BDR
Service and Repair Manual
BLN-0079
Febuary 2013
TABLE OF CONTENTS
Section
Page
Foreword.......................................................2
Section
Page
BDR Repair..................................................14
How to use this manual.............................14
Description and Operation..........................3
General Instructions...................................14
Introduction..................................................3
Transmission Removal..............................14
General Description.....................................3
Limited Disassembly..................................14
Hydraulic Flow Schematic...........................4 Tools and Torques.....................................15
External Features BDR.............................5-6
BDR Tear Down and Assembly............16-28
Seal Kit Replacement................................16
Product Identification..................................7
Control Arm and Return to Neutral............17
Control Arm Options..................................18
Technical Specifications BDR....................7
Input (Pump) Shaft....................................19
Output (Motor) Shaft..................................20
Safety.............................................................8
Bypass Arm...............................................21
Personal Safety............................................8
Charge Cover............................................22
Tool Safety...................................................8
Lower Housing...........................................23
Work Area Safety.........................................8
Motor Block, Bearing Retainer and Thrust
Bearing......................................................24
Servicing Safety...........................................8
Troubleshooting...........................................9
Center Section...........................................25
Pump Block and Thrust Bearing................26
Swashplate, Trunnion Arm, Slot Guide and
Bypass.......................................................27
Service and Maintenance.....................10-13
Assembly After a Complete Tear Down.....28
External Maintenance................................10
BDR Exploded View..................................29
Service and Maintenance Procedures.......10
BDR Items List..........................................30
Fluids.........................................................10
Fluid Volume and Level.............................10
Fluid Change..............................................11
Purging Procedures...................................12
Return to Neutral Setting...........................13
Glossary of Terms......................................31
FOREWORD
Headquartered in Sullivan, Illinois, Hydro-Gear®
is a world leader in the design, manufacture,
and service of quality hydrostatic transmissions
for the lawn and garden industry. The mission of
our company is to be recognized by our customers and the industry as a world-class supplier
and the quality leader in everything we do.
This Service and Repair Manual is designed
to provide information useful in servicing and
troubleshooting the Hydro-Gear BDR.
Also included is a glossary of terms that are
frequently used throughout the industry and in
Hydro-Gear service publications. Understanding terminology is very important!
It is necessary, and a good shop practice, that
your service area be equipped with the proper
tools and the mechanics be supplied the latest
information available. All repair procedures
illustrated in this guide are suggested, but preferred methods of repair.
Repair procedures require that the transmission
unit be removed from the vehicle.
This is not a certification, test or study guide for
a certification test. If a technician is interested
in certification, they should contact an agent
representing OPEESA (Outdoor Power Equipment and Engine Service Association) at (860)
767-1770 or their Hydro-Gear Central Service
Distributor. Many distributors will be hosting
certification testing. These study guides will
cover most of the products and manufacturers
in our industry.
For more information about Hydro-Gear or our
products, please contact your Central Service
Distributor, or call our Customer Service Department at (217) 728-2581.
2BDR
DESCRIPTION AND OPERATION
INTRODUCTION
The purpose of this manual is to provide information useful in servicing the Hydro-Gear®
BDR. This manual includes the general descriptions, hydraulic schematics, technical
specifications, servicing and troubleshooting
procedures.
The transmission normally will not require servicing during the life of the vehicle in which it
is installed. Should other servicing be required,
the exterior of the transmission will need to be
thoroughly cleaned before beginning most procedures. Do not wash the transmission while
it is hot. Do not use a pressure washer to
clean the unit.
GENERAL DESCRIPTION
The BDR is a self contained unit designed for
the transfer and control of power. It provides an
infinitely variable speed range between zero
and maximum in both forward and reverse
modes of operation.
The BDR uses a variable displacement pump
with a maximum displacement of 10cc per revolution, and motor with a fixed displacement of
21cc per revolution. The variable displacement
pump features a trunnion mounted swashplate
with a direct-proportional displacement control.
Reversing the direction of the swashplate reverses the flow of oil from the pump and thus
reverses the direction of the motor output rotation. The pump and motor are of the axial piston design and utilize spherical nosed pistons
which are held against a thrust race by internal
compression springs.
The BDR has a self contained fluid supply. The
fluid is forced through the filter by a positive
“head” on the fluid in the housing/expansion
tank with an assist by the negative pressure
created in the pump pistons as they operate.
The check valves in the center section are used
to control the make-up flow of the fluid to the
low pressure side of the loop.
A cam style, block lifting bypass is utilized in
the BDR to permit moving the vehicle for a short
distance at a maximum of 2 m.p.h. (3.2 Km/h)
without starting the engine.
WARNING
Actuating the bypass will result in the
loss of hydrostatic braking capacity. The
machine must be stationary on a level
surface and in neutral when actuating
the bypass.
BDR3
HYDRAULIC FLOW SCHEMATIC
Figure 1. Hydraulic Flow Illustration
HYDRAULIC SCHEMATIC
Figure 1 provides an illustration of the hydraulic
oil circuit.
The input shaft and pump cylinder block are
turned in one direction only by the engine/drive
belt/pulley combination. Output of the oil flow is
controlled by the direction and amount that the
variable swashplate is angled. As the pump pistons compress they force the oil to flow through
one of two passageways (forward or reverse)
in the center section to the motor cylinder block
and motor shaft. Since the motor has a fixed
displacement angle it is forced to turn with the
flow of oil. As the angle of the pump swashplate
is increased the amount of oil being pumped
will increase and cause a higher speed output
of the motor. Reversing the angle of the pump
swashplate will reverse the direction of oil flow.
During the operation of the transmission, fluid
is “lost” from the hydraulic loop through leak
paths designed into the product for lubrication
purposes (around pistons, under the rotating
cylinder blocks, etc.). This “lost” fluid returns to
the transmission housing, then is pulled back
into one of the check valves depending upon
the direction of vehicle operation.
The motor cylinder block mounts onto a splined
motor shaft which drives the gear train.
The bypass feature in the BDR has a mechanical lever which lifts the motor block off of the
center section running surface. This allows oil
flow from the cylinder blocks to be discharged.
4BDR
EXTERNAL FEATURES BDR
Input (Pump) Shaft
Bypass Arm
Output (Motor) shaft
Control Arm
Fill Port
Input (Pump) Shaft
Control Arm
Output (Motor) Shaft
Bypass Arm
Figure 2. External Features
BDR5
EXTERNAL FEATURES BDR
Bypass Arm
Output (Motor) Shaft
Input (Pump) Shaft
Charge Cover
Control Arm
Figure 3. External Features
6BDR
TECHNICAL SPECIFICATIONS
Charged
Displacement
Variable Pump (Maximum)
10.2 cc/rev
.62 in3/rev
Fixed Motor
21.8 cc/rev
1.33 in3/rev
Input Speeds
Maximum Unloaded
Minimum Loaded
System Operating Pressure
Intermittent
Continuous
Case Pressure
Non Charged
3600 rpm
1800 rpm
3000 rpm
1800 rpm
2100 psi
145 bar
2100 psi
145 bar
1000 psi
70 bar
850 psi
60 bar
Continuous
8 psi
0.6 bar
Maximum at Cold Start
15 psi
1.0 bar
15 lbs
6.8 kg
Weight
180 in-lb / 1000 psi
20.3 N-m / 70 bar
Motor Output Torque
(Approximate)
1.9 cc/rev
Charge Pump
Displacements
-----
.11 in3/rev
Table 1. Technical Specifications
PRODUCT IDENTIFICATION
The model and configuration of the BDR can be determined from the label shown in Figure 3.
HYDRO-GEAR
BOM Mo
del Num
ber
ilt
u
Year B
BDR-320
2 275 B1 476 -001
Date (Julian- Day of year)
Assembled in USA
Serial Number (unique for that model - for that day)
Type of Product and Build Information
Figure 3. Configuration Label
BDR7
SAFETY
This symbol points out important safety
instructions which, if not followed, could endanger the personal safety and/or property of yourself and others. Read and follow all instructions in this manual before attempting maintenance on your transmission. When you see this
symbol - HEED ITS WARNING.
WARNING
POTENTIAL FOR SERIOUS INJURY
Inattention to proper safety, operation,
or maintenance procedures could result
in personal injury, or damage to the
equipment. Before servicing or repairing the BDR, fully read and understand
the safety precautions described in this
section.
PERSONAL SAFETY
Certain safety precautions must be observed
while servicing or repairing the BDR. This
section addresses some of these precautions
but must not be considered an all-inclusive
source on safety information. This section is
to be used in conjunction with all other safety
material which may apply, such as:
1) Other manuals pertaining to this machine,
2) Local and shop safety rules and codes,
3) Governmental safety laws and regulations.
Be sure that you know and understand the
equipment and the hazards associated with it.
Do not place speed above safety.
Notify your supervisor whenever you feel there
is any hazard involving the equipment or the
performance of your job.
Never allow untrained or unauthorized personnel to service or repair the equipment.
Wear appropriate clothing. Loose or hanging
clothing or jewelry can be hazardous. Use the
appropriate safety equipment, such as eye
and hearing protection, and safety-toe and
slip-proof shoes.
Never use compressed air to clean debris from
yourself or your clothing.
TOOL SAFETY
Use the proper tools and equipment for the task.
Inspect each tool before use and replace any
tool that may be damaged or defective.
WORK AREA SAFETY
Keep the work area neat and orderly. Be sure
it is well lit, that extra tools are put away, trash
and refuse are in the proper containers, and dirt
or debris have been removed from the working
areas of the machine.
The floor should be clean and dry, and all extension cords or similar trip hazards should be
removed.
SERVICING SAFETY
Certain procedures may require the vehicle to
be disabled in order to prevent possible injury
to the servicing technician and/or bystanders.
The loss of hydrostatic drive line power may
result in the loss of hydrostatic braking capability.
Some cleaning solvents are flammable. Use
only approved cleaning materials: Do not use
explosive or flammable liquids to clean the
equipment.
To avoid possible fire, do not use cleaning
solvents in an area where a source of ignition
may be present.
Discard used cleaning material in the appropriate containers.
8BDR
TROUBLESHOOTING
Follow all safety procedures outlined in
the vehicle owner’s manual.
In many cases, problems with the BDR are
not related to a defective transmission, but are
caused by slipping drive belts, partially engaged
bypass valves, and loose or damaged control
linkages. Be sure to perform all operational
checks and adjustments outlined in the Service
and Maintenance section before assuming the
transmission is malfunctioning. Table 5 below
provides a troubleshooting checklist to help
determine the cause of operational problems.
Possible Cause
Corrective Action
WARNING
Do not attempt any servicing or adjustments with the engine running.
Use extreme caution while inspecting
the drive belt assembly and all vehicle
linkage!
UNIT OPERATES IN ONE DIRECTION ONLY
Control linkage bent or out of adjustment
Drive belt slipping or pulley damaged
Repair or replace linkage
Repair or replace drive belt or pulley
VEHICLE DOES NOT DRIVE/TRACK STRAIGHT
Vehicle tires improperly inflated
Control linkage bent or out of adjustment
Bypass assembly sticking
Refer to vehicle manufacturer suggested pressure
Repair or replace linkage
Repair or replace bypass
UNIT IS NOISY
Oil level low or contaminated oil
Excessive loading
Loose parts
Bypass assembly sticking
Air trapped in hydraulic system
Fill to proper level or change oil
Reduce vehicle loading
Repair or replace loose parts
Repair or replace linkage
Purge hydraulic system
UNIT HAS NO/LOW POWER
Engine speed low
Control linkage bent or out of adjustment
Drive belt slipping or pulley damaged
Oil level low or contaminated oil
Excessive loading
Bypass assembly sticking
Air trapped in hydraulic system
Adjust to correct setting
Repair or replace linkage
Repair or replace drive belt or pulley
Fill to proper level or change oil
Reduce vehicle loading
Repair or replace linkage
Purge hydraulic system
UNIT IS OPERATING HOT
Debris buildup around transmission
Cooling fan damaged
Oil level low or contaminated oil
Excessive loading
Air trapped in hydraulic system
Clean off debris
Repair or replace cooling fan
Fill to proper level or change oil
Reduce vehicle loading
Purge hydraulic system
TRANSMISSION LEAKS OIL
Damaged seals, housing, or gaskets
Air trapped in hydraulic system
Replace damaged component
Purge hydraulic system
Table 4. BDR Troubleshooting Guide
BDR9
SERVICE AND MAINTENANCE
NOTE: Any servicing dealer attempting
a warranty repair must have prior approval before conducting maintenance
of a Hydro-Gear® product unless the
servicing dealer is a current Authorized
Hydro-Gear Service Center.
EXTERNAL MAINTENANCE
Regular external maintenance of the BDR
should include the following:
1. Check the vehicle operator’s manual for
the recommended load ratings. Insure
that the current application does not
exceed load rating.
2. Check oil level in accordance with Figure 4
Page 11.
3. Inspect the vehicle drive belt, idler pulley(s),
and idler spring(s). Insure that no belt slippage can occur. Slippage can cause low
input speed to the transmission.
4. Inspect the vehicle control linkage to the
directional control arm on the transmission.
Also insure that the control arm is securely
fastened to the trunnion arm of the transmission.
FLUIDS
The fluids used in Hydro-Gear products have
been carefully selected, and only equivalent, or
better products should be substituted.
Typically, an engine oil with a minimum rating
of 9.0 cSt (55 SUS) at 230° F (110° C) and an
API classification of SL is recommended. A
20W50 engine oil has been selected for use
by the factory and is recommended for normal
operating procedures.
FLUID VOLUME AND LEVEL
Fluid volume information is provided in Table
6, page 11.
Certain situations may require additional fluid
to be added or even replaced. Refer to page 5
for the proper fill port location.
A volume of 37.87 fluid ounces should bring
the fluid to the correct level in the transmission.
Recheck the fluid level once the unit has been
operated for approximately 1 minute.
Purging will be required. Refer to the purging
procedures on Page 12.
5. Inspect the bypass mechanism on the transmission and the vehicle linkage to insure
that both actuate and release fully.
SERVICE AND MAINTENANCE
PROCEDURES
Some of the service procedures presented on
the following pages can be performed while the
transmission is mounted on the vehicle. Any
repair procedures as mentioned in the repair
section of this manual must be performed after
the unit has been removed from the vehicle.
The unit should be thoroughly cleaned before
any service procedures are performed.
10BDR
FLUID CHANGE
FLUID CHANGE PROCEDURE
In the event of oil contamination or degradation,
oil addition or change may alleviate certain performance problems. Refer to the vehicle manufacturer’s recommended oil change frequency.
5. Fill the transmission at the oil fill port according to Figure 4.
1. Remove the transmission from the vehicle.
7. Purging will be required. Refer to the purging
procedures on Page 12.
2. Clean the oil fill port area of any debris.
3. Remove the oil fill port fitting.
4. Position the transmission so the oil will drain
completely out of the housing.
6. Install the oil fill port fitting.
8. Recheck the fluid level once the unit has
been operated for approximately 1 minute.
Fluid Description
20W50
Volume
37.87 fluid ounces
Table 6. Fluid Volumes for the BDR
Fill Port
Oil Level 1.5 inches max
Figure 4. Oil Level
BDR11
PURGING PROCEDURES
Due to the effects air has on efficiency in hydrostatic drive applications, it is critical that it is
purged from the system.
Before starting, make sure the transmission
is at the proper oil level. If it is not, fill to the
specifications outlined on Page 11, Table 6.
These purge procedures should be implemented any time a hydrostatic system has
been opened to facilitate maintenance or any
additional oil has been added to the system.
The following procedures should be performed
with the vehicle drive wheels off the ground,
then repeated under normal operating conditions.
Air creates inefficiency because its compression and expansion rate is higher than that of
the oil approved for use in hydrostatic drive
systems.
1. With the bypass valve open and the engine
running, slowly move the directional control
in both forward and reverse directions (5 or
6 times), as air is purged from the unit, the
oil level will drop.
The resulting symptoms in hydrostatic systems
may be:
1. Noisy operation.
2. Lack of power or drive after short term operation.
3. High operation temperature and excessive
expansion of oil.
2. With the bypass valve closed and the engine
running, slowly move the directional control
in both forward and reverse directions (5 to
6 times). Check the oil level, and add oil as
required after stopping the engine.
3. It may be necessary to repeat Steps 1 and
2 until all the air is completely purged from
the system. When the transmission moves
forward and reverse at normal speed purging is complete.
12BDR
RETURN TO NEUTRAL SETTING
WARNING
WARNING
POTENTIAL FOR SERIOUS INJURY
Do not attempt any servicing or adjustments with the engine running.
Use extreme caution while inspecting
the drive belt assembly and all vehicle
linkage!
Inattention to proper safety, operation,
or maintenance procedures could result
in personal injury, or damage to the
equipment. Before servicing or repairing the BDR, fully read and understand
the safety precautions described in this
section.
The return to neutral mechanism on the transmission is designed to set the directional control into a neutral position when the operator
releases the vehicle hand control. Follow the
procedures below to properly adjust the return
to neutral mechanism on the transmission:
1. Confirm the transmission is in the operating
mode (bypass disengaged). Raise the vehicle’s
drive tires off the ground to allow free rotation.
2. Remove the Original Equipment Manufacturer’s (OEM’s) control linkage at the control arm.
Refer to Figure 5.
3. Start the engine and increase the throttle to
full engine speed.
Follow all safety procedures outlined in
the vehicle owner’s manual.
5. Stop the vehicle’s engine. Reattach and
adjust the OEM linkage according to Step 3
and Step 4. Stop the vehicle engine. Refer
to Figure 5.
6. Note the axle directional movement. Stop
the vehicle engine. Loosen the RTN adjustment screw until the control arm can be rotated.
Rotate the control arm in the opposite direction
of the wheel rotation in 5 degree increments.
Tighten the RTN adjustment screw. Refer to
Table 8, Required Torque Values, page 15.
Recheck according to steps 3 and 4. Stop
the vehicle engine. Reattach and adjust the
OEM linkage according to the OEM manual.
Recheck according to steps 3 and 4. Refer to
Figure 5.
4. Check for axle rotation. If the axle does not
rotate, go to Step 5. If the axle rotates, go to
Step 6.
Speed and Directional
Control Arm
RTN Adjustment Screw
Figure 5. Return to Neutral Setting
BDR13
BDR REPAIR
HOW TO USE THIS MANUAL
Each subassembly illustrated in this section is
illustrated with an exploded view showing the
parts involved. The item reference numbers
in each illustration are for assembly instructions only. See page 30 for part names and
descriptions. A complete exploded view and
item list of the transmission is provided at the
end of the repair section.
GENERAL INSTRUCTIONS
Cleanliness is a primary means of assuring
satisfactory life on repaired units. Thoroughly
clean all exposed surfaces prior to any type
of maintenance. Cleaning of all parts by using a solvent wash and air drying is usually
adequate. As with any precision equipment,
all parts must be kept free of foreign material
and chemicals.
Protect all exposed sealing surfaces and open
cavities from damage and foreign material. The
external surfaces should be cleaned before
beginning any repairs.
Upon removal, it is recommended that all seals,
O-rings, and gaskets be replaced. During
installation lightly lubricate all seals, O-rings
and gaskets with a clean petroleum jelly prior
to assembly. Also protect the inner diameter of
seals by covering the shaft with a cellophane
(plastic wrap, etc.) material.
Parts requiring replacement must be replaced
from the appropriate kits identified in the Items
Listing, found at the end of this manual. Use
only original Hydro-Gear® replacement parts
found at the Hydro-Gear website (www.hydrogear.com).
TRANSMISSION REMOVAL
It is necessary to remove the transmission from
the vehicle before performing the repair procedures presented in this section.
LIMITED DISASSEMBLY
The following procedures are presented in
the order in which they must be performed to
completely disassemble the unit. Do not disassemble the unit any farther than is necessary
to accomplish the required repairs. Each disassembly procedure is followed by a corresponding assembly procedure.
Reassembly is accomplished by performing
the “Assembly” portions of the procedures. If
the unit has been completely disassembled, a
summary of the assembly procedures, in the
order in which they should occur, is given on
page 28.
14BDR
TOOLS AND TORQUES
Miscellaneous
Service & Repair Manual
Flat Blade Screw Driver (2)
Torque Wrench
Air Impact Wrench
Rubber Mallet
Breaker Bar
Plastic Putty Knife
Large External Snap Ring
Small Internal Snap Ring
Sockets
1/2”-3/8” Adapter
3/8” Deep
1/2” Deep
7/16” Deep
9/16” Deep
13/16” Deep
7/8”
E8 Torx
T-25 Torx
Table 7. Required Tools
Operation
Torque
Item
Description
Control Arm
See Page 16-17
35
Nut
Center Section Screws
525-700 in-lbs (60-79 Nm)
44
Screw
Housing Screws
135-185 in-lbs (16-20 Nm)
50
Screw, Self Tapping
Plug
180-240 in-lbs (21-27 Nm)
51
Plug
Charge Cover Screws
87-108 in-lbs (10-12 Nm)
55
Screw
Charge Relief
42-62 in-lbs (5-7 Nm)
57
Bolt, Self Tapping
Charge Cover Plug
6-24 in-lbs (.67-2.7 Nm)
60
Plug
Control Arm
210-270 in-lbs (24-30 Nm)
76
Screw
Plug
6-24 in-lbs (.67-2.7 Nm)
202
Plug
Table 8. Required Torque Values
BDR15
SEAL KIT REPLACEMENT
Before disassembly, wipe the unit free of any
debris to avoid contamination.
Trunnion Seal (page 17 & 18)
1. Remove the control arm and any attachments to the control arm. See page 18.
2. Remove retaining ring (58) and discard.
3. The seal (33) can be replaced by following
steps 2-5 of the procedure used to replace
the input shaft.
4. Install new retaining ring (58).
5. Install the control arm and any attachments
to the control arm.
Input (Pump) Seal (page 19)
1. Remove the seal retaining ring (7).
2. Carefully pull the input seal (4) out of the
housing bore with a “hook” type tool and discard. Care must be taken to avoid damage
to the housing bore or shaft sealing area.
3. Lubricate the new seal with petroleum jelly
prior to installation.
4. Wrap the shaft keyway (splines) with cellophane to prevent damage to the seal lip
during installation.
5. Slide the seal over the shaft and press it into
the housing bore.
6. The seal should seat against the spacer.
7. Install the seal retaining ring (7) and make
sure it is fully seated in its groove.
Output (Motor) Seal (page 20)
1. The seal (66) can be replaced by following
steps 1-7 of the procedure used to replace
the input seal.
Bypass Seal (page 21)
1. Remove the bypass arm and any attachments to the bypass arm. See page 21.
2. Remove the seal retaining ring (58). Remove the bypass rod seal (40) out of the
housing bore with a “hook” type tool. Care
must be taken to avoid damage to the housing bore or the bypass actuator.
3. The seal (40) can be replaced by following
steps 3-5 of the procedure used to replace
the input shaft.
4. Install the bypass arm (41).
5. Install the seal retaining ring (42).
Charge Cover O-Ring (page 22)
1. Mark the orientation of the charge cover
(54). It is very important that the charge
cover is reinstalled the same way it was
taken off.
2. Replace the o-ring (53)
5. Install the charge cover (54) and bolts (55)
see page 15 for torque value.
Lower Housing Gasket (page 23)
1. Mark the orientation of the charge cover (54)
and remove. It is very important that the
charge cover is reinstalled the same way it
was taken off.
2. Remove o-ring (53) and geroter (52) and set
aside.
3. Remove lower housing (2).
4. Remove gasket (49) discard and install new
gasket.
5. Install lower housing (2) reference page 15
for torque values for the housing bolts (9).
6. Install o-ring (53) and geroter set (52).
7. Install charge cover (54) and bolts (55).
16BDR
TRUNNION SEAL (RETURN TO NEUTRAL)
Refer to Figure 6.
Prior to disassembly, note the position of the
scissor arm brackets and the tab on the outer
control arm bracket.
Inspection
1. Inspect all parts of damage, corrosion, or
wear.
Disassembly
Assembly
CAUTION: The spring used on the return to
neutral linkage is under tension. To avoid
possible injury use car and properly protection
turning disassembly and assembly of the return
to neutral linkage.
1. Install seal (33) and retaining ring (58).
1. Loosen (but do not remove) the nut (35).
2. To relieve spring tension, carefully pry up on
the out scissor control arm until it releases
from the tab on the control arm (34).
3. Remove the spring (81), the nut (35) and
washer (104).
4. Remove the scissors arm assembly (80).
2. Install return arm (74).
3. Install washer (59) and bolt (76) see torque
value below.
4. Install control arm (34).
5. Install scissors arm kit (80).
6. Install washer (59) and nut (35) see torque
value below.
7. Install spring (81).
8. See page 13 to adjust neutral setting.
5. Remove control arm (34).
6. Remove the bolt (76) and washer (59).
7. Remove the return arm (74).
8. Remove and discard the retaining ring (58)
and seal (33) only if replacing the seal or
doing a complete rebuild.
Item
Torque
76
210-270 in-lbs (24-30 Nm)
35
180-240 in-lbs (21-27 Nm)
See page 15 for full torque value chart.
Figure 6. Control Arm and Return to Neutral
BDR17
TRUNNION SEAL (CONTROL ARM)
Refer to Figure 7.
Disassembly
Assembly
1. Remove nut (35).
1. Install seal (33) and retaining ring (58).
2. Remove washer (59).
2. Instal stud (36) see torque value below and
washer (37).
3. Remove nut (35B) / set screw (72).
3. Install control arm (34).
4. Remove control arm (34).
5. Remove washer (37).
4. Instal nut (35B) / set screw (72) see torque
values below.
6. Remove stud (36) only if damaged or doing
a complete rebuild.
5. Install washer (59).
7. Remove and discard the retaining ring (58)
and seal (33) only if replacing the seal or
doing a complete rebuild.
6. Install nut (35) after setting neutral. See
torque values below.
Inspection
1. Inspect all parts of damage, corrosion, or
wear.
Item
Torque
76
210-270 in-lbs (24-30 Nm)
35
85-120 in-lbs (10-13.5 Nm)
35B
180-240 in-lbs (21-27 Nm)
72
100-185 in-lbs (12-20 Nm)
36
50-120 in-lbs (6-13.5 Nm)
See page 15 for full torque value chart.
OR
B
Figure 7. Control Arm
18BDR
INPUT (PUMP) SHAFT
Refer to Figure 8.
Disassembly
1. Requires removal of all items beginning on
page 16.
2. Remove the retaining ring (7).
5. Slide the seal over the shaft and press it
into the housing bore.
6. The seal should seat against the spacer.
7. Install the seal retaining ring (7) and make
sure it is fully seated in its groove.
3. Remove the lip seal (4) and discard.
4. Remove the washer (5).
5. Remove the pump shaft assembly (12).
Inspection
1. Inspect the components for wear or damage.
Assembly
Note: If the unit is charge mark the orientation
of the charge cover and then remove before
reinstalling the input shaft. See page 28 for
complete rebuild instructions.
1. Install input shaft (12).
2. Install washer (5).
3. Lubricate the new seal (5) with petroleum
jelly prior to installation.
4. Wrap the shaft keyway (splines) with cellophane to prevent damage to the seal lip
during installation.
Figure 8. Input (Pump) Shaft
BDR19
OUTPUT (MOTOR) SHAFT
Refer to Figure 9.
Disassembly
1. Requires removal of all items beginning on
page 16.
2. Remove the retaining ring (28).
3. Remove the lip seal (66) and discard.
4. Remove the washer (69).
5. Remove the pump shaft assembly (24).
Inspection
1. Inspect the components for wear or damage.
Assembly
Note: See page 28 for complete rebuild instructions.
1. Install input shaft (24).
2. Install washer (69).
3. Lubricate the new seal (66) with petroleum
jelly prior to installation.
4. Wrap the shaft keyway (splines) with cellophane to prevent damage to the seal lip
during installation.
5. Slide the seal over the shaft and press it into
the housing bore.
6. The seal should seat against the spacer.
7. Install the seal retaining ring (28) and make
sure it is fully seated in its groove.
Figure 9. Motor Shaft
20BDR
BYPASS ARM
Refer to Figure 10.
Assembly
Disassembly
Note: See page 28 for complete rebuild instructions.
1. Remove the retaining ring (42).
2. Remove the bypass arm (40).
1. Lubricate the new seal (40) with petroleum
jelly prior to installation.
3. Remove and discard the retaining ring (58)
and seal (40) only if replacing the seal or
doing a complete rebuild.
2. Wrap the shaft keyway (splines) with cellophane to prevent damage to the seal lip
during installation.
Inspection
3. Slide the seal over the shaft and press it into
the housing bore.
1. Inspect the components for wear or damage.
4. Install retaining ring (58).
5. Install bypass arm (41).
6. Install retaining ring (42).
Figure 10. Bypass Arm
BDR21
CHARGE COVER
Refer to Figure 11.
Disassembly
Assembly
1. Mark the orientation of the charge cover
(54). It is very important that the charge
cover is reinstalled the same way it was
taken off.
Note: See page 28 for complete rebuild instructions.
1. Install the o-ring (53).
2. Install the gerotor (52).
2. Remove the bolts (55).
3. Install the charge cover (54). It is very important that the charge cover is reinstalled
the same way it was taken off.
3. Remove the charge cover (54).
4. Remove gerotor (52).
4. Install the bolts (55) see page 15 for torque
value.
5. Remove o-ring (53).
Inspection
1. Inspect the charge cover o-ring and running
surface for wear or damage.
Note: The charge
cover orientation will
vary by model number. Mark the orientation of the charge
cover with a paint
pen or permanent
marker before disassembly.
Figure 11. Charge Cover
*
22BDR
LOWER HOUSING
Refer to figure 12.
Disassembly
Assembly
1. Requires removal of all items beginning on
page 16.
Note: See page 28 for complete rebuild instructions.
2. Remove the housing bolts (50).
1. Install new gasket (49).
3. Remove and discard the gasket (49).
2. Install lower housing (2).
Inspection
3. Install bolts (50) see page 15 for torque
values.
1. Inspect the bearing and bushing areas of
the side cover.
*
*
Figure 12. Bottom Cover
BDR23
MOTOR BLOCK, BEARING RETAINER AND THRUST BEARING
Refer to Figures 13 A and 13 B.
Disassembly
1. Requires removal of all items beginning on
page 16.
2. Remove the bearing retainer (29).
3. Remove the thrust bearing (25) and block
kit (21) but inserting a plastic putty knife
between the housing and the thrust bearing. Use caution to avoid damaging the
components.
2. Inspect the block running surfaces. NOTE:
These “sealing” surfaces (see Figure 13 B)
should be smooth in appearance without
scratches, scoring, nicks or abrasions. Drag
a fingernail across the surface to detect
uneven wear or scratches which may not
be visible.
Assembly
Note: See page 28 for complete rebuild instructions.
Inspection
1. Disassemble the motor cylinder block assembly (21). Check each piston for proper
operation by pressing the pistons in and releasing them in the block bore. Disassemble
the motor cylinder block. Check for piston/
block wear in the cylinder bore. Inspect the
pistons, piston springs and thrust washers for excessive wear or damage. NOTE:
Thrust washers may be held in place in the
piston by residual oil.
1. Ensure that the bypass plate (38) is in the
center section (3) see page 24.
2. Coat the pump running surface with clean
motor oil.
3. Place the thrust bearing (25) on the block
kit (21) making sure the thick race is against
the pistons.
4. Use a plastic putty knife between the housing (1) and the thrust bearing to depress the
pistons allowing the thrust bearing and block
kit to slid into position.
Note: Care must be taken to
prevent the scaring or scratching
of the center section sealing face
during this step.
Figure 13 B.
Figure 13 A.
24BDR
CENTER SECTION
Refer to Figures 14 A and 14 B.
Disassembly
Inspection
1. Remove the check valves (45). Make a
mark to ensure they are installed back into
the correct ports during assembly.
1. Inspect the center section block running
surfaces. Note: These “sealing” surfaces
(see Figure 14 B) should be smooth in appearance without scratches, scoring, nicks
or abrasions. Drag a fingernail across the
surface to detect uneven wear or scratches
which may not be visible.
2. Remove the bolt (57), the relief plate (56),
the charge ball (47) and spring (46).
3. Remove the center section bolts (44).
4. Remove the center section (3).
5. Remove the bypass plate (38).
6. Remove the pins (43).
2. Inspect the threaded check plug ports of the
center section for debris or damage.
Assembly
Note: See page 28 for complete rebuild instructions.
1. Install the pins (43).
2. Install the bypass plate (38) into the center
section (3).
3. Install the bolts (44). See page 15 for torque
values.
4. Install the spring (46), the charge relief ball
(47), the relief plate (56) and the bolt (57).
See page 15 for torque values.
5. Install the check valves (45) referencing the
marks to ensure they are installed back into
the correct port. See page 15 for torque
values.
6. Install o-ring (48).
*
*
Figure 14 A Center Section
*
Figure 14 B Running Surface Close Up
BDR25
PUMP BLOCK AND THRUST BEARING
Refer to Figure 15.
Disassembly
1. Remove the pump block (15).
2. Remove the thrust bearing (11).
Inspection
1. Disassemble the pump cylinder block assembly (4). Check each piston for proper
operation by pressing the pistons in and releasing them in the block bore. Disassemble
the motor cylinder block. Check for piston/
block wear in the cylinder bore. Inspect the
pistons, piston springs and thrust washers
for excessive wear or damage. Note: Thrust
washers may be held in place in the piston
by residual oil.
2. Inspect the block running surfaces. Note:
These “sealing” surfaces (see figure 13 B)
should be smooth in appearance without
scratches, scoring, nicks or abrasions. Drag
a fingernail across the surface to detect
uneven wear or scratches which may not
be visible.
Assembly
Note: See page 28 for complete rebuild instructions.
1. Install pump shaft first see page 18.
2. Install thrust bearing (11) with thick race
against the pistons.
3. Install the block kit (15).
Figure 15. Pump Block and Thrust Bearing
26BDR
SWASHPLATE, TRUNNION ARM, SLOT GUIDE AND
BYPASS
Refer to Figure 16.
Disassembly
Assembly
1. Remove swashplate (10).
Note: See page 28 for complete rebuild instructions.
2. Remove slot guide (30).
3. Remove bypass actuator (39).
4. Remove trunnion arm (31).
Inspection
1. Inspect the components, bearing and bushing areas for wear or damage.
1. Install pump shaft first. See page 18.
2. Install trunnion arm (31).
3. Install slot guide (30).
4. Install bypass actuator (39).
5. Install swashplate (10).
Figure 15. Pump Block and Thrust Bearing
BDR27
ASSEMBLY AFTER A COMPLETE TEAR DOWN
If the unit has been torn down completely, the
following summary identifies the assembly procedures necessary to completely assemble the
unit. Each assembly procedure is located by a
page reference.
The part reference numbers provided in each
assembly procedure are keyed to the individual
exploded views, and are also keyed to the complete unit exploded view on page 29.
1. Install the input shaft (12), washer (5),
seal (4) and retaining ring (7). Turn until
over and install the thrust washer (13) and
spring (14). See page 19.
2. Install the trunnion arm (31), slot guide
(30), bypass actuator (39) and swashplate
(10). See page 27.
3. Install the thrust bearing (11) with the thick
race towards the pistons and the pump
block kit (15). See page 26.
4. Install pins (43). Install the bypass plate
(38) into the center section (3). Installing the center section (3) and bolts (44).
Install the spring (46), charge relief ball
(47)m relief plate (56) and bolt (57). Install the check valves (45) into the correct
ports. Install o-ring (48). See page 15 for
torque values and page 25 for detailed assembly procedure.
5. Verify that the bypass plate (38) is correctly positioned in the center section
(3). Using a plastic putty knife between
the housing (1) and the thrust bearing
(25) with the thick race toward the pistons
apply pressure to the pistons of the block
kit (21) in order to slid both pieces into
the house. Care must be taken to avoid
damaging the surfaces. Install bearing
retainer (29). See page 24.
6. Install the motor shaft (24), washer (69),
seal (66) and retaining ring (28). See
page 20.
7. Install new housing gasket (49), install
lowering housing (2) and bolts (50). See
page 15 for torque values and page 23 for
detailed assembly procedure.
8. Install o-ring (53) and gerotor (52). Make
sure the charge cover (54) is installed the
same way it was taken off. Install bolts
(55) see page 15 for torque values and
page 22 for detailed assembly procedure.
9. Install bypass seal (40), retaining ring
(58), bypass arm (41) and retaining ring
(42). See page 21.
10.See page 17 and 18 for detailed assembly
procedure of the control arm.
28BDR
BDR EXPLODED VIEW
*
*
*
*
*
*
*
*
*
*
Figure 26. BDR®
BDR29
BDR ITEMS LIST
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
DESCRIPTION
No.
DESCRIPTION
Housing, Upper -Only available in Upper
Housing Kit
Housing, Lower
Center Section - Only available in Center
Section Kit
Lip Seal
Spacer
Wire Retaining Ring
Retaining Ring
Ball Bearing
Cradle Bearing -Only available in Upper
Housing Kit
Swashplate
Thrust Bearing
Pump Shaft
Block Thrust Washer
Block Spring
Pump Cylinder Block 10cc - Only available in
Pump Block Kit
Piston 10cc - Only available in Pump Block
Kit
Piston Spring 10cc- Only available in Pump
Block Kit
Piston Seat Washers - Only available in
Block Kits
Bearing Jrnl - Only available in Center Section Kit
Bushing - Only available in Center Section
Kit
Cylinder Block 21cc- Only available in Motor
Block Kit
Piston 21cc - Only available in Motor Block
Kit
Piston Springs 21cc - Only available in Motor
Block Kit
Output (Motor) Shaft
Thrust Bearing
Ball Bearing
Wire Retaining Ring
Retaining Ring
29
30
31
Retainer, Motor Bearing
Slot Guide
Trunnion Arm
Trunnion Bushing -Only available in Upper
Housing Kit
Lip Seal
Control Arm
Nut, Lock
Bypass Plate - Only available in Center Section Kit
Bypass Actuator
Lip Seal
Bypass Arm
Retaining Ring
Pin
Screw
Check Plug Assembly - Only available in
Center Section Kit
Spring, Charge Relief
Ball
O-Ring
Gasket
Screw, Self Tapping
Plug
Gerotor
O-ring
Charge Pump
Screw
Relief Plate
Bolt, Self Tapping
Retaining Ring
Washer
Plug
Lip Seal
Spacer
Return Arm
Screw
Scissors Arm Assembly
Spring, Extension
Hydro-Gear Label
Plug
32
33
34
35
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
66
69
74
76
80
81
200
202
30BDR
GLOSSARY OF TERMS
Axial Piston: Type of design for hydraulic motors and pumps in which the pistons are arranged
parallel with the spindle (input or output shaft).
Bypass Valve: A valve whose primary function is to open a path for the fluid to bypass the motor
or pump. Also referred to occasionally as the freewheel valve or dump valve.
Case Drain Line (Return Line): A line returning fluid from the component housing to the reservoir.
Cavitation: A concentrated gaseous condition within the fluid causing the rapid implosion of a
gaseous bubble.
Center Section: A device which acts as the valve body and manifold of the transmission.
Charge Pump: A device which supplies replenishing fluid to the fluid power system (closed loop).
Charge Pressure: The pressure at which replenishing fluid is forced into a fluid power system.
Charge Relief Valve: A pressure control valve whose primary function is to limit pressure in the
charge circuit.
Check Valve: A valve whose primary function is to restrict flow in one direction.
Closed Loop: A sealed and uninterrupted circulating path for fluid flow from the pump to the
motor and back.
Decay Rate: The ratio of pressure decay over time.
End Cap: See “Center Section.”
Entrained Air: A mechanically generated mixture of air bubbles having a tendency to separate
from the liquid phase.
Gerotor: A formed rotor set operating about an eccentric that provides a fixed displacement for
pumps or motors.
Hydraulic Motor: A device which converts hydraulic fluid power into mechanical force and motion by transfer of flow under pressure.
Hydraulic Pump: A device which converts mechanical force and motion into hydraulic fluid power
by producing flow.
Hydrostatic Pump: See “Hydraulic Pump.”
Hydrostatic Transaxle: A multi component assembly including a gear case and a hydrostatitransmission.
Hydrostatic Transmission: The combination of a hydraulic pump and motor in one housing to
form a device for the control and transfer of power.
Inlet Line: A supply line to the pump.
BDR31
Integrated Zero-Turn Transaxle: The combination of a hydrostatic transmission and gear case
in one housing to form a complete transaxle.
Manifold: A conductor which provides multiple connection ports.
Neutral: Typically described as a condition in which fluid flow and system pressure is below that
which is required to turn the output shaft of the motor.
Pressure Decay: A falling pressure.
Priming: The filling of the charge circuit and closed loop of the fluid power system during start
up, frequently achieved by pressurizing the fluid in the inlet line.
Purging: The act of replacing air with fluid in a fluid power system by forcing fluid into all of the
components and allowing the air a path of escape.
Rated Flow: The maximum flow that the power supply system is capable of maintaining at a
specific operating pressure.
Scoring: Scratches in the direction of motion of mechanical parts caused by abrasive contaminants.
Swash Plate: A mechanical device used to control the displacement of the pump pistons in a
fluid power system.
System Charge Check Valve: A valve controlling the replenishing flow of fluid from a charge
circuit to the closed loop in a fluid power system.
System Pressure: The pressure which overcomes the total resistance in a system, including all
efficiency losses.
Valve: A device which controls fluid flow direction, pressure, or flow rate.
Variable Displacement Pump: A pump in which the displacement per revolution can be varied.
Volumetric Displacement: The volume for one revolution.
32BDR
© 2013 HYDRO-GEAR
Printed in U.S.A.
Rev. P1
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