35
43
44
47
49
50
51
52A
54
55
57
59
60
020251
478044
478060
478050
401637
478076
032823
029123
032200-158
029116
032200-152
400143
070027
400144
400149
027007
213684-X1
478042
400161
020228
400167
037032
021200
062005
025150
036201
213705
021397
021426
415437-A1
032229
032200-153
021407
025119
5
13
13A
14
19
34
42
46
56
58
Bolts (4-Valve Housing)
Dirt and Water Seal 13/16" Serr.
Dirt and Water Seal 7/8" Serr.
Dirt and Water Seal 1" Ser
Retaining Ring
Seal (Input Shaft) (High Temp)
Seal Ring (Valve Housing)
Seal Ring (2)
O-ring (2) (High Temp)
Seal Ring
O-ring (Valve Housing) (High Temp)
Thrust Washer (Thick)
Thrust Bearing (2)
Thrust Washer (Thin)
Bearing Adjuster
Adjuster Locknut
Balls
Seal (Cap)
Ball Return Guide Cap
Torx Screws (2-Cap/Strap)
Ball Return Guide Strap
Grease Fitting
Adjusting Screw (Sector Shaft)
Retainer (Adjusting Screw)
Jam Nut
Vent Plug (Side Cover)
Bleed Screw (Manual)
Plug (Auto Bleed)
Fixed stop screw
Auxiliary Port Plug (2)
O-ring (2-Aux. Port Plug)
O-ring (Relief Valve)
Service Poppet Adjusting Screw
Service Sealing Jam Nut
Valve Housing
Input Shaft, Valve, Worm Assy.
Input Shaft, Valve, Worm Assy. (Alt.)**
Spacer Sleeve (Alt.)**
Rack Piston
Housing
Sector Shaft
Side Cover Assembly
Relief Valve Cap
Relief Valve (2 piece)
*Contact Service/Sales for part numbers
**Applicable to TAS65 gears only
Kits
Items
Description
54 & 55
Port Plug & O-ring
56 & 57
Relief Valve Cap & O-ring
59 & 60
Adj. Screw & Jam Nut
2, 2B, 2C, 3, 4 Input Shaft Seal Kit
TAS40 Seal Kit
TAS55 Seal Kit
TAS65 Seal Kit
TAS85 Seal Kit
Part Number
415437-A1
411061-A1
021407-X1
TAS000001
TAS400003
TAS550004
TAS650012
TAS850003 or 4
Parts Vary by Gear Size
Item Description
TAS40
TAS55
TAS65
TAS85
6
20
21
22
23
23A
24
25
26
28
032829
032828
032827
409118-A2
040210
040248
401662
040209
080154
400158
400159
401674
070030
478052
478053
028527
478051
HFB529000
021277
032829
032830
032831
409118-A2
040210
040248
401662
040209
080154
400160
400165
401650
071032
478041
478045
028519
478040
HFB649000
021434
032616
032590
032615
409118-A2
040210
040248
401662
040209
080154
400156
400157
401650
071033
478041
478045
028519
478040
HFB649000
021434
032834
032547
032556
409118-A6
040217
040249
401684
040218
080158
400162
400163
401685
072004
478057
478059
028534
478084
TAS859000
021434
36
37
38
39
40
41
45
48
L
Parts Vary by Specification*
Seal Ring (Valve Housing)
Teflon Seal Ring
O-ring (Back up; Rack Piston)
Poppet Seat and Sleeve Assy. (2)
Poppet (2-old design)
Poppet (2-new design)
Poppet Spring
Spacer Rod
Push Tube
Ball Return Guide Halves (2) R.H.
L.H.
Retaining Ring (2)
Roller Bearing
Dirt Seal
Dirt and Water Seal (Trunnion)
Washer (Spacer)
Seal (2-Output)
Gasket (Side Cover)
Special Bolts (6 or 8-Side Cover)
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APPENDIX
steering appendixes
TRW Automotive
Steering & Suspension Systems
Service Bulletin #TAS-101
On-Vehicle Poppet Readjustment for TAS
Gears
Revised January, 1993
Electronic Version April, 1998
This TRW Commercial Steering Division service
bulletin has been written to help you repair commercial vehicles more efficiently. This bulletin should
not replace your manuals; you should use them
together. These materials are intended for use by
properly trained, professional mechanics, NOT “Doit-yourselfers”. You should not try to diagnose or
repair steering problems unless you have been
trained, and have the right equipment, tools and
know-how to perform the work correctly and safely.
What are poppets?
Poppets are pressure unloading valves set to trip just before full turn is reached in each direction. When this procedure is completed correctly, system pressure will be reduced before the axle stop screw contacts the axle stop in both
directions.
To determine if the poppets require readjustment or if they are performing properly, install a Power Steering System
Analyzer (PSSA) between the power steering pump and the steering gear. If poppet readjustment is necessary, you
can leave the PSSA in the system to verify that the following procedure is completed properly.
Why might poppets need to be readjusted?
•
•
•
•
•
•
841
Changing to larger tires
Reduced vehicle wheelcut
Pitman arm mistimed, condition corrected
Steering gear being installed on a different truck
Steer axle stop bolt(s) were bent or broken
Steer axle u-bolt(s) were bent or broken
This resetting procedure will work in most cases with at least 13⁄4 hand-wheel-turns from each side
of center. If you're making a large reduction in wheelcut and this procedure does not work, you
may have to internally reset the poppets using the procedure described in the TAS Service Manual.
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Set axle stops,
warm-up system
1.
Set the axle stops to vehicle manufacturer’s
wheelcut or clearance specifications.
Start the engine, and allow the vehicle to idle for 510 minutes to warm the hydraulic fluid. Shut off the
engine.
Assemble
adjusting screw
into nut
2.
If a new poppet adjusting screw and nut are being
used, turn the screw into the non-sealing end of the
jam nut until the drive end of screw is flush with the
nut.
Your steering gear will have either a fixed stop bolt
or an adjusting screw. If the adjusting screw is
already part of the steering gear, back the nut off of
the adjusting screw until it is flush with the end of
the adjusting screw.
Remove poppet
stop bolt
3.
Make sure the engine is off and the road wheels are
in straight ahead position. Remove and discard the
poppet fixed stop bolt (if equipped) and washer (if
equipped) from the lower end of housing.
If the unit has a poppet adjusting screw and sealing
nut that need to be replaced, remove and discard
them.
Turn adjusting
screw assembly
into housing
4.
Turn the adjusting screw and sealing nut assembly,
without rotating the nut on the screw, into the
housing until the nut is firmly against the housing
using a 7⁄32" allen wrench. Tighten the sealing nut
against the housing.
Refill reservoir
5.
Refill system reservoir with approved hydraulic fluid.
842
Do not mix fluid types. Mixing of
transmission fluid, motor oil, or other
hydraulic fluids will cause seals to deteriorate faster.
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steering appendixes
Jack up vehicle
6.
Place a jack under the center of the front axle and
jack up the front end of the vehicle so the steer axle
tires are off the ground.
Push upper poppet
out to prepare it for
setting
7.
a) Start the engine and let it run at idle speed.
b) Note which output shaft timing mark is nearest
the housing piston bore.
c) Turn the steering wheel in the direction that
makes this timing mark move toward the
adjusting screw just installed. Turn in this
direction until axle stop contact is made.
d) Pull hard on the steering wheel (put 30 lbs. rim
pull on a 20" dia. steering wheel) after the axle
stop is contacted.
Set upper poppet
8.
a) Turn the steering wheel in the opposite direction
(end of timing mark away from adjusting screw)
until the other axle stop is contacted.
b) Pull hard on the steering wheel (put 30 lbs. rim
pull on a 20" dia. steering wheel).
c) Release the steering wheel and shut off the
engine.
Back out adjusting
screw
9.
Loosen the sealing nut and back out the adjusting
screw until 1" is past the nut. Tighten the sealing
nut against the housing.
843
Do not hold the steering wheel at full
turn for more than 10 seconds at a
time; the heat build-up at pump relief pressure may
damage components.
Set lower poppet
10.
a) Start the engine and let it idle.
b) Turn the steering wheel in the original direction
(end of timing mark toward adjusting screw), until
axle stop contact is made.
c) Hold the steering wheel in this position (with 30
lbs. rim pull) for 10 seconds, then release.
Repeat this hold and release process as many
times as necessary while completing step 11.
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Position adjusting
screw
11.
a) With steering wheel held at full turn, loosen the
jam nut and hold it in place with a wrench.
b) Turn the adjusting screw in (clockwise) using
finger- pressure only (don't use a ratchet), until
the Allen wrench comes to a stop. Do not
attempt to turn it in farther. Pause the turning-in
process each time the driver releases the
steering wheel; Continue turning only while the
wheel is held at full turn.
c) Back off the adjusting screw 31⁄4 turns and tighten
the sealing nut. Torque the sealing nut to 33-37
lbf•ft.
The procedure is
complete
12.
The poppets have now been completely reset.
Lower the vehicle . Check the reservoir and fill if
required.
The length of the adjusting screw
beyond the nut must be no more than
11⁄16" for proper thread engagement.
The length of adjusting screw
beyond the sealing nut may be
different for each vehicle.
844
TRW Commercial Steering Division
P.O. Box 60
Lafayette, IN 47902
Phone: 765.423.5377
Fax:
765.429.1868
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TRW Automotive
Commercial Steering Systems
Steering Diagnostics
Service Manual
CHART YOUR WAY TO EASY STEERING
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steering appendixes
A warning describes hazards or unsafe practices which could result in
severe personal injury or death.
A caution describes hazards or unsafe practices which could result in
personal injury or product or property damage.
A note gives key information to make following a procedure easier or
quicker.
Notice
This guide was prepared for the purpose of providing general advice concerning the diagnosis and correction of
commercial vehicle steering related problems. This guide is intended for the use of properly trained, professional
mechanics, NOT "Do-it-Yourselfers". Also, this guide should be used in conjunction with service manuals provided by
both the vehicle and component manufacturers. Diagnosis and correction of commercial vehicle steering related
problems should only be handled by properly trained, professional mechanics who have the proper equipment, tools,
instructions and know-how to perform the work properly and safely.
Power Steering System Analyzer (PSSA) Gauge
Some of the tests in this manual require the use of a PSSA. This device is a combination flow meter, shut-off valve,
and pressure gauge. This tool will allow you to measure flow and pressure, and provide a load on the pump through
the hydraulic lines of the steering system. This tool is required to correctly analyze a steering system. TRW recommends that you DO NOT BEGIN TROUBLESHOOTING A STEERING SYSTEM WITHOUT THE USE OF A PSSA. If
you are not sure how to use a PSSA, you may refer to the video available through our website at:
www.trucksteering.com. This video compliments the tests in this book which require the use of the PSSA.
847
Throughout this troubleshooting guide, test procedures are recommended to help locate
the cause of each complaint. While performing these tests, TRW advises that you TAKE
NECESSARY PRECAUTIONS when working with internal vehicle components and hot
hydraulic fluids.
© TRW Inc., 2002
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Table of Contents
Preface ................................................................................ 3
Flow Chart Diagrams .......................................................... 7
Test Procedures ................................................................ 19
Comments ........................................................................ 35
Test Results ...................................................................... 39
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Section 1
Preface
Introduction ......................................................................... 3
Understanding the Complaint
Reading the Flow Charts
Warranty
Definitions ........................................................................ 4-5
Hard Steering
Reduced Wheelcut
Steering Wheel Kick
Binding, Darting, and Oversteer
Directional Pull
Road Wander/Loose Steering
Non-Recovery
Shimmy
Noise
External Leakage
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Introduction
Understanding the Complaint
Steering systems for heavy duty trucks are made up of many components from the steering wheel to the road wheel.
The purpose of the steering system is to give the driver directional control of the vehicle.
When a driver feels the steering control over his/her vehicle is not like it should be, it is up to you to determine if there
is a problem, and if so, figure out what is causing it. It is always easier to fix something if you really understand the
complaint. Some ways you could do this are:
• Talk to the driver and ask a lot of questions like “what, when, where, and how”
• Make sure you can feel or see the problem. Have the driver show you exactly what he/she means.
• Walk around the truck, looking for anything that may be an obvious cause of the problem.
To make your job easier and faster this manual has both the flow charts and test procedures/comments, each in their
own section. Once you have a good understanding of what the complaint is, choose the flow chart that best matches
the symptoms described to you. Because there are different ways to say the same thing, we have provided our
definitions of the 10 most common complaints in this book. Use these to determine which section of the manual
would be helpful to begin diagnosing the steering system.
Reading the flow charts:
Start the chart at the BEGIN box. Follow the lines to the next box answer the question or perform the test to verify
the cause of the complaint, then proceed to the next step. These boxes are arranged in order of likelihood of being
the cause of the driver's complaint. It is important to complete the tests, in order, and follow the flow of the
chart. Locate correct test number in the TEST PROCEDURES section, and follow the test procedure. When you are
done with the test, note the results and correct the root cause. If condition still exists, keep going through the chart (if
necessary, to correct the problem). The results of some tests will need to be recorded. Use the TEST RESULTS
section to record these values.
If you identify a problem through a test procedure it is important that you retest the vehicle to make sure the condition
has been corrected.
Warranty
If you have identified that a steering component on your vehicle needs to be replaced, this does not always mean it is
warrantable. Please read your manufacturer’s warranty carefully before submitting a steering component for warranty
consideration.
853
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Definitions
1. Hard Steering
Hard Steering is when steering effort at the steering wheel is more than 200 inch pounds (typically 18-22 lbs at
the rim of the steering wheel). Steering is still possible, but there is not enough power assist.
Common phrases used:
• Won’t turn
• Locks-up
• Shuts-down
• Turns hard
• Hangs-up
• No assist
• Won’t turn unless moving
2. Reduced Wheelcut
Common phrases used:
• Too great of turning radius required
• Wheelcut restricted
• Not enough turns lock to lock
3. Steering Wheel Kick
Steering Wheel Kick is when the road wheels hit a bump that the steering wheel reacts to. The kick is usually
dampened out quickly.
Common phrases used:
• Kickback
• Backlash
• Bump steer
4. Binding, Darting and Oversteer
Binding is a change or increase in steering wheel effort. Binding will usually not require the effort levels
described in Hard Steering, unless it is severe. Darting and oversteer are words that mean the driver suddenly
gets more turning than he/she wants.
854
5. Directional Pull
Common phrases used:
• Steering pulls to the right (or left)
• Truck pulls to the right (or left)
• A constant force is required to keep the truck going straight
4
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steering appendixes
Definitions
6. Road Wander/Loose Steering
Common phrases used:
• Lash in steering
• Lost motion in steering
• Continual corrections are needed at the steering wheel to keep the vehicle from wandering
7. Non-Recovery
Common phrases used:
• Wheels don’t return to straight ahead
8. Shimmy
A severe Shimmy condition can be felt at the steering wheel. Typically once something triggers a Shimmy
condition to occur it is sustained until the driver does something (such as slow down) to dampen out the
condition.
Common phrases used:
• Shake at steering wheel
9. Noise
Common phrases used:
• Steering is noisy
• Clicking or clunking sound is heard when steering
10. External Leakage
Common phrases used:
• Loss of steering fluid
• Continual adding of fluid in reservoir required
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Section 2
Flow Chart Diagrams
Hard Steering ...................................................................... 8
Reduced Wheelcut ............................................................. 9
Steering Wheel Kick ......................................................... 10
Binding, Darting, and Oversteer ....................................... 11
Directional Pull .................................................................. 12
Road Wander/Loose Steering ........................................... 13
Non-Recovery ................................................................... 14
Shimmy ............................................................................. 15
Noise ................................................................................. 16
External Leakage .............................................................. 17
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Hard Steering
Begin
Preliminary Checklist
1. Power steering fluid in reservoir
2. Tire pressure values
(TEST #1)
3. Fifth wheel properly greased (TEST #2)
4. Vehicle has not been overloaded
Occurs in only
one direction?
Yes
Air in System
TEST #9
Internal Leak
TEST #7
Done
No
Intermittent
loss of power
assist?
Yes
Yes
Is I-Shaft
Binding ?
Intermittent Mechanical
TEST #19
Replace I-Shaft
Verify problem has
been corrected
Done
No
Intermittent Hydraulic
COMMENT K
Does oil in
reservoir
smell hot
or burnt?
Yes
Restricted Line
TEST #10
Yes
Restriction
found?
Inspect suspect component
for blockage, damage, or
improper hoses and fittings
No
No
Call technical
service
Pump Steering Pump
TEST #5.1
No
Replace Component or Hose
Verify problem has
been corrected
Flow Control Response
TEST #6.1
Are any numbers
input on chart, below
specifications?
Yes
Replace Pump
Verify problem has
been corrected
Internal Leak
TEST #7
Fixed?
Yes
Done
No
No
Cold start
only?
Yes
Replace Steering Gear
Verify problem has
been corrected
Call technical
service
Restricted Line
TEST #10
Pump Vanes (Reprime)
COMMENT A
No
Check for these Conditions
1. Binding at input side of gear
a. U-joint rubbing - TEST #17
b. Intermediate shaft binding - TEST #19
2. Firewall boot interference/cab mount drop - TEST #18
3. Gear to frame interfernce - TEST #4
4. Binding at king pins/steer axle linkage - TEST #3
Power Steering Pump
TEST #5
858
Are any numbers
input on chart, below
specifications?
Yes
Replace Pump
Verify problem has
been corrected
Done
No
Steering too Fast
COMMENT B
Chart
TRW Steering Gear
Flow Requirements
Restricted Line
TEST #10
Fixed?
No
Yes
Air in System
TEST #9
COMMENT H
Fixed?
Yes
Done
No
Check if correct
pump has been
installed for your
application and
consult your OEM
truck representative.
END
HARD STEERING
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Internal Leak
TEST #7
steering appendixes
Reduced Wheelcut
Begin
Set Axle Stops to OEM Specifications
TEST #11
Fixed?
Yes
Done
No
Pitman Arm / Output Shaft
TEST #12
Timing Mark Diagram
Figure 12.1
Fixed?
Yes
Done
No
Are poppets
set correctly
on gear?
Misadjusted Draglink
TEST #13
Draglink Diagram
Figure 13.1
No
Poppet Setting
TEST # 14
END
REDUCED WHEELCUT
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Steering Wheel Kick
Begin
Air in System
TEST #9
COMMENT H
Done
Looseness in Mechanical System
TEST #15
TEST #16
Verify if looseness in the
system has been eliminated
Fixed?
Yes
Done
No
Gear Adjustment Procedures
HFB (Valve)
TAS/HFB/HF (Sector Shaft)
Shock Absorbers
Worn or missing shocks
Reference TMC document
RP643, Section 1. "Shock
Absorbers"
Linkage Geometry
COMMENT C
Power Steering Pump
TEST #5
Flow Control Response
TEST #6
Are any numbers
input on chart, below
specifications?
Yes
No
Done
END STEERING
WHEEL KICK
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steering appendixes
Binding, Darting, and Oversteer
Begin
Cyclic binding
at steering
wheel?
Yes
Occuring
once per
revolution?
Yes
Yes
Column Friction, Eccentric
Condition, Interference
TEST #18
Fixed?
U-joint Lube or
Improperly Phased
TEST #17
TEST #19
Fixed?
Done
No
More than
one U-joint?
No
Yes
Done
Excessive U-joint Angle
COMMENT D
Check for these Conditions
1. Binding at input side of gear
a. U-joint rubbing - TEST #17
b. Intermediate shaft binding - TEST #19
2. Firewall boot interference/cab mount drop - TEST #18
3. Gear to frame interfernce - TEST #4
4. Binding at king pins/steer axle linkage - TEST #3
Fixed?
Yes
Done
No
Vehicle Alignment
TEST #21
Fixed?
Yes
Done
No
Steer Axle Wheel
Bearing Adjustment
TEST #22
Fixed?
Yes
Done
No
Check
Caster and toe on the
front axle
Fixed?
Yes
861
Done
No
Power Steering Pump
TEST #5
COMMENT I
Fixed?
Yes
Done
No
Flow Control Response
TEST #6
Pump Reference Chart
Flow settings according to
pump part numbers
END BINDING, DARTING,
& OVERSTEER
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Directional Pull
Begin
Does
vehicle pull
while braking
or accelerating?
Yes
Braking
No
Unequal Braking Force
TEST #25
Accelerating
COMMENT F
Preliminary checklist
1. Vehicle pre-alignment TEST #21
2. Wheel bearing adjustment TEST #22
3. Air suspension adjustment TEST #23
4. Steer tires
a. Swap tires
b. Belt tread mismatched
5. Vehicle loading (Overloaded)
Unbalanced Gear
TEST #24
Power Steering Pump
TEST #5
Fixed?
No
Call technical
service
Done
END
DIRECTONAL PULL
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Fixed?
Yes
Yes
862
No
steering appendixes
Road Wander/Loose Steering
Begin
Wheel Bearing Adjustment
TEST #22
Torque Steer
COMMENT E
Preliminary checklist
1. Vehicle pre-alignment (TEST #21)
2. Steer tires
(TEST #1)
a. Swap tires
b. Belt tread mismatched
3. Fifth wheel properly greased (TEST #2)
Fixed?
Yes
Done
No
Torque steering gear
mounting bolts to OEM
specifications
Fixed?
Yes
Done
No
Mechanical Looseness
TEST #15
TEST #16
TEST #20
Fixed?
Yes
Done
No
Rear Steer Condition
COMMENT G
Fixed?
Yes
Done
No
Call technical
service
863
END
ROAD WANDER
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Non-Recovery
Begin
Preliminary Checklist
1. Tire pressure values (Entire vehicle) TEST #1
2. Fifth wheel properly greased TEST #2
3. Vehicle pre-alignment TEST #21
4. Verify caster angle
Binding in Steer Axle Linkage
or King Pins
TEST #3
Gear/Column Binding
TEST #8
Binding
isolated to
gear or
column?
Yes
Steering Gear
No
Gear to Frame Interference
TEST #4
Column
Steering too Tight
TEST #16
Column Checks
TEST #18
Driveline / Slip Joint Travel
and U-joint Seizure
TEST #17
TEST #19
Power Steering Pump
TEST #5
COMMENT I
Miter Box
TEST #20
Restricted Line
TEST #10
Firewall Boot Interference
Fixed?
No
Call technical
service
Done
END
NON-RECOVERY
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Fixed?
Yes
Yes
864
No
steering appendixes
Shimmy
Begin
Mechanical Looseness
TEST #15
TEST #22
Fixed?
Yes
Done
(TEST #1)
No
Tire Wheel Balance
and Runout
COMMENT G
Fixed?
Yes
Done
No
Air in System
TEST #9
COMMENT H
Fixed?
Yes
Done
No
Call technical
service
END
SHIMMY
865
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Noise
Begin
Occurs
only when
steering?
Rubbing or
squeaking
sound?
Yes
No
Yes
No
Is steering
wheel touching
the column?
Lubricate Horn Contact
TEST #27
Check if wheel moves
side to side relative to
column. (See NOTE)
Yes
Less than .25 in. (6.35 mm) at 18 in. (547 mm)
at steering wheel rim is normal.
Correct the source
of the problem.
No
2
NOTE
Yes
Is a rattle
sound present?
Check I-Shaft
TEST #29
No
Yes
Is noise
associated with
the steering
column?
Yes
Call technical
service
Yes
Fixed?
Check for loose steering wheel
and/or column mounting. Tighten
if necessary.
Occurs only
when vehicle
is stationary?
Done
No
Call technical
service
Hood
No
Is noise due
to pump relief
valve/belt
squeal?
No
No
Occurs
when vehicle
is moving?
No
Is the related
noise originating
from under hood or
within the cab?
Yes
No
Cab
Yes
Some noises are normal.
Inspect to make sure a more
serious condition does not
exist.
Go to
1
Go to
2
1
Call technical
service
Restricted Line
TEST #10
Lash in System
TEST #15
Torque steering gear
mounting bolts to OEM
specifications
Fixed?
Yes
No
Call technical
service
Yes
Fixed?
Done
No
Low fluid level or
loose inlet line
Yes
Fixed?
866
Done
No
Plugged reservoir
vent or debris in
reservoir
Clean and Flush
Steering System
COMMENT J
Yes
Fixed?
Done
No
Improperly installed
filter in reservoir
Yes
Fixed?
No
Call technical
service
END
NOISE
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Done
Done
No
Location of Shaft in Column
TEST #28
Is noise
mechanical
in nature?
Yes
Fixed?
Yes
Check if shaft is moving
in the bearing.
Done
steering appendixes
External Leakage
Begin
Yes
Occurs in only
one direction?
Correct the problem causing
the leak and verify it has been
fixed.
No
Fittings
Check the following
1.
2.
3.
4.
5.
6.
Hoses
Loose
Defective
(TEST #1)
Overtightened
Damaged sealing surface
Mismatched fitting/Hose connection
O-ring fitting hardened
Check the following
1.
2.
3.
4.
5.
6.
Clamps loose
Heat or age cracked
(TEST #1)
Twisting or abrasion (wear)
Misassembled end
Loose fitting connection
Wet or signs of weeping (Test 5.1)
Pump / Reservoir /
Cooler
Check the following
Steering Gear
Check the following
1.
2.
3.
4.
5.
6.
1.
2.
3.
4.
5.
Broken or cracked brackets, filler tops, connector dipstick
Plugged vent hole in filler cap
Improper oil level in reservoir
Foaming due to filter element being improperly installed
Drive shaft seal
Cooler
Poppet screw or sealing nut loose
Input/Output shaft seals (TEST #1)
Valve housing sealing areas
Side cover seal vent plug, bolts, side cover gasket
Porosity in housing side cover or valve housing
867
END
EXTERNAL LEAKAGE
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Section 3
Test Procedures
Test #1 - #3 ....................................................................... 20
Test #4 .............................................................................. 21
Test #5 .............................................................................. 22
Test #5.1 ........................................................................... 23
Test #6 .............................................................................. 24
Test #6.1 ........................................................................... 25
Test #7 .............................................................................. 26
Test #8 - #9 ....................................................................... 27
Test #10 ............................................................................ 28
Test #11 - #14 ................................................................... 29
Test #15 - #16 ................................................................... 30
869
Test #17 - #19 ................................................................... 31
Test #20 - #25 ................................................................... 32
Test #26 - #29 ................................................................... 33
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Test #1
Steer Tire Check
1. Look for: Tire damage, Uneven or extreme tread wear, mismatched tires or other wear indicators that would cause the
problem. Figure 1.1.
2. Check tire pressures on steer axle tires. Figure 1.2.
Test #2
Fifth Wheel and Trailer Plate
Figure 1.1
Figure 1.2
Figure 2.1
Figure 2.2
1. Look for dry fifth-wheel or trailer plate. Figure 2.1.
2. Look for damage to fifth-wheel or trailer plate. Figure 2.2.
3. Inspect fifth-wheel for looseness.
Test #3
Steer Axle and Linkage Binding
1. With vehicle steer tires on radius plates (turntables) or equivalent,
disconnect the drag link or pitman arm from the steering gear,
(and linkage from assist cylinder if there is one on the vehicle).
Figure 3.1.
Do not steer the gear with linkage removed, as
misadjustment of automatic poppets may result.
2. By hand, pull the tire to one axle stop and release (engine off).
The tire should self-return to near straight ahead. Figure 3.2.
3. Repeat the test in the opposite direction.
4. If tire does not self-return to near straight ahead, a problem is
likely in steer axle king pin bushings/bearings or linkage.
Figure 3.1
870
Figure 3.2
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Test #4
Steering Gear Mounting
1. Look for anything between the steering gear and frame that could
cause a binding problem. For example: hoses or brackets that
have been routed, or are interfering between the steering gear
and frame, frame flanges or spring mounting points. Figure 4.1.
Mounting pads lower than steering gear housing, lack of clearance
between frame and steering gear valve housing adapter, sector
shaft adjusting screw and nut contact with access adjustment
hole in frame. If interference is found, correct the problem.
Figure 4.1
2. If the steering gear has been mounted to the frame in a way that
causes the gear to distort (not be flat), it may cause a steering
problem. Figure 4.2. Checking to see if distortion is present on
the vehicle may require the following test:
3. With vehicle parked and engine running, steer the wheel slowly
checking for a binding-type of feel at the steering wheel. When
binding is felt (stop engine loosen one mounting bolt restart
engine) and steer the vehicle again. Continue to loosen one
mounting bolt at a time, shutting off engine each time, and check
for improvement in the binding condition. If improvement is made
by loosening the bolts, determine by inspection the condition
causing the gear to distort and correct the problem. Distortion of
.030" (.80 mm) or less is acceptable. If greater than .030" (.80
mm) surface flatness, condition must be corrected.
Figure 4.2
871
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Test #5
Power Steering Pump Test
IMPORTANT: Read the following instructions below before
completing Table 5, located in the "TEST RESULTS" section.
Verify Engine Idle speed per your OEM specifications.
1. Install temperature gauge in reservoir. Figure 5.1. Install PSSA in
pressure line with shut-off valve fully open. Figure 5.2.
2. Run the engine at 1000 rpm.
Figure 5.1
When closing the PSSA shut off valve, do so
slowly and keep an eye on the pressure gauge. Do
not allow the system to exceed 3000 psi (207 bar)
for safety of personnel and to prevent damage to
the vehicle.
Do not keep the load valve closed for more than 5
seconds at a time because damage to the system
may result from excessive heat build- up.
3. Measure and record the following flow and pressure readings (see
chart) by adjusting the load valve while listening for any unusual
noises as the valve is being opened and closed. Figures 5.3-5.7.
Figure 5.2
4. Now with the load valve fully open, increase the engine speed to
governed RPM and measure and record the following flow and
pressure readings by adjusting the load valve while listening for
any unusual noises as the valve is being opened and closed.
5. Determine the recommended flow range and maximum allowable
system pressure for the steering system being used by referring
to your service manual.
Figure 5.3
6. Compare the minimum and maximum flows (and the relief
pressure you measured) to gear and pump specifications.
872
7. If the minimum measured pump flow is less than the minimum
recommended flow for the steering gear used (see Steering
Gear Flow Requirements chart), the pump may not be putting
out enough flow for an adequate steering speed. If the maximum
system pressure is lower than that specified for the pump (check
your manual), it may not be developing enough pressure to steer.
If either case exists, the pump needs to be repaired or replaced.
When hydraulic tests are completed and fluid lines are
reconnected, check fluid level and bleed the air from
the hydraulic system.
Figure 5.5
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steering appendixes
Test #5.1
40 Minute Power Steering Pump Test
IMPORTANT: Read the following instructions below before
completing Table 5.1 in the "Test Results" section.
Verify Engine Idle speed per your OEM specifications
1. Install temperature gauge in reservoir. Figure 5.1. Install PSSA in
pressure line with shut-off valve fully open. Figure 5.2. Park the
vehicle outside. Record ambient temperature. Run the engine at
governed RPM for 40 minutes to bring the fluid up to an elevated
testing temperature. Measure and record the fluid temperature at
the start and at 10, 20, 30 and 40 minutes. Do not allow the
temperature to exceed 250° F (121° C).
If the temperature goes over 250° F (121° C) , or
150° F (66° C) above the surrounding temperature
(ambient) at any time during the test, stop the test.
This temperature level is considered extreme and
steering system performance and life will be seriously
affected. Damage to hoses, seals, and other components may result if operated at extreme temperature.
If the steering system is operating above the recommended temperatures, the heat problem may be the
root cause of the complaint.
Figure 5.6
Figure 5.7
2. Run the engine at idle speed.
When closing the PSSA shut off valve, do so
slowly and keep an eye on the pressure gage. Do
not allow the system to exceed 3000 psi (207 BAR)
for safety of personnel and to prevent damage to
the vehicle.
Do not keep the load valve closed for more than 5
seconds at a time because damage to the system
may result from excessive heat build-up.
873
3. Measure and record the following flow and pressure readings (see
chart) by adjusting the load valve while listening for any unusual
noises as the valve is being opened and closed. Figures 5.3-5.7.
4. Now with the load valve fully open, increase the engine speed to
governed RPM and measure and record the following flow and
pressure readings by adjusting the load valve while listening for
any unusual noises as the valve is being opened and closed.
5. Determine the recommended flow range and maximum allowable
system pressure for the steering system being used by referring
to your service manual.
6. Compare the minimum and maximum flows, and the relief
pressure you measured to gear and pump specifications.
7. If the minimum measured pump flow is less than the minimum
recommended flow for the steering gear used (see Steering
Gear Flow Requirements chart), the pump may not be putting
out enough flow for an adequate steering speed. If the maximum
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system pressure is lower than that specified for the pump (refer
to your OEM service manual), it may not be developing enough
pressure to steer. If either case exists, the pump needs to be
repaired or replaced.
When hydraulic tests are completed and fluid lines are
reconnected, check fluid level and bleed the air from
the hydraulic system.
Test #6
Pump Flow Control Response
Figure 6.1
IMPORTANT: Read the following instructions below before
completing Table 6, in the "Test Results' section
1. Install temperature gauge in reservoir. Figure 6.1. Install PSSA in
pressure line with shut-off valve fully open. Figure 6.2.
If the temperature goes over 250° F (121° C) , or
150° F (66° C) above the surrounding temperature
(ambient) at any time during the test, stop the test.
This temperature level is considered extreme and
steering system performance and life will be seriously
affected. Damage to hoses, seals, and other components may result if operated at extreme temperature.
If the steering system is operating above the recommended temperatures, the heat problem may be the
root cause of the complaint.
Do not keep the load valve closed for more than 5
seconds at a time because damage to the system
may result from excessive heat build-up. (Do not
allow the pressure to exceed 3000 psi (207 bar).
2. With the engine at idle, note the flow rate. Fully close the load
valve until the flow drops to zero. Quickly open the load valve
observing the flow meter. The flow rate must instantly return to
the reading you noted above.
874
3. With the load valve open run the engine to governed speed and
note the flow rate. Fully close the load valve until the flow drops
to zero. Quickly open the load valve observing the flow meter. The
flow rate must instantly return to the reading noted above.
4. Conduct this pump response test three times at idle and three
times at 1500 RPM. If the flow rate does not return immediately,
the pump is malfunctioning, which can result in momentary loss
of power assist.
When hydraulic tests are completed and fluid lines are
reconnected, check fluid level and bleed the air from
the hydraulic system.
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Figure 6.2
steering appendixes
Test #6.1
40 Minute Pump Flow Control Response
Read the following instructions below before completing
Table 6.1 in the "Test Results' section
1. Install temperature gauge in reservoir. Figure 6.1. Install PSSA in
pressure line with shut-off valve fully open. Figure 6.2. Park the
vehicle outside. Record ambient temperature. Run the engine at
governed RPM for 40 minutes to bring the fluid up to an elevated
testing temperature. Measure and record the fluid temperature at
the start and at 10, 20, 30, and 40 minutes. Do not allow the
temperature to exceed 250° (121°C)
If the temperature goes over 250° F (121° C) , or
150° F (66° C) above the surrounding temperature
(ambient) at any time during the test, stop the test.
This temperature level is considered extreme and
steering system performance and life will be seriously
affected. Damage to hoses, seals, and other components may result if operated at extreme temperature.
If the steering system is operating above the recommended temperatures, the heat problem may be the
root cause of the complaint.
Figure 6.1
Figure 6.2
Do not keep the load valve closed for more than 5
seconds at a time because damage to the system
may result from excessive heat build-up. (Do not
allow the pressure to exceed 3000 psi (207 bar).
2. With the engine at idle, note the flow rate. Fully close the load
valve until the flow drops to zero. Quickly open the load valve
observing the flow meter. The flow rate must instantly return to
the reading you noted above.
3. With the load valve open run the engine to governed speed and
note the flow rate. Fully close the load valve until the flow drops
to zero. Quickly open the load valve observing the flow meter. The
flow rate must instantly return to the reading noted above.
875
4. Conduct this pump response test three times at idle and three
times at 1500 RPM. If the flow rate does not return immediately,
the pump is malfunctioning, which can result in momentary loss
of power assist
When hydraulic tests are completed and fluid lines are
reconnected, check fluid level and bleed the air from
the hydraulic system.
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Test #7
Measured Internal Leakage
1. Install temperature gauge in reservoir. Figure 7.1. Install PSSA in
pressure line with shut-off valve fully open. Figure 7.2.
THIS TEST CAN BE DANGEROUS IF NOT PERFORMED CORRECTLY. KEEP YOUR FINGERS
CLEAR OF THE AXLE STOPS AND SPACER BLOCK
DURING THIS TEST. MAKE SURE THAT THE
SPACER BLOCK CONTACTS THE AXLE STOP
SQUARELY. CONTACT THAT IS NOT SQUARE
COULD BREAK THE AXLE STOPS OR DANGEROUSLY THROW OR EJECT THE SPACER BLOCK.
2. To test the steering gear for internal leakage, you must first
prevent operation of the gear’s internal unloading (poppet) valves
or relief valve (or both, in some gears). This will allow full pump
relief pressure to develop. To prevent operation of the poppets,
place an unhardened steel spacer block, about one inch thick and
long enough to keep your fingers clear between the axle stop at
one wheel. Figures 7.3-7.4. To prevent operation of the relief
valve, remove the relief valve cap, o-ring and two piece relief
valve, if equipped, from valve housing. Install the relief valve plug,
special tool number J37130 in its place.
Figure 7.1
Figure 7.2
Be sure you reinstall the relief valve and valve cap
with new o-ring, back onto the gear after leakage test.
When running this test, do not hold the steering
wheel in the full turn position for longer than 5 to
10 seconds at a time to avoid damaging the pump.
876
KEEP YOUR FINGERS CLEAR OF THE AXLE STOPS
AND SPACER BLOCK DURING THIS TEST. MAKE
SURE THAT THE SPACER BLOCK CONTACTS THE
AXLE STOP SQUARELY. CONTACT THAT IS NOT
SQUARE COULD BREAK THE AXLE STOPS OR
DANGEROUSLY THROW OR EJECT THE SPACER
BLOCK.
Figure 7.3
3. With the fluid temperature between 125-135° F (52-57° C), turn
the steering wheel until the axle stop bolt contacts the spacer
block.
4. Apply 20 pounds of force to the rim of the steering wheel during
this test to be sure that the steering gear control valve is fully
closed. Figure 7.5. The pressure gauge should now read pump
relief pressure, as noted during the Flow Control Response Test
(Test #6). You can now read steering gear internal leakage on the
flow meter.
Figure 7.4
5. Repeat this test for the opposite direction of turn.
6. If internal leakage is greater than 1 gpm (3.8 lpm) and there is no
auxiliary hydraulic linear or rotary cylinder in the system, repair or
replace the gear. If the internal leakage is greater than 2 gpm (7.6
lpm), and there is an auxiliary hydraulic linear or rotary cylinder in
the system, controlled by the gear, isolate the auxiliary cylinder
from the system by disconnecting the auxiliary cylinder hydraulic
Figure 7.5
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steering appendixes
lines at the gear auxiliary ports. Plug the steering gear ports with
suitable steel or high pressure plugs or caps.
In the event that a rotary cylinder is used in the system, connect
the disconnected lines together with a suitable union fitting. In
the case of a linear cylinder, first plug the disconnected lines and
then disconnect the cylinder from the steering linkage, making
sure it will clear the steered axle. Figures 7.6-7.7.
Repeat the internal leakage test. If the internal leakage is less than
1 gpm (3.8 lpm), repair or replace the auxiliary cylinder. If the
internal leakage is greater than 1 gpm (3.8 lpm), repair or replace
the gear.
Figure 7.6
When hydraulic tests are completed and fluid lines are
reconnected, check fluid level and bleed the air from
the hydraulic system.
Test #8
Steering Column Binding
1. With the vehicle parked, the engine off, and the steer axle jackedup, slowly steer the vehicle until the binding position is located.
Figure 7.7
2. With the steering gear at this position, remove the steering
column assembly from the steering gear. Note the correct
position of the column and steering gear for reassembly after test.
Figure 8.1
3. Rotate the steering gear input shaft no more than 1/4 turn each
direction and check if binding is still present. Figure 8.2 If binding
is not felt, correct the steering column problem.
Test #9
Air in Hydraulic System
Figure 8.1
1. Inspect reservoir for foaming or air bubbles. Figure 9.1 If foaming
or bubbles are seen, air is being sucked into the system through
cracks or loose fittings. Look for oil level changes engine off
versus engine on, if fluid level increases when the vehicle is shut
off, there is an air pocket trapped in the steering gear. The
increase may not be noticeable, depending on the size of the
pocket.
2. Bleed the steering gear (if there is a manual bleed screw at the
top of the gear). With system at normal operating temperature
and engine at proper idle speed and running, open the bleed
screw and wait until clean, clear oil begins to flow from the gear.
Close the bleed screw and steer the vehicle completely from stop
to stop.
877
Figure 8.2
3. Repeat the bleeding operation three times, and recheck oil level in
reservoir to make sure there is enough oil for the system to
operate properly.
Figure 9.1
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Test #10
Restricted Hydraulic Line
Read the following instructions below before completing
Table 10, in the "Test Results' section
1. Look at the supply line that goes to the pump to check for kinking
or any other obstructions or irregularities on the inside of the
hose. Figure 10.1.
2. Install PSSA with load valve fully open. Figures 10.2-10.3. Insert
temperature gauge into reservoir. With oil between 125-135 °F
(52-57 °C), determine a test engine speed (RPM) that causes
pump to deliver 3, 4, 5 or 6 gpm (11, 15, 19, or 23 lpm) (whichever is easier) and note this speed.
Figure 10.1
3. Remove the PSSA and install a low pressure gauge (200-300 psi
(14-21 bar)) maximum with approximately 10 psi (.70 bar) per
division) in the pressure line to the steering gear at the pump end.
Install a temperature gauge in the power steering reservoir.
Do not allow system pressure to exceed the rating
of the gauge during the following procedure or
damage to the gauge will result. Extremely high
restrictions may be indicated with the PSSA gauge
as installed with load valve fully open.
Figure 10.2
Be sure that the steering gear input shaft is not being
restrained from recentering because this will cause a
false steering gear pressure drop. If there is any
question, conduct this test with the steering column
removed.
4. Bring the power steering fluid temperature to 125-135 °F (52-57
°C), at engine idle, with no steering force applied to the steering
wheel. Figure 10.4.
878
Figure 10.3
5. At the test engine speed selected from step 2 above, measure
and record the gauge reading and shut off the engine. This
measures total system pressure.
6. Remove the pressure and return lines from the steering gear and
connect them together with a fitting that will not restrict the flow.
Figure 10.5.
7. Start the engine, and run at the RPM identified in step 2 with the
fluid temperature between 125-135 °F (52-57 °C).
8. Measure and record gauge reading and shut off engine. This is
hydraulic line/reservoir pressure.
Figure 10.4
9. The difference between the total system pressure gauge reading
and the hydraulic line/reservoir pressure gauge reading is the
steering gear pressure drop. For a TRW steering gear, at a flow of
3, 4, 5 or 6 gpm (11, 15, 19, or 23 lpm), the drop should not be
greater than 30, 40, 55 or 70 psi (2.0, 2.8, 3.8, 4.8 bar) respectively. The line/reservoir pressure drop for a flow of 3, 4, 5 or 6
gpm (11, 15, 19, or 23 lpm) should not be greater than 20, 20, 25
or 25 psi (1.4, 1.4, 1.7, 1.7 bar) respectively.
Figure 10.5
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Test #11
Axle Stop Setting
Put vehicle steer tires on radius plates (turntables). Check to
make sure axle stops are set to manufacturer’s specifications.
Figure 11.1.
Test #12
Pitman Arm and Output Shaft Alignment
Look to make sure the output shaft timing mark is lined up with
the pitman arm timing mark. Some pitman arms have more than
one mark, so make sure the right one is used. Figure 12.1.
Figure 11.1
Test #13
Misadjusted Drag Link
The length of the drag link must be correct for the steering
system. Check the length after you make sure the pitman arm/
shaft timing marks are aligned, the gear is at its center position,
and the road wheels are straight ahead. Figure 13.1.
Figure 12.1
Test #14
Poppet Setting Procedure
1. If you are working on a newly-installed TAS steering gear, refer to
the service manual to correctly set the poppets. If you are
working on a steering gear, other than a TAS series, refer to the
OEM’s service manual for correct poppet setting instructions.
2. To set poppets on a TAS series gear using the adjustable service
kit, refer to your steering gear service manual.
Figure 13.1
879
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Test #15
Lash in Steering System
Two people are needed for this test. One person will slowly turn
the steering wheel back and forth one-quarter turn each way from
center with the engine idling. The other person should check for
looseness at each of the following areas from steering wheel to
road wheels: Figures 15.1-15.5.
* Steering wheel to steering column
* U-joints, or slip-joint and/or miter boxes
* Steering column to steering gear input shaft
* Steering gear input shaft to steering gear output shaft
* Pitman arm to output shaft
* Drag link to pitman arm connection
* Drag link ends (sockets) and adjustable areas
* Axle arm to drag link connection
* King pin axle connections (bushings)
* Tie rod arms to tie rod connection
* Tie rod ends (sockets) and adjustable areas
* Steering spindle
* Wheel bearings
* Lug nuts
* Spring pin connectors
* Front axle u-bolts
* Spring hanger brackets/rear shackles
Figure 15.1
Figure 15.2
Cracked or broken components can cause symptoms
similar to loose components but may be more difficult
to find.
Be sure to check rear drive axles for any looseness
and inspect tires for signs of abnormal wear.
Test #16
Steering Gear Adjustment
Figure 15.3
Check and adjust according to the appropriate service manual for
your steering gear if necessary
880
Figure 15.4
Figure 15.5
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Test #17
U-Joint Phasing and Lubrication
1. Make sure u-joints are properly lubricated.
2. Steering column assemblies with more than one universal joint
(cardan type) can cause a cyclic binding feel or torque variation at
the steering wheel if the u-joints are not in phase with each other.
Figure 17.1-17.2. If a steering column assembly with multiple ujoints is taken apart, it must be reinstalled with the timing marks
for slip mechanisms aligned. This is true for both the cross-type
and the splined-type two-piece intermediate shaft.
Figure 17.1
Test #18
Steering Column Interference
Position steering wheel at the location where steering wheel
interference is noticed, and look for something interfering or
rubbing on the rotating column assembly such as brackets, bolts,
floorboard, boot, etc.
Test #19
Intermediate Column Interference
Figure 17.2
1. Check the slip column by looking to make sure there is proper
travel allowance when in use. Figure 19.1.
2. Look for wear or galling. Figure 19.2.
3. Check slip column for too much slip force
Figure 19.1
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Figure 19.2
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Test #20
Miter Box Misadjusted (if equipped)
Check and adjust per manufacturer’s instructions. Figure 20.1.
Test #21
Vehicle Alignment
Check alignment of steered axle and rear drive axles, and trailer
axles (if problem only exists with trailer). Figure 21.1.
Figure 20.1
Test #22
Wheel Bearing Adjustment
Verify that adjustment is made according to manufacturer’s
specification. Figure 22.1.
Test #23
Air Suspension Adjustment
Check and set to manufacturer’s specifications
Figure 21.1
Test #24
Gear Imbalance
1. Install a low pressure gauge (200-300 psi (14-21 bar) maximum
with approximately 10 psi (.70 bar) per division) in the pressure
line from pump to gear. Figure 24.1.
Do not allow system pressure to exceed the rating
of the gauge in the following procedure or
damage to the gauge will result.
Figure 22.1
2. At engine idle, slightly turn the steering wheel one direction until a
pressure rise is observed at the gauge. Figure 24.2.
882
3. Stop steering and gently allow the steering wheel to recenter.
4. Next slightly turn the steering wheel the opposite direction while
observing the gauge and determine if pressure initially rises or
falls with initiation of a turn.
5. Repeat test a few times in each direction.
6. If a consistent fall in pressure is associated with the initiation of a
turn in one direction, the steering gear’s control valve is unbalanced and needs to be replaced.
Figure 24.1
Test #25
Unequal Brake Force
Visually inspect brake assemblies for oil/grease on braking surfaces, and overall condition of brake surfaces. Adjust or replace
brakes if necessary.
Figure 24.2
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Test #26
Tire Balance / Runout
Have wheel assemblies balanced and checked for lateral and
radial run out per manufacturer’s specifications. Preferred method
for checking balance is with wheels still on the vehicle. Balance
includes total rotating assembly.
TEST #27
Steering Column Noise
If column does not include a clockspring, remove steering wheel
and add dielectric grease to the horn contact. The grease TRW
uses is Model No. K-5/X Semifluid CA, product code 134613, from
Century Lubricants. If noise continues, check steering wheel and
shroud (not applicable to columns with clockspring).
TEST #28
Steering Column Bearing
Check upper bearing gaskets. Gaskets should cover bearing.
TEST #29
Intermediate Column Lash
Check intermediate column (I-Shaft) for torsional lash in U-Joints
of slip section. Replace intermediate column if necessary.
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Section 4
Comments
Comment A - H ................................................................. 36
Comment I - K ................................................................... 37
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Comment A
Some power steering pumps have a temporary state during which the pumping element vanes do not extend. Usually
increasing engine speed briefly will correct the problem.
Comment B
The maximum speed of steer with power assist for a power steering gear is limited by the pump flow and internal
leakage. Example: Recommended minimum flow for a new TAS65 steering gear is 3.0 gpm (11.4 lpm), and is based
on a maximum steering speed capability of 1.5 steering wheel turns per second.
Comment C
Vehicle linkages are designed to minimize the affect at the steering gear and steering wheel during normal steered
axle/suspension movements. Be sure that linkage used is as specified by vehicle manufacturer.
Comment D
A single u-joint operating at an angle will cause a cyclic torque variation at the steering wheel. The amount of torque
variation increases with the amount of operating angle. A secondary couple that side loads the input shaft also increases with increased u-joint angles. U-joint operating angles of 15 degrees or less will minimize the torque variation
felt at the steering wheel.
Comment E
Deflections in the suspension and linkage, front and rear, due to high engine generated torque levels can cause a
steering effect. This most often occurs at lower vehicle speeds while accelerating.
Comment F
The location of the axle arm ball center is important during spring wind-up conditions such as severe braking. A
steering arm different from that specified by the manufacturer could cause a steering effect while braking.
Comment G
Soft or loosely supported rear suspensions may allow the rear driving axles to become non-square with the centerline
of the chassis during load shifting or trailer roll which will tend to produce a steering effect.
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Comment H
Power steering pump cavitation
Pump cavitation is defined as a “wining” or noisy power steering pump. Usually, pump cavitation is most noticed
during engine start-up at low temperature extremes. However, other conditions can cause the power steering pump
to continually cavitate and cause internal pump damage, and ultimately, failure. These conditions are:
1. Twisted, loose, or cracked inlet line
2. Inlet line blockage due to:
a. Contamination - dirt and foreign material
b. Damaged filters
c. Reservoir components
d. Inner hose liner separation
3. Displaced (improper or improperly installed) filters
4. Reservoir cap “vent” plugged
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Comment I
Excessive Flow
TRW steering gears are rated for 8 gpm maximum power steering pump flow. Although the gears have the capability
to handle this maximum flow, it is not always a system need or requirement. When using combinations of dual gears
or a single gear with a hydraulic linear cylinder, supply flows for both components should be considered (See Steering
Gear Flow Requirements). Single gear applications have a recommended flow at engine idle. For acceptable steering
speed performance, again, refer to the Steering Gear Flow Requirements. Increasing the engine idle flow by more
than 50% of the recommended flow can cause power steering system overheating, vehicle directional control problems (Darting), and steer axle returnability (Non-recovery). If you measure idle flows above the 50% limit, consult your
OEM for guidance and recommendations.
Comment J
Flushing and Air Bleeding the System
IMPORTANT: Clean the area around the reservoir, steering gear and pump thoroughly before beginning this procedure.
1.
2.
3.
4.
5.
6.
Set parking brake on vehicle and block rear wheels.
Raise the front end off the ground
Take vehicle out of gear and put into neutral position
Raise hood and place a drip pan under the steering gear
Remove both the pressure and return lines from the steering gear
Remove filter from the power steering fluid reservoir and discard
IMPORTANT: Discard only the filter, other components may be required to hold filter element in place inside the
reservoir.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Clean the inside of the reservoir
Turn steering wheel from full left to full right 3-4 times. This will purge the oil from the steering gear.
Reconnect pressure and return lines to the steering gear and tighten
Install new filter element into the reservoir
Clean reservoir filler cap with an approved solvent. Inspect gasket and replace if necessary.
Fill reservoir with approved replacement fluid and reinstall the filler cap
Start engine for 10 seconds, stop, and check reservoir fluid level and top off if necessary. You may need to repeat
this procedure 3 or 4 times.
Upon completion of filling the reservoir, start the engine and let it idle. At engine idle, steer full right and full left
once and return to straight ahead. Stop engine and check power steering reservoir level and top off if required.
Restart engine and steer full turns each direction 3 or 4 times.
Stop engine and recheck reservoir fluid level and adjust to correct level, if needed.
Inspect system for leaks and correct if necessary
Bleed air from the system if required (Refer to your steering gear service manual for recommended air bleeding
procedures.)
Remove drip pan and lower vehicle. Remove blocks from wheels and release vehicle for normal service.
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Comment K
Identifying “Burnt Oil”
Sometimes the power steering reservoir oil supply will become hotter than the normal operating temperature and
overheat. This condition may result in an intermittent loss of power assist and also cause deterioration of the power
steering hoses and component seals. TRW recommends that the power steering hoses be examined for deterioration
due to overheated oil, which can be identified by wet hoses, and determine the condition of the reservoir fluid by
looking for signs of “burnt oil.”
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Section 5
Test Results
Test 5 - Power Steering Pump Test .................................. 40
Test 5.1 - 40 Minute Power Steering Pump Test ............. 40
Test 6 - Flow Control Response Test ............................... 41
Test 6.1 - 40 Minute Flow Control Response Test ........... 41
Test 10 - Restricted Hydraulic Line Test ........................... 42
Steering Gear Flow Requirements ................................... 43
Pump Part Number Reference Guide ............................... 44
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Test 5.0 - Power Steering Pump Test
Relief Pressure:
Engine(RPM)
PSI/BAR
No Load
1000PSI
Idle
1500
Table 5.0
Test 5.1 - 40 Minute Power Steering Pump Test
Ambient
Start
10 Minutes
20 Minutes
30 Minutes
40 Minutes
Unit of Measure
890
F or C
Relief Pressure:
Engine(RPM)
PSI/BAR
No Load
Idle
1500
Table 5.1
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steering appendixes
Test 6.0 - Pump Flow Control Response Test
Unit of Measure
PSI or BAR
Unit of Measure
PSI or BAR
Pump Relief #1 (Idle)
Pump Relief #1 (1500 RPM)
Pump Relief #2 (Idle)
Pump Relief #2 (1500 RPM)
Pump Relief #3 (Idle)
Pump Relief #3 (1500 RPM)
Table 6.0
Test 6.1 - 40 Minute Pump Flow Control Response Test
Ambient
Start
10 Minutes
20 Minutes
30 Minutes
40 Minutes
Unit of Measure
Unit of Measure
PSI or BAR
F or C
Unit of Measure
PSI or BAR
Pump Relief #1 (Idle)
Pump Relief #1 (1500 RPM)
Pump Relief #2 (Idle)
Pump Relief #2 (1500 RPM)
Pump Relief #3 (Idle)
Pump Relief #3 (1500 RPM)
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Table 6.1
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Test 10.0 - Restricted Hydraulic Line Test
With PSSA @ 125 - 135 F (52 - 57 C)
RPM
GPM or LPM
With pressure gauge at pressure line to
steering gear at pump end
RPM
GPM or LPM
Remove pressure and return lines and
measure pressure with gauge at pump outlet
RPM
PSI or BAR
Table 10.0
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Steering Gear Flow Requirements
Single Gear
Gear
GPM
LPM
TAS40, THP/PCF45, HFB52
2.2
8.3
TAS55, THP/PCF60
2.6
9.8
TAS65 or HFB64
3.0
11.4
TAS85 or HFB70
3.6
13.6
RCS40
2.2
8.3
RCS55
2.6
9.8
RCS65
3.0
11.4
RCS85
3.6
13.6
GPM
LPM
TAS65 w/ RCS65
6.0
22.7
TAS65 w/ Linear Cylinder
6.5
24.6
TAS85 w/ RCS85
7.0
26.5
TAS85 w/ RCS65
6.5
24.6
TAS85 w/ Linear Cylinder
6.5
24.6
HFB70 w/ RCB70
7.0
26.5
HFB70 w/ RCB64
6.5
24.6
HFB70 w/ Linear Cylinder
6.5
24.6
Dual Gear
Gear
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Pump Part Number Reference Guide
Check the part number on your TRW power steering pump and note the pump relief setting shown in the example
below. (See illustration on where to find the pump part number). If the values that you have recorded are within +/100 psi (+/- 7 bar) your pump is functioning properly. If the values recorded are below the negative tolerance, your
pump is malfunctioning and should be replaced.
For TRW power steering pumps, the relief setting will be the 5th and 6th numbers in the pump part number.
EV 18 12 15 R 1 01 00
Family designation
PS = PS Pump
EV = EV Pump
Displacement per revolution
18 = 18 cc (1.10 cir)
22 = 22 cc (1.34 cir)
25 = 25 cc (1.53 cir)
28 = 28 cc (1.71 cir)
Flow control
12 = 12 lpm (3.17 gpm)
14 = 14 lpm (3.70 gpm)
16 = 16 lpm (4.23 gpm)
20 = 20 lpm (5.28 gpm)
24 = 24 lpm (6.34 gpm)
Relief setting
09 = 90 bar (1305 psi)
10 = 100 bar (1450 psi)
12 = 120 bar (1740 psi)
14 = 140 bar (2030 psi)
15 = 150 bar (2175 psi)
16 = 160 bar (2320 psi)
17 = 170 bar (2465 psi)
18 = 185 bar (2683 psi)
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Direction of rotation
R = clockwise rotation
L = counterclockwise rotation
Shaft type
1 = 11 tooth 16/32 spline
2 = .625 dia. woodruf key
Housing
Varies between PS and EV Series pump
Customer version
00 = Standard
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TRW Automotive
Commercial Steering Systems
800 Heath Street
Lafayette, IN 47904
Tel 765.423.5377
Fax 765.429.1868
http://www.trucksteering.com
http://trucksteering.trw.com
© TRW Inc. 2002
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TRW1250
Rev. 4/02
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