General Description ..................................................................................................................................... 1
External Features BDP-10A ......................................................................................................................... 2
External Features BDP-16A ......................................................................................................................... 3
External Features BDP-21L ......................................................................................................................... 4
Personal Safety ........................................................................................................................................... 9
Work Area Safety ........................................................................................................................................ 9
Tools and Torques ................................................................................................................................. 15,16
Input Shaft Seal BDP-10A/16A/21L ............................................................................................................ 17
Trunnion Arm Seal BDP-10A/16A/21L ........................................................................................................ 18
Parts List ...................................................................................................................... 35-40
Glossary of Terms ....................................................................................................... 41-42
FOREWORD
Headquartered in Sullivan, Illinois, Hydro-Gear is
a world leader in the design, manufacture, and
service of quality hydrostatic transaxles 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 the
Hydro-Gear 10cc Bantam Duty Pump (BDP10A), 16cc Bantam Duty Pump (BDP-16A) and
21cc Bantam Duty Pump (BDP-21L).
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 good shop practice, that your
service area be equipped with proper tools and
the mechanics to be supplied with the latest
information available. All repair procedures illustrated in this guide are suggested, but
preferred methods of repair.
Some repair procedures require that the BDP 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 the ESA (Engine Service
Association) (610) 363-3844 or their Hydro-Gear
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.
BDP-10A/16A/21L i
SECTION 1. DESCRIPTION AND OPERATION
INTRODUCTION
The purpose of this manual is to provide information useful in servicing the Hydro-Gear Bantam Duty Pumps (BDP’s). This manual includes
the BDP’s general descriptions, hydraulic schematics, technical specifications, servicing and
troubleshooting procedures for BDP models
10A, 16A and 21L.
The BDP’s 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 BDP’s will need to be thoroughly cleaned
before beginning most procedures.
The models BDP -10A, 16A and 21L differ from
the BDP model 10L. The physical distinction in
appearance of the BDP-10A, 16A and 21L is
signified by the design of an aluminum end cap.
This end cap improves versatility in the application of these products.
GENERAL DESCRIPTION
The BDP’s can be combined with wheel motors
and other remotely located units. These pumps
provide an infinitely variable speed range between zero and full displacement in both forward
and reverse modes of operation.
The BDP-10A, 16A and 21L are of the axial piston design, utilizing spherical nosed pistons. A
compression spring, located inside each piston,
holds the nose of the piston against a thrust bearing race.
The variable displacement pump features a
cradle swashplate with a direct-proportional displacement control. Reversing the direction of
the angle of the swashplate reverses the flow of
oil from the pump and thus reverses the direction of motor output rotation.
Movement of the directional control shaft produces a proportional swashplate movement and
a change in pump flow and/or direction.
A fixed displacement gerotor charge pump is provided in the BDP units. Oil from the external reservoir and filter is pumped into the closed loop by
a charge pump. Fluid not required to replenish
the closed loop flows either into the pump housing through a cooling orifice, or back to the charge
pump inlet through the charge pressure relief
valve.
Check valves are included in the pump end cap
to control the makeup oil flow for the system. The
size and type of check valve can play an important role on the system pressure, response, and
amount of heat generated, due to the recirculation of makeup oil flow. Additionally, some BDP’s
may be equipped with System Check Reliefs
(SCR’s). SCR’s are factory preset pressure regulating check valves.
In some applications of the BDP’s, it is desirable
to move the machine for short distances at low
speeds without operating the engine. An increase
in resistance will occur with movement at higher
speeds. A screw type bypass valve is utilized in
the pumps to permit movement of the machine.
The bypass valve is fully opened when unscrewed
two (2) turns maximum. The bypass valve allows
oil to be routed from one side of the pump/motor
circuit to the other, thus allowing the motor to turn
with minimal resistance. The bypass valve must
be fully closed during normal operation.
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.
Additionally, some BDP’s may be equipped with
an Auxiliary Pump. The Auxiliary incorporates
the principles of the charge gerotor assembly and
provides the capability of an external auxiliary flow
for an alternate hydraulic circuit to operate accessories without loss of drive.
1
BDP-10A/16A/21L
EXTERNAL FEATURES BDP-10A
SAE "A" PAD
FLANGE STYLE
TRUNNION ARM
STANDARD CHECK VALVE
STANDARD CHECK
OR SHOCK VALVE
VALVE OR SCR
CASE DRAIN
OPTION
"A" and "B"
PORTS
CHARGE
COVER
BYPASS VALVE
CHARGE
PRESSURE
DIAGNOSTIC
PORT
STANDARD CHECK VALVE
STANDARD CHECK
OR SHOCK VALVE
VALVE OR SCR
INLET
CASE DRAIN
OPTION
INPUT SHAFT
TRUNNION ARM
BDP-10A/16A/21L
Figure 1. BDP-10A With Standard Charge Pump
2
EXTERNAL FEATURES BDP-16A
BYPASS
VALV E
SAE “A” PAD
FLANGE STYLE
TRUNNION ARM
INPUT SHAFT
CHARGE PRESSURE
DIAGNOSTIC PORT
“A” and “B” PORTS
SYSTEM CHECK VALVE
OR SHOCK VALVE
CASE DRAIN
BYPASS VALVE
CHARGE
COVER
INLET
SYSTEM CHECK VALVE
OR SHOCK VALVE
CASE DRAIN
3
Figure 2. BDP-16A With Standard Charge Pump
BDP-10A/16A/21L
EXTERNAL FEATURES BDP-21L
T
INPUT SHAFT
SAE "B" PAD
FLANGE STYLE
R
U
N
N
I
O
N
R
A
"A" and "B"
PORTS
M
CHARGE
PRESSURE
DIAGNOSTIC
PORT
BYPASS VALVE
STANDARD CHECK VALVE
STANDARD CHECK
OR SHOCK VALVE
VALVE OR SCR
Figure 3. BDP-21L With Standard Charge Pump
INLET
CHARGE
COVER
CASE DRAIN
STANDARD CHECK VALVE
STANDARD CHECK
OR SHOCK VALVE
VALVE OR SCR
BDP-10A/16A/21L
4
HYDRAULIC SCHEMATIC
SYSTEM CHECK & RELIEF VALVE OPTIONS:
1) NO SCR, NO BLEED
2) NO SCR, .024” BLEED
3) NO SCR, .031” BLEED
4) NO SCR, .044” BLEED
5) 3000 PSI SCR, NO BLEED (BDP-10A/16A)
3000 PSI SHOCK, NO BLEED (BDP-10A/16A)
6) 3000 PSI SHOCK, .024” BLEED (BDP-10A/16A)
7) 3000 PSI SCR, .031” BLEED (BDP-10A/16A)
3000 PSI SHOCK, .031” BLEED (BDP-10A/16A)
8) 3000 PSI SHOCK, .044” BLEED (BDP-10A/16A)
PORT A
PORT B
Figure 4. BDP-10A/16A With Standard Charge Pump Hydraulic Schematic
AUXILIARY DISCHARGE
AUXILIARY RETURN
CHARGE PUMP INLET
CHARGE DIAGNOSTIC
BYPASS VALVE BLEED OPTIONS:
1) NO BLEED ORIFICE
2) .031” BLEED ORIFICE
3) .043” BLEED ORIFICE (BDP-10A/16A)
SYSTEM CHECK & RELIEF VALVE OPTIONS:
1) NO SCR, NO BLEED
2) NO SCR, .024” BLEED
3) NO SCR, .031” BLEED
4) NO SCR, .044” BLEED
5) 3000 PSI SCR, NO BLEED (BDP-10A/16A)
3000 PSI SHOCK, NO BLEED (BDP-10A/16A)
6) 3000 PSI SHOCK, .024” BLEED (BDP-10A/16A)
7) 3000 PSI SCR, .031” BLEED (BDP-10A/16A)
3000 PSI SHOCK, .031” BLEED (BDP-10A/16A)
8) 3000 PSI SHOCK, .044” BLEED (BDP-10A/16A)
PORT A
5
PORT B
CHARGE PUMP INLET
CHARGE DIAGNOSTIC
BYPASS VALVE BLEED OPTIONS:
1) NO BLEED ORIFICE
2) .031” BLEED ORIFICE
3) .043” BLEED ORIFICE (BDP-10A/16A)
Figure 5. BDP-10A/16A With Auxiliary Charge Pump Hydraulic Schematic
BDP-10A/16A/21L
HYDRAULIC SCHEMATIC
SCR, NO BLEED ORIFICE
6) SCR, .031” BLEED ORIFICE
7) SHOCK, NO BLEED ORIFICE
8) SHOCK, .024” BLEED ORIFICE
3) .043” BLEED ORIFICE
9) SHOCK, .031” BLEED ORIFICE
10) SHOCK, .044” BLEED ORIFICE
Figure 6. BDP-21L With Standard Charge Pump Hydraulic Schematic
6) SCR, .031” BLEED ORIFICE
7) SHOCK, NO BLEED ORIFICE
8) SHOCK, .024” BLEED ORIFICE
9) SHOCK, .031” BLEED ORIFICE
10) SHOCK, .044” BLEED ORIFICE
SCR, NO BLEED ORIFICE
BDP-10A/16A/21L
3) .043” BLEED ORIFICE
Figure 7. BDP-21L With Auxiliary Charge Pump Hydraulic Schematic
6
GRAPHICAL SCHEMATIC
Figure 8. BDP-10A,16A and 21L Standard Charge Pump Graphical Schematic
Figures 4-7 represent hydraulic schematics of
the standard charge and auxiliary charge pump.
Figure 8 provides a graphical 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 or direct drive gear box.
The oil is drawn through an external filter that prevents contaminants within the reservoir from entering into the charge pump gerotor.
The charge pump supplies fluid to keep the
closed loop pressurized, preventing cavitation
and providing cooling oil flow for the system.
The charge relief valve is used to maintain charge
at a predetermined pressure.
Output of the system oil flow is controlled by the
direction and amount that the swashplate is
angled. As the pump pistons compress, they
force oil into one of two passageways (“A” or “B”)
in the system hydraulic circuit. Oil is supplied ex-
ternally under pressure to an external load, (e.g.,
a vehicle wheel motor). 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 wheel motor. Reversing the angle
of the swashplate will reverse the direction of the
oil flow. During the operation of the pump, fluid
is “lost” from the hydraulic loop through leak paths
designed into the product for lubrication purposes
(around pistons, under the rotating cylinder
block, etc.). This “lost” fluid returns to the reservoir through the case drain. This fluid must be
made up in the loop. The charge pump makes
up this fluid loss.
The makeup flow is controlled (or directed) by
the system check valves. The check valves are
used to direct makeup fluid into the low pressure
side of the closed loop. Each check valve will
either be held open or closed, depending upon
the direction of the vehicle operation: Closed in
a pressurized system passage, open in a low
pressure, “charged” system passage.
7
BDP-10A/16A/21L
TECHNICAL SPECIFICATIONS
BDP-10ABDP-16ABDP-21L
3
Displacement
Input Speeds
Maximum:
Minimum:
System Operating Pressure
Intermi tte nt:
Continuous:
0.623 in
7.6 gpm@3000 rpm (1000 psi)
/ rev (10.2 cc / rev)
3600 rpm
1800 rpm
2100 psi (145 bar)
1000 psi (70 bar)
0.97 in3 / rev (16 cc / rev)
12 gpm@3000 rpm (1000 psi)
3600 rpm
1800 rpm
2500 psi (172 bar)
1250 psi (86 bar)
1.33 in3 / rev. (21.8 cc / rev)
16.4 gpm@3000 rpm (1000 psi)
3600 rpm
1800 rpm
2500 psi (172 bar)
1250 psi (86 bar)
Oil Temperature
Maximum Intermittent:
Normal Operating Range:
Fluid Viscosity Limits
o
F (110o C) Opti mum:
@230
o
F (110o C) Minimum:
@230
Weight
-10
o
F (110o C)
230
o
to 200o F (23o C to 93o C)
70 SUS (13 cST)
55 SUS (9.0 cST)
8 lbs (3.6 kg)12 lbs (5.4 kg)14 lbs (6.3 kg)
-10
o
230
o
F (110o C)
to 200o F (23o C to 93o C)
70 SUS (13 cST)
55 SUS (9.0 cST)
230
o
to 200o F (23o C to 93o C)
-10
70 SUS (13 cST)
55 SUS (9.0 cST)
o
F (110o C)
Table 1. BDP-10A/16A/21L Technical Specifications
PRODUCT IDENTIFICATION
The label in Figure 9. can be located on the pump housing. It identifies the model and configuration of the BDP.
H Y D R O - G E A R
SULLIVAN, IL. U.S.A.
OEM Model/
Hydro-Gear
Number
(Julian - day of year)
BDP-10A/16A/21L
Year Built
Date
I IIII III IIII II II
BDP- 10A - 300 or (BDP - 21L - 102)
I II IIII IIII III III I II IIII
0
131 P1 476
(unique number for that model - for that day)
Type of Product and Build Information
Figure 9. BDP Configuration Label
Made in U.S.A.
Serial Number
8
SECTION 2. 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 BDP’s. 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
BDP-10A, 16A or 21L, fully read and understand the safety precautions described in this section.
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.
PERSONAL SAFETY
Certain safety precautions must be observed
while servicing or repairing the BDP-10A, 16A
or 21L. This section addresses some of these
precautions but must not be considered an allinclusive source on safety information. This section is to be used in conjunction with all other
safety material which may apply, such as:
Other manuals pertaining to this machine
Local and shop safety rules and codes
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.
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.
9
BDP-10A/16A/21L
SECTION 3. TROUBLESHOOTING
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!
In many cases problems with the BDP-10A, 16A
and 21L are not related to a defective pump 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 Section 3. before assuming the pump is malfunctioning. Table 2. below provides a troubleshooting
Follow all safety procedures outlined in
the vehicle owner’s manual!
Table 2. BDP 10A, 16A and 21L Troubleshooting Checklist
check list to help determine the cause of operational problems.
Possible CauseCorrective Action
VEHICLE DOES NOT DRIVE/TRACK STRAIGHT
Vehicle tires improperly inflatedRefer to vehicle manufacturer suggested pressure
Control linkage bent, loose or out of adjustmentRepair, adjust or replace vehicle linkage
Bypass looseTighten bypass per page 11
Inlet leakCheck all externals to BDP inlet
UNIT IS NOISY
Excessive input speedAdjust input speed above 1800 rpm and below 3600 rpm
Oil level low or contaminated oilFill to proper level or change oil
Excessive loadingReduce vehicle load
Air trapped in hydraulic systemPurge hydraulic system per page 12
Bypass looseTighten bypass per page 11
Inlet leak, line or filter partially blocked or damagedCheck all externals to BDP inlet
UNIT HAS NO/ LOW POWER
Engine speed lowAdjust to correct setting
Control linkage bent, loose or out of adjustmentRepair or replace vehicle linkage
Drive belt slipping or pulley damagedRepair or replace drive belt or pulley
Oil level low or contaminated oilFill to proper level or change oil per page 11
Excessive loadingReduce vehicle load
Bypass looseTighten bypass per page 11
Air trapped in hydraulic systemPurge hydraulic system per page 12
Inlet leakCheck all externals to BDP inlet
Inlet filter cloggedReplace filter per page 12
Suspected internal damageCheck per page 9
UNIT OPERATING HOT
Debris buildupRemove debris
Cooling fan or heat exchanger damagedRepair or replace cooling fan or heat exchanger
Oil level low or contaminated oilFill to proper level or change oil per page 11
Excessive loadingReduce vehicle load
Air trapped in hydraulic systemPurge hydraulic system per page 12
Inlet leakCheck all externals to BDP inlet
BDP LEAKS OIL
Damaged seals or gasketsRemove debris, replace seals
Air trapped in hydraulic systemPurge hydraulic system per page 12
BDP-10A/16A/21L
10
BDP FLOW TEST KIT INSTRUCTIONSBLN-51334 FEBRUARY 2003
(This Instruction Sheet supersedes all previous flow testing instructions)
Description: BDP Flow Test Kit (Part Number 70661)
(Part Number 70661 Supersedes Part Numbers 70511 and BB-76810)
Purpose:
motor and determine if the BDP is faulty. The following information can be used to install and test the BDP by
simulating a wheel motor load.
The design purpose of the BDP Flow Test Kit is to allow the dealer to isolate the BDP from the wheel
WARNING
Certain procedures require the vehicle engine
to be operated and the vehicle to be raised off of
the ground. To prevent possible injury to the
servicing technician and/or bystanders, insure
the vehicle is properly secured.
Do not attempt any adjustments with the engine
running. Use extreme caution while working in
or around all vehicle linkage! High temperatures
can be generated. Follow all safety procedures
outlined in the vehicle owner’s manual!
WARNING
INSTALLATION AND TESTING PROCEDURES:
1. Disconnect the system hoses at the wheel motor, or system hoses from the BDP and connect the BDP Flow
Test Kit. (Special care should be taken to prevent contamination debris from entering pump or wheel motor
system ports).
Note: Using the Bi-Directional Flow Test Kit, determination of directional flow is not necessary. The flow meter
may be connected in either direction into the forward and reverse high pressure system lines.
CAUTION: Ensure all fittings and hoses are attached securely. This test is being completed on the
vehicle’s high pressure system lines. Failure to perform this properly could result in bodily injury.
TESTING PROCEDURES:
1. Raise the drive tires off the ground. Block the remaining tires on the ground to prevent accidental vehicle
movement.
2. Open the restriction valve all the way.
3. Make certain all external BDP directional control stops are removed or backed off on the vehicle linkage to
obtain full pump directional control arm travel.
4. Start the engine and engage the drive pulley if necessary.
5. Bring the engine to maximum operating speed.
(This should not exceed 3600 rpm input speed on the BDP-10A/10L)
(This should not exceed 3400 rpm input speed on the BDP-16A)
(This should not exceed 2800 rpm input speed when testing the BDP-21L)
Engine speed adjustment may be necessary to obtain 2800 rpm.
CAUTION: Damage to the flow meter and/or re-calibration may result from testing the BDP-21L at
input speeds that exceed 2800 rpm.
6. With the directional control lever (on the vehicle) for the pump being tested, move the control arm in full
forward motion. (It may be necessary to lock the control arm into full forward position to prevent false
readings).
7. Operate without any load for approximately 30 seconds to 1 minute, this allows the system oil temperature to
rise.
11
BDP-10A/16A/21L
Note: Raising the system oil temperature will make a difference in the readings you receive. It has been
determined that to complete this test accurately, the oil temperature must be near system operating temperatures.
Suggested temperature range 160°- 210°F (71.1° - 98.9°C)
8. On the BDP-10A/10L, BDP-16A and BDP-21L tighten the restriction valve until you read 300 psi (21 bar).
Record the flow reading from the Bi-Directional Flow Meter.
9. Increase the pressure to 1100 PSI (76 bar) for all models (BDP-10A/10L, BDP-16A and BDP -21L).
Record the flow reading from the Bi-Directional Flow Meter.
10. The acceptable gpm “flow droop” or (difference) is:
Subtract the 1st reading from the 2nd.
(In this example, 4 gpm difference would
indicate a defective pump).
BDP-10A/16A/21L
12
SECTION 4. 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 BDP should
include the following:
1. Check the vehicle operator’s manual for
the recommended load ratings. Insure
the current application does not exceed
load rating.
2. Check fluid level in reservoir in accordance
with vehicle manufacturer’s recommendations.
NOTE: After oil has been drained and
maintenance has been performed, clean
oil should be poured directly into the
pump inlet and high pressure ports prior
to plumbing reconnection and start-up.
3. Inspect the vehicle drive belt, idler pulley(s),
and idler spring(s). Insure that belt slippage
is not causing low input rpm to the pump.
4. Inspect all external plumbing for possible
leaks or loose fittings. An air leak may be
difficult to detect on the “suction side” or inlet
line to the pump. See purging procedures
page 12.
5. Insure correct inlet filter(s) has been installed
in accordance with the vehicle manufacturer.
6. Insure the reservoir is free of contaminants
and is properly vented.
7. Inspect the BDP cooling fan (if applicable)
for broken or distorted blades and remove
any obstructions (grass clippings, leaves or
dirt). Inspect oil cooler (if applicable) for damaged fins and debris.
8. Inspect the vehicle control linkage to the directional control arm on the BDP. Also, insure the control arm is securely fastened to
the trunnion arm.
9. Inspect the bypass on the BDP to insure it is
properly engaged for operation. If the bypass
is not fully engaged (rotated fully clockwise)
it will not function properly. For vehicle movement, the bypass may be backed out (2) turns
maximum. This is only recommended for
movement of short distances at low speeds.
WARNING
Loosening the bypass will result in loss
of hydraulic braking capability.
SERVICE AND MAINTENANCE
PROCEDURES
NOTE: Damage to BDP’s may result from
external or internal contamination: Heat
from excess debris or lack of lubrication
and over-pressurization of the product.
Follow guidelines established in this
manual and the vehicle manufacturer’s
recommendations.
All the service procedures presented on the following pages can be performed while the BDP
is mounted on the vehicle. Any servicing beyond
those given must be performed after the unit has
been removed from the vehicle.
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
55 SUS (9.0 cSt) at 230° F (110° C) maximum
operating temperature and an API classification
of SJ/ CD is allowed. Refer to the vehicle manufacturer for recommended oil.
13
BDP-10A/16A/21L
FLUID VOLUME AND LEVEL
Certain situations may require additional fluid to
be added or even replaced. Refer to the vehicle
manufacturer’s recommendations for the proper
fill location and level. After maintenance or oil
change, follow purging procedures below and recheck the fluid level once the unit has been operated for approximately 1 minute.
FLUID CHANGE
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. Refer to purging procedures below.
FILTERS
An inlet filter is required to insure that only clean
fluid enters the system. Refer to the vehicle manufacture for approved filter replacement.
PURGING PROCEDURES
Due to the effects air has on efficiency in hydrostatic drive applications, it is critical that air is
purged from the system.
These purge procedures should be implemented anytime a hydrostatic system has been
opened to facilitate maintenance or any additional oil has been added to the system.
Air creates inefficiency because it has compression and expansion rates that are higher than
that of oil.
Entrained air in the oil may cause the following
symptoms:
1. Noisy operation
2. Lack of power or drive after short-term operation
3. High operation temperature and excessive
expansion of oil.
Before starting, make sure the reservoir is at the
proper oil level. If it is not, fill to the vehicle
manufacturer’s specifications.
The following procedures should be performed
with the vehicle drive wheels off the ground, then
repeated under normal operating conditions.
WARNING
POTENTIAL FOR SERIOUS INJURY
Certain procedures require the vehicle
engine to be operated and the vehicle to
be raised off of the ground. To prevent
possible injury to the servicing technician and/or bystanders, insure the vehicle is properly secured.
1. With the bypass valve open and the engine
running, slowly move the directional control
in both forward and reverse directions (5 to 6
times), as air is purged from the unit, the oil
level will drop.
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 engine.
3. It may be necessary to repeat Steps 1 and 2
until all the air is completely purged from the
system. When the BDP’s move forward and
reverse at normal speed purging is complete.
Cleanliness is a key factor in the successful repair of BDP’s. 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 areas and open cavities from damage and foreign material.
Upon removal, all seals, O-rings, and gaskets
should be replaced. During installation, lightly
lubricate all seals, O-rings, gaskets with clean
petroleum jelly prior to assembly. Also protect
the inner diameter of seals by covering the shaft
machined features with plastic wrap or equivalent.
BDP-10A/16A/21L
14
SECTION 5. REPAIR
HOW TO USE THIS MANUAL
Each assembly is provided with an exploded
view showing the parts involved. The item
reference numbers in each illustration are
for assembly instructions only. See pages
35-40 for part names and descriptions. A
complete exploded view and item list of the pump
is provided at the end of this section.
GENERAL INSTRUCTIONS
Cleanliness is a primary means of assuring
satisfactory life on repaired pumps. 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.
Lip type seals (shaft seals) are used on the input
shaft and directional control shaft of the
BDP-10A, 16A and 21L. These seals can be
replaced without major disassembly of the unit.
However, replacement of these seals generally
requires removal of the pump from the machine.
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 the
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
listed in BLN-50937 (microfiche) or BLN-51427
(CD).
TOOLS AND TORQUES
Table 3. Required Tools
Miscellaneous
BDP-10A/16A/21L Service & Repair Manual
Torque Wrench
Scribe, Paint Pen, or Marker
Seal Hook with a Magnet
Flat Blade Screw Driver
REMOVAL, INSPECTION AND/OR REPLACEMENT OF INPUT SHAFT
SEAL BDP-10A
REMOVAL, INSPECTION AND/OR REPLACEMENT OF INPUT SHAFT
SEAL BDP-16A/21L
Refer to Figure 10.
Disassembly BDP-10A
1. Remove retaining ring (22) from housing.
2. Remove lip seal (20). Care must be taken to
prevent damage to the housing bore, shaft sealing surface, or bearing. Once removed, the seal
is not reusable.
Inspection BDP-10A
1. With seal removed inspect the spacer (21),
input shaft bearing (19) and housing (1) bore for
damage, corrosion or wear.
Assembly BDP-10A
1. Lubricate the new lip seal (20) with petroleum
jelly.
2. Wrap the input shaft (18) with plastic wrap to
prevent damage to the inner surface of the lip
seal (20).
Refer to Figure 11.
Disassembly BDP-16A/21L
1. Remove retaining ring (3) from housing (15).
2. Remove lip seal (6). Care must be taken to
prevent damage to the housing bore, shaft, sealing surface, or bearing. Once removed the seal
is not reusable.
Inspection BDP-16A/21L
1. With the lip seal (6) removed, inspect the
spacer (4) the shaft bearing (5) and housing (15)
bore.
Assembly BDP-16A/21L
1. Lubricate the new lip seal (6) with petroleum
jelly.
2. Wrap the input shaft (1) with plastic wrap to
prevent damage to the inner surface of the lip
seal (6).
3. Slide seal (20) over shaft (18) so that lettering on the seal faces out.
4. Press the lip seal (20) into the housing bore.
Insure the lip seal (20), shaft (18) or housing (1)
bore does not become damaged.
5. Install the retaining ring (22) into the housing
(1) bore groove.
22
20
21
19
18
1
3. Slide the seal (6) over shaft (1) so that letter-
ing on the seal (6) faces out.
4. Press the lip seal (6) into the housing (15)
bore. Insure seal (6), shaft (1) or housing (15)
bore does not become damaged.
5. Install the retaining ring (3) into the housing
(15) bore groove.
3
6
5
15
1
4
17
Figure 10. BDP-10A
Figure 11. BDP-16A/21L
BDP-10A/16A/21L
REMOVAL, INSPECTION AND/OR REPLACEMENT OF TRUNNION ARM
(CONTROL ARM) SEAL BDP-10A/16A
REMOVAL, INSPECTION AND/OR REPLACEMENT OF TRUNNION ARM
(CONTROL ARM) SEAL BDP-21L
Refer to figure 12.
Disassembly BDP-10A/16A
1. Remove the retainer and lip seal (49/12) from
the housing (1/15). Care must be taken to prevent damage to the housing trunnion bore, trunnion arm (37/13) and sealing surface.
Once re-
moved the retainer and lip seal is not reusable.
Inspection BDP-10A/16A
1. With the lip seal (49/12) removed, inspect the
area for corrosion and wear. Inspect the trunnion bore area sealing surface for damage or
wear.
Assembly BDP-10A/16A
1. Lubricate the new lip seal (49/12) with petroleum jelly.
2. Wrap the trunnion arm (37/13) with plastic
wrap to prevent damage to the inner surface of
the lip seal (49/12).
3. Slide the lip seal (49/12) over the trunnion arm
(37/13) so that the lettering on the seal (49/12) faces
out.
Refer to figure 13.
Disassembly BDP-21L
1. Remove the retainer (10) and lip seal (2).
Care must be taken to prevent damage to the
housing trunnion bore, trunnion arm (13) and
sealing surface. Once removed lip seal (12) is
not reusable.
Inspection BDP-21L
1. With the lip seal (12) removed, inspect the
area for corrosion and wear. Inspect the trunnion bore area sealing surface for damage or
wear.
Assembly BDP-21L
1. Lubricate the new lip seal (12) with petroleum
jelly.
2. Wrap the trunnion arm (13) with plastic wrap
to prevent damage to the inner surface of the lip
seal (12).
3. Slide the lip seal (12) over the trunnion arm
(13) so that lettering on the seal (13) faces out.
4. Press the lip seal (49/12) into the housing
bore (1/15). Insure the seal (49/12), trunnion arm
(37/13), and housing bore does not become
damaged.
5. Install the retainer from (49/12) over the trunnion arm (37/13) on top of the lip seal from (49/
12). Press into the trunnion seal bore in the housing until it mates against the trunnion seal.
1/15
37/13
49/12
Figure 12. BDP-10A/16A
4. Press the lip seal (12) into the housing bore
(15). Insure the seal (12), trunnion arm (13), and
housing bore does not become damaged.
5. Install the retainer (10) over the trunnion arm
(13) on top of the lip seal (12). Press into the
trunnion seal bore in the housing (15) bore ring
groove.
15
10
12
13
Figure 13. BDP-21L
BDP-10A/16A/21L
18
REMOVAL, INSPECTION AND/OR REPLACEMENT OF CHECK VALVES
BDP-10A/16A
REMOVAL, INSPECTION AND/OR REPLACEMENT OF CHECK VALVES
BDP-21L
Refer to Figure 14.
Disassembly BDP-10A/16A
Perform disassembly, inspection and assembly
on check valves one side at a time. Some units
vary in “A” side to “B” side check configuration.
1. Remove the check valve (42) with 1/4” allen
wrench.
2. Remove the valve spring and poppet from
the BDP end cap (2/25).
Inspection BDP-10A/16A
1. Inspect the poppets and mating seats in the
end cap (2/25) for damage or foreign material.
Assembly BDP-10A/16A
1. Lay the BDP on its side, so the check plug
port is horizontal.
Refer to Figure 15.
Disassembly BDP-21L
Perform disassembly, inspection and assembly
on check valves one side at a time. Some units
vary in “A” side to “B” side check configuration.
1. Remove the check valve (42) with 1/4” allen
wrench.
2. Remove the valve spring and poppet from
the BDP end cap (25).
Inspection BDP-21L
1. Inspect the poppet and mating seats in the
end cap (25) for damage or foreign material.
Assembly BDP-21L
1. Lay the BDP on its side, so the check plug
port is horizontal.
2. Insert the check plug, spring and poppet (42)
as one assembly into the check plug port.
Tighten, reference Tables 4 & 5, page 16, for
torque values.
Repeat disassembly, inspection and assembly
for the opposite port side.
42A
(PORT "A"
SIDE)
2/25
42B
(PORT "B"
SIDE)
Figure 14. BDP-10A/16A
2. Insert the check plug, spring and poppet (42)
as one assembly into the check plug port.
Tighten, reference Table 6, page 16, for torque
values.
Repeat disassembly, inspection and assembly
for the opposite port side.
42B
42A
25
Figure 15. BDP-21L
19
BDP-10A/16A/21L
REMOVAL, INSPECTION AND/OR REPLACEMENT OF SYSTEM CHECK
RELIEFS (SCR’s) OR SHOCK
VALVES BDP-10A/16A
REMOVAL, INSPECTION AND/OR REPLACEMENT OF SYSTEM CHECK
RELIEFS (SCR’s) OR SHOCK
VALVES BDP-21L
Refer to Figure 16.
Disassembly BDP-10A/16A
Perform disassembly, inspection and assembly
on SCR/shock valve one side at a time. Some
units vary in “A” side to “B” side configuration.
1. Remove the SCR (42) with a 7/8” wrench or
the shock valve (42) with an 11/16” wrench.
2. Remove the check relief/shock valve spring
and the check relief/shock valve from the BDP
end cap (2/25).
Inspection BDP-10A/16A
1. Inspect the check relief or shock valve (42)
and mating seat in the end cap (2/25) for damage or foreign material.
Assembly BDP-10A/16A
1. Lay the BDP on its side, so the check plug
port is horizontal.
Refer to Figure 17.
Disassembly BDP-21L
Perform disassembly, inspection and assembly
on SCR/shock valve one side at a time. Some
units vary in “A” side to “B” side configuration.
1. Remove the SCR (42) with a 7/8” wrench or
the shock valve (42) with an 11/16” wrench.
2. Remove the check relief/shock valve spring
and the check relief/shock valve from the BDP
end cap (25).
Inspection BDP-21L
1. Inspect the check relief or shock valve(42)
and mating seat in the end cap (25) for damage
or foreign material.
Assembly BDP-21L
1. Lay the BDP on its side, so the check plug
port is horizontal.
2. Insert the system check relief spring and
check relief or shock valve spring and shock
valve as one assembly into the check plug port.
Tighten to the correct torque value. See page 16.
Repeat disassembly, inspection and assembly
for the opposite port side.
42A
42B
2/25
Figure 16. BDP-10A/16A
2. Insert the system check relief spring and
check relief or shock valve spring and shock
valve as one assembly into the check plug port.
Tighten, reference Table 6, page 16, for torque
values.
Repeat disassembly, inspection and assembly
for the opposite port side.
42B
42A
25
Figure 17. BDP-21L
BDP-10A/16A/21L
20
REMOVAL, INSPECTION AND/OR REPLACEMENT OF THE BYPASS BDP10A/16A
REMOVAL, INSPECTION AND/OR REPLACEMENT OF THE BYPASS BDP21L
Refer to Figure 18.
Disassembly BDP-10A/16A
1. Loosen the bypass valve (15/50) using a 5/8”
wrench.
2. Remove the bypass (15/50) from the BDP
end cap (2/25).
Inspection BDP-10A/16A
1. Inspect the bypass O-rings and mating seats
in the end cap (2/25) for damage or foreign material.
2. If damaged or worn replace bypass (15/50).
Assembly BDP-10A/16A
1. Lay the BDP on its side, so the bypass port
is horizontal.
2. Insert the bypass (15/50) into the bypass
port on the end cap (2/25). Tighten to the proper
torque value. See page 16.
Refer to Figure 19.
Disassembly BDP-21L
1. Loosen the bypass valve (50) using a 5/8”
wrench.
2. Remove the bypass (50) from the BDP end
cap (25).
Inspection BDP-21L
1. Inspect the bypass O-rings and mating seats
in the end cap (25) for damage or foreign material.
2. If damaged or worn replace bypass (50).
Assembly BDP-21L
1. Lay the BDP on its side, so the bypass port
is horizontal.
2. Insert the bypass (50) into the bypass port
on the end cap (25). Tighten, reference Table 6,
page 16, torque values.
2/25
15/50
Figure 18. BDP-10A/16A
50
25
Figure 19. BDP-21L
21
BDP-10A/16A/21L
REMOVAL, INSPECTION AND
ASSEMBLY OF THE STANDARD
CHARGE PUMP BDP-10A
Refer to Figure 20.
Disassembly BDP-10A
1. Prior to removal of the charge cover, place a
mark on the charge cover and end cap for realignment.
2. Using a 5 mm allen wrench, loosen the charge
cover bolts (10) from the BDP end cap (2). While
holding the charge cover in place, remove the
charge cover bolts (10).
3. Remove the charge cover, O-ring, gerotor
items (6), charge spring and charge ball (44).
Inspection BDP-10A
1. Inspect the charge cover O-ring and running
surfaces for damage. Inspect the spring , check
ball (44), and mating seat in the end cap (2) for
damage or foreign material.
Assembly BDP-10A
1. Lay the BDP (input shaft down), so the end
cap (2) is horizontal. Place the charge ball (44)
in the end cap (2) charge pocket so it mates to
the end cap (2) charge ball seat. Place the
charge spring, also identified as item (44), on
top of the charge ball.
2. Insert the inner gerotor over input shaft (18).
3. Align the outer gerotor to fit over the inner
gerotor.
4. Insert the O-ring into the charge cover.
5. Position the charge cover and O-ring with the
aligning mark on the end cap. Place the charge
cover and O-ring as one piece over the charge
spring and gerotor assembly. Insure the spring
fits into the charge cover spring retaining groove.
6. Align and insert the allen screws (6) into the
end cap (2). Tighten, reference Table 4, page
16, torque values.
Note: If end cap (2) is to be removed, delay charge components reassembly.
Partial View
6
10
44
18
2
BDP-10A/16A/21L
Figure 20. BDP-10A
22
REMOVAL, INSPECTION AND ASSEMBLY OF THE STANDARD
CHARGE PUMP BDP-16A/21L
Refer to Figure 21.
Disassembly BDP-16A/21L
1. Prior to removal of the charge cover, place a
mark on the charge cover and end cap for realignment.
Assembly BDP-16A/21L
1. Lay the BDP (input shaft down), so the end
cap is horizontal. Place the charge ball in the
end cap (25) charge pocket so it mates to the
end cap (25) charge ball seat. Place the charge
spring on top of the charge ball.
2. Insert the inner gerotor over input shaft (1).
3. Align the outer gerotor to fit over the inner
gerotor.
2. Using a 1/2” wrench loosen the charge cover
bolts from the BDP end cap (25). While holding
the charge cover in place, remove the charge
cover bolts (56).
3. Remove the charge cover, O-ring, gerotor
items (40), charge spring and charge ball (44).
Inspection BDP-16A/21L
1. Inspect the charge cover O-ring and running
surfaces for damage. Inspect the spring , check
ball (44), and mating seat in the end cap (25) for
damage or foreign material.
2. If damaged or worn, replace O-ring and
gerotor assembly (40), charge spring and charge
ball (44) and end cap (25).
Note: If end cap (25) is to be removed,
delay charge components reassembly.
4. Insert the O-ring into the charge cover.
5. Position the charge cover and O-ring with the
aligning mark on the end cap (25). Place the
charge cover and O-ring as one piece over the
charge spring and gerotor assembly. Insure the
spring fits into the charge cover spring retaining
groove.
6. Align and insert the cap screws (56) into the
charge cover. While holding the charge cover in
place tighten the cap screws (56) per Tables 5
and 6, page 16.
23
44
Partial View
4x 58
40
56
56
BDP-16A
1
25
Figure 21. BDP-16A/21L
40
56 x2
1
25
44
58 x4
BDP-21L
BDP-10A/16A/21L
REMOVAL, INSPECTION AND ASSEMBLY OF THE END CAP AND
VALVE PLATE BDP-10A
Refer to Figure 22.
Disassembly BDP-10A
1. Using a 10 mm wrench, loosen the end cap
bolts (4) evenly.
2. Keeping the end cap (2) held in place, remove the four end cap bolts (4).
3. Slowly remove the end cap (2).
4. Remove the valve plate (31).
5. Remove housing alignment pins (3).
6. Remove housing gasket (5).
Inspection BDP-10A
1. Inspect the end cap (2) body for damage,
nicks or unusual wear patterns. Replace if necessary.
2. Inspect the running surface (side that contacts the cylinder block) of the valve plate (31).
The running surface may show evidence of
minor abrasive rings.
This is normal. Grooving in the plate, or material
transfer that is evident when the surface is
checked by dragging a fingernail across it, would
be cause for replacement of the valve plate.
3. Inspect and replace alignment pins (3) if bent
or distorted.
4. Replace the housing gasket (5) with a new
gasket before reassembly.
Assembly BDP-10A
1. Install housing gasket (5) into housing gasket
seat in housing (1).
2. Install alignment pins (3) into housing (1).
3. Lubricate the valve plate prior to installation.
Install valve plate (31) so the stamped letters “CL”
on the valve plate are facing up toward the
endcap.
4. Install end cap (2). Before installing the four
end cap bolts (4), push down on end cap (2)
verifying alignment and insuring that the cylinder
block pistons spring back and forth. Install end
cap bolts (4). Tighten, reference Table 4, page
16, torque values.
10
BDP-10A/16A/21L
44
6
4
Figure 22. BDP-10A
3
1
31
5
2
24
REMOVAL, INSPECTION AND ASSEMBLY OF THE END CAP AND
VALVE PLATE BDP-16A
Refer to figure 23.
Disassembly BDP-16A
1. Using any combination of two, 9/16” wrenches
or 9/16” socket and rachet drive, loosen the end
cap bolts (58) evenly.
This is normal. Grooving in the plate, or material
transfer that is evident when the surface is
checked by dragging a fingernail across it, would
be cause for replacement of the valve plate.
3. Inspect and replace alignment pins (26) if bent
or distorted.
4. Replace the housing O-ring (28) with a new
O-ring before reassembly.
Assembly BDP-16A
2. Keeping the end cap (25) held in place remove the four end cap bolts (58).
3. Slowly remove the end cap (25).
4. Remove the valve plate (29).
5. Remove housing alignment pins (26).
6. Remove housing gasket (28).
Inspection BDP-16A
1. Inspect the end cap (25) body for damage,
nicks or unusual wear patterns. Replace if necessary.
2. Inspect the running surface (side that contacts
the cylinder block) of the valve plate (29). The
running surface may show evidence of minor
abrasive rings.
1. Install housing O-ring (28) into housing O-ring
seat in housing (15).
2. Install alignment pins (26) into housing (15).
3. Lubricate the valve plate prior to installation.
Install valve plate (29) so the stamped letters “UP”
on the valve plate are facing up toward the
endcap.
4. Install end cap (25). Before installing the four
end cap bolts (58), push down on end cap (25)
verifying alignment and insuring that the cylinder
block pistons spring back and fourth. Install end
cap bolts. Tighten, per Table 5, page 16, torque
values.
25
56
56
40
58 x4
44
25
Figure 23. BDP-16A
29
26
28
26
15
BDP-10A/16A/21L
REMOVAL, INSPECTION AND ASSEMBLY OF THE END CAP AND
VALVE PLATE BDP-21L
Refer to figure 24.
Disassembly BDP-21L
1. Using any combination of two, 9/16” wrenches
or 9/16” socket and rachet drive, loosen the end
cap bolts (58) evenly.
This is normal. Grooving in the plate, or material
transfer that is evident when the surface is
checked by dragging a fingernail across it, would
be cause for replacement of the valve plate.
3. Inspect and replace alignment pins (26) if bent
or distorted.
4. Replace the housing O-ring (28) with a new
O-ring before reassembly.
Assembly BDP-21L
2. Keeping the end cap (25) held in place remove the four end cap bolts (58).
3. Slowly remove the end cap (25).
4. Remove the valve plate (29).
5. Remove housing alignment pins (26).
6. Remove housing gasket (28).
Inspection BDP-21L
1. Inspect the end cap (25) body for damage,
nicks or unusual wear patterns. Replace if necessary.
2. Inspect the bronze side of the valve plate
(29). The running surface may show evidence
of minor abrasive rings.
1. Install housing O-ring (28) into housing O-ring
seat in housing (15).
2. Install alignment pins (26) into housing (15).
3. Lubricate the valve plate prior to installation.
Install valve plate (29) with the bronze side down,
contacting the cylinder block.
4. Install end cap (25). Before installing the four
end cap bolts (58), push down on end cap (25)
verifying alignment and insuring that the cylinder
block pistons spring back and fourth. Install end
cap bolts. Tighten, per Table 6, page 16, torque
values.
15
BDP-10A/16A/21L
56 x2
26
29
40
39
41
25
44
58 x4
Figure 24. BDP-21L
26
28
26
REMOVAL, INSPECTION AND ASSEMBLY OF THE CYLINDER BLOCK
BDP-10A
Refer to Figure 25.
Disassembly BDP-10A
Assembly BDP-10A
1. Install piston seats into the end of the pistons.
2. Install springs into the pistons.
3. Install one at a time, pistons, springs and seats
as one assembly into the cylinder block.
1. Tilt the BDP on its side, drain remaining oil.
Lift out the cylinder block assembly (25).
2. Remove the pistons, springs and piston seats.
Inspection BDP-10A
1. Inspect the running surface of the cylinder
block and piston ends for damage, nicks or unusual wear patterns. The running surface may
show evidence of minor abrasion . This will be a
normal wear. If grooved or smeared, replace with
a new cylinder block assembly.
2. Inspect the piston springs for distortion or
breakage. If necessary, replace with new cylinder block kit.
3. Inspect the piston seats. Residual oil may
cause these to remain stuck to the inside of the
pistons.
4. With the BDP housing tilted on its side, install
the cylinder block assembly (25) with pistons contacting the thrust bearing.
NOTE: To check that piston placement
is correct, push downward on the cylinder block assembly (38). If this results in
a spring action the block assembly has
been installed correctly. If this cannot be
accomplished, remove and reassemble
the block assembly. Place a rubber band
around the cylinder block pistons to hold
them in position during installation. Then
after installation cut the rubber band and
remove it. Check for cylinder block assembly for spring action.
27
Piston
Piston
Seat
Spring
Cylinder
Block
25
Figure 25. BDP-10A
BDP-10A/16A/21L
REMOVAL, INSPECTION AND ASSEMBLY OF THE CYLINDER BLOCK
BDP-16A/21L
Refer to Figure 26.
Disassembly BDP-16A/21L
Assembly BDP-16A/21L
1. Install piston seats into the end of the pistons.
2. Install springs into the pistons.
3. Install one at a time, pistons, springs and seats
as one assembly into the cylinder block.
1. Tilt the BDP on its side, drain remaining oil.
Lift out the cylinder block assembly (38).
2. Remove the pistons, springs and piston seats.
Inspection BDP-16A/21L
1. Inspect the running surface of the cylinder
block and piston ends for damage, nicks or unusual wear patterns.
The running surface may show evidence of minor abrasion . This will be normal wear. If
grooved or smeared, replace with a new cylinder block assembly.
2. Inspect the piston springs for distortion or
breakage. If necessary, replace with new cylinder block kit.
3. Inspect the piston seats. Residual oil may
cause these to remain stuck to the inside of the
pistons.
4. With the BDP housing tilted on its side, install
the cylinder block assembly (38) so that the
pistons contact the thrust bearing.
NOTE: To check that piston placement
is correct, push downward on the cylinder block assembly (38). If this results in
a spring action the block assembly has
been installed correctly. If this cannot be
accomplished, remove and reassemble
the block assembly. Place a rubber band
around the cylinder block pistons to hold
them in position during installation. Then
after installation cut the rubber band and
remove it. Check for cylinder block assembly for spring action.
Cyli nder
Block
Figure 26. BDP-16A/21L
BDP-10A/16A/21L
Piston
Seat
Piston
(7x)
(7x)
Spring
38
(7x)
28
REMOVAL, INSPECTION AND ASSEMBLY OF BLOCKSPRING, THRUST
WASHER, AND THRUST BEARING,
BDP-10A/16A
Refer to Figure 27.
Disassembly BDP-10A/16A
1. Remove the block spring (29/20).
2. Remove the thrust washer (30/19).
3. Remove the thrust bearing and race (34/17).
Inspection BDP-10A/16A
1. Inspect and replace the block spring (29/20)
and thrust washer (30/19) if they are distorted
or broken.
REMOVAL, INSPECTION AND ASSEMBLY OF THRUST BEARING,
BDP-21L
Refer to Figure 28.
Disassembly BDP-21L
1. Remove the thrust bearing and race (17).
Inspection BDP-21L
1. Inspect the running surface of the bearing
race for damage (17), nicks or unusual wear patterns. The running surface may show evidence
of minor abrasion . This will be normal wear.
Inspect the bearings for free movement. Inspect
the bearing cage for distortion or damage. Replace if necessary.
2. Inspect the running surface of the bearing
race for damage, nicks or unusual wear patterns.
The running surface may show evidence of minor abrasion . This will be normal wear. Inspect
the bearings for free movement. Inspect the
bearing cage for distortion or damage. Replace
if necessary.
Assembly BDP-10A/16A
1. Install thrust bearing and race assembly
(34/17).
NOTE: The difference in race thickness:
The thin race seats into the swashplate
(32/31). The thicker race will be installed
toward the piston noses.
2. Install thrust washer (30/19).
3. Install block spring (29/20).
Assembly BDP-21L
1. Install bearing and race assembly (17).
NOTE: The difference in race thickness:
The thin race seats into the swashplate.
The thicker race will be installed toward
the piston noses.
17
Figure 28. BDP-21L
29
34/17
30/19
29/20
Figure 27. BDP-10A/16A
BDP-10A/16A/21L
REMOVAL, INSPECTION OF
SWASHPLATE, INSPECTION OF
CRADLE BEARINGS BDP-10A/16A
REMOVAL, INSPECTION AND ASSEMBLY OF SWASHPLATE, AND
CRADLE BEARINGS, BDP-21L
Refer to Figure 29.
Disassembly BDP-10A/16A
1. Remove the swashplate(32/31).
Inspection BDP-10A/16A
1. Inspect the running surface of the bearing
pocket for damage (32/31), nicks or unusual
wear patterns. The running surface may show
evidence of minor abrasion . This will be normal wear. Inspect the cradle bearing side of the
swashplate (32/31) for damage. Replace if necessary.
2. Inspect the cradle bearings attached to the
inside of housing (1/15) for normal wear patterns,
placement, and insure they are staked in place.
If damaged, replace housing (1/15).
NOTE: The cradle bearings will have discoloration due to normal wear. This, under normal circumstances, will not warrant replacement.
Refer to Figure 30.
Disassembly BDP-21L
1. Remove the swashplate (31).
Inspection BDP-21L
1. Inspect the running surface of the bearing
pocket for damage (31), nicks or unusual wear
patterns. The running surface may show evidence of minor abrasion . This will be normal
wear. Inspect the cradle bearing side of the
swashplate (31) damage. Replace if necessary.
2. Inspect the cradle bearings attached to the
inside of housing (15) for normal wear patterns,
placement, and insure they are staked in place.
If damaged, replace housing (15).
NOTE: The cradle bearings will have discoloration due to normal wear. This under normal circumstances will not warrant replacement.
Assembly BDP-10A/16A
1. Install swashplate (32/31) by holding trunnion
arm’s (37/13) slot guide (38/14) with the aide of
a flat tip screwdriver. Use the screwdriver to hold
the slot guide (38/14) in place while positioning
the swash plate (32/31) onto the cradle bearing
in the housing (1/15).
2. Rotate trunnion arm (37/13) to assure
swashplate pivoting action.
32/31
34
30
29
Figure 29 . BDP-10A/16A
BDP-10A/16A/21L
(Cradle Bearings cannot be
removed from housing as depicted)
38/14
37/13
1/15
Assembly BDP-21L
1. Install swashplate (31) by holding trunnion
arm’s (13) slot guide (14) with the aide of a flat
tip screwdriver. Use the screwdriver to hold the
slot guide (14) in place while positioning the
swash plate (31) onto the cradle bearing in the
housing (15).
2. Rotate trunnion arm (13) to assure swashplate
pivoting action.
13
14
31
17
(Cradle Bearings cannot be
removed from housingas depicted)
Figure 30 . BDP-21L
15
30
REMOVAL, INSPECTION AND ASSEMBLY OF INPUT SHAFT BDP10A
Refer to Figure 31.
Note: If trunnion arm is to be removed,
delay reassembly of input shaft assembly.
Disassembly BDP-10A
1. Remove the retaining ring (22).
2. Remove the lip seal (20).
3. Remove the spacer (21).
4. Remove the shaft assembly (18) from the BDP.
Inspection BDP-10A
1. Inspect the input shaft (18) for worn splines,
surface damage, or keyway damage. Replace
shaft assembly if necessary.
2. Inspect the bearing (19) for evidence of scoring, corrosion, or damage. Replace shaft assembly if necessary.
3. Inspect and replace the spacer (21) if it is
bent or broken.
4. Inspect and replace the retaining ring (22) if
it is bent or broken.
Assembly BDP-10A
Note: 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
clean petroleum jelly prior to assembly.
Also, protect the inner diameter of seals
by covering the shaft with plastic wrap.
1. Install input shaft assembly (18) into the hous-
ing (1) bore. Light tapping with a rubber mallet
may be necessary on the input shaft (18) once
the bearing is aligned with the housing (1) bore.
Rotate the input shaft (18) to insure free movement.
2. Install spacer (21).
3. Install new lip seal (20).
4. Install retaining ring (22).
Note: Replace the input shaft seal (20)
after removal.
18
1
22
20
21
23
19
31
Figure 31. BDP-10A
BDP-10A/16A/21L
REMOVAL, INSPECTION AND
ASSEMBLY OF INPUT SHAFT,
BDP-16A/21L
Refer to Figure 32.
4. Inspect and replace the retaining ring (3) if it
is bent or broken.
Note: If trunnion arm is to be removed,
delay reassembly of input shaft assembly.
Disassembly BDP-16A/21L
1. Remove the retaining ring (3).
2. Remove the lip seal (6).
3. Remove the spacer (4).
4. Remove the shaft assembly (1) from the BDP.
Inspection BDP-16A/21L
1. Inspect the input shaft (1) for worn splines,
damage, or keyway damage. Replace shaft
assembly if necessary.
2. Inspect the bearing (5) for evidence of scoring, corrosion, or damage. Replace shaft assembly if necessary.
3. Inspect and replace the spacer (4) if it is bent
or broken.
Note: Replace the input shaft seal (6) after removal.
5. Inspect and replace the thrust spring (20) and
thrust washer (19) if they are distorted or broken.
Assembly BDP-16A/21L
Note: 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
clean petroleum jelly prior to assembly.
Also, protect the inner diameter of seals
by covering the shaft with plastic wrap.
1. Install the shaft (1) assembly, into the housing
(15) bore. Light tapping with a rubber mallet may
be necessary on the input shaft (1) once the bearing is aligned with the housing bore (15). Rotate
the input shaft (1) to insure free movement.
2. Install the spacer (4).
3. Install a new lip seal (6).
4. Install the retaining ring (3).
BDP-10A/16A/21L
3
6
5
4
2
2
15
1
Figure 32. BDP-16A/21L
19
20
32
REMOVAL, INSPECTION TRUNNION
ARM BDP-10A/16A
REMOVAL, INSPECTION TRUNNION
ARM BDP-21L
Refer to Figure 33.
Disassembly BDP-10A/16A
1. Remove and discard the trunnion seal retainer
and seal (49/12).
2. Remove the slot guide (38/14).
3. Remove the trunnion arm (37/13).
Inspection BDP-10A/16A
1. Inspect the trunnion arm (37/13) for wear or
damage. Replace the trunnion arm if necessary.
Assembly BDP-10A/16A
1. Install the trunnion arm (37/13) into the housing (1/15) bore. Rotate the trunnion arm to insure free movement.
2. Install a new seal and seal retainer.
Refer to Figure 34.
Disassembly BDP-21L
1. Remove trunnion seal retainer (10) and seal
(12).
2. Remove slot guide (14).
3. Remove trunnion arm (13).
Inspection BDP-21L
1. Inspect the trunnion arm (13) for wear or dam-
age. Replace trunnion if necessary.
Assembly BDP-21L
1. Install the trunnion arm (13) into the housing
(15) bore. Rotate the trunnion arm to insure free
movement.
2. Install a new seal and seal retainer.
3. To completely reassemble the pump, refer to
the assembly steps on pages 19-33. Begin with
the trunnion arm assembly steps listed on page
33 and complete the assembly steps in reverse
order working towards the front of the manual.
Note: 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
clean petroleum jelly prior to assembly.
Also protect the inner diameter of seals
by covering the shaft with plastic wrap.
Remove the plastic wrap after the seal is
installed.
1/15
3. To completely reassemble the pump, refer to
the assembly steps on pages 19-33. Begin with
the trunnion arm assembly steps listed on page
33 and complete the assembly steps in reverse
order working towards the front of the manual.
Note: 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
clean petroleum jelly prior to assembly.
Also protect the inner diameter of seals
by covering the shaft with plastic wrap.
Remove the plastic wrap after the seal is
installed.
16
13
14
10
12
33
38/14
37/13
49/12
Figure 33. BDP-10A/16A
Figure 34. BDP-21L
BDP-10A/16A/21L
NOTES
BDP-10A/16A/21L
34
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85 - Overhaul Seal Kit
BDP-21L
Figure 35. BDP-21L
BDP-10A/16A/21L
ITEMS LIST BDP-21L
Part numbers are not provided in this manual. See microfiche or CD for part numbers.
Retaining Ring
4Spacer
5Shaft Ball Bearing
6Lip Seal 17 x 47 x 8 PTCN1
10Trunion Seal Retaining Ring
12Lip Seal 15 x 27 x 7
13Trunnion Arm
14Slot Guide
15Housing Kit
17Thrust Ball Bearing Assembly
19Block Thrust Washer
20Block Spring
25Endcap Kit (w/poppets)
End Cap Kit (w/ poppets, .078” cooling orifice)
End Cap Kit (w/SCR'S)
End Cap Kit (Aux w/ poppets)
End Cap Kit (Aux w/ SCR's)
End Cap Kit (Aux w/LH:SCR and RH:poppet)
End Cap Kit (w/LH: poppet and RH:SCR)
26Pin
28O-Ring
29Valve Plate
31Variable Swashplate
38Cylinder Block Kit
39O-Ring
Bypass Valve Kit (.043” orifice)
54Auxiliary Filter Kit
56Socket Hd Cap Screw (M8 x 1.25-25mm)
Flange Hd Screw (5/16-18 x 2.5)
58Hex Screw, Flanged Hd (M10 x1.50-65mm)
69Dowel Pin
99Overhaul Seal Kit
BDP-10A/16A/21L
Table 8. BDP-16A
38
104
22
20
103
104
100
101
106
102
19
21
37
38
32
34
30
29
85
6
18
25
31
98
107
1
3
44
105
94
42B
49
OR
5
56
42B
2
OR
110
66
OBSOLETE
100 - Overhaul Seal Kit
15
35
10
BDP-10A
42A
SIDE)
(PORT "A"
90
OR
OR
OBSOLETE
69
7
6
59
SIDE)
42A
(PORT "A"
59
75
45
44
4X 4
8
7
6
10
56
54
66
10
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39
Figure 37. BDP-10A
BDP-10A/16A/21L
ITEMS LIST BDP-10A
Part numbers are not provided in this manual. See microfiche or parts manual for part numbers.
No.Description
1Housing Kit
2End Cap Kit (W/ Poppets, Standard Charge)
End Cap Kit (W/ SCR'S, Standard Charge)
End Cap Kit (W/ Poppets, Auxiliary Charge)
End Cap Kit (W/ SCR'S & Auxiliary Charge)
End Cap Kit (STD CHG) LH:SCR / RH:Poppet
End Cap Kit (STD CHG) LH:Poppet / RH:SCR
End Cap Kit (AUX CHG) LH:SCR / RH:Poppet
End Cap Kit (AUX CHG) LH:Poppet / RH:SCR
End Cap Kit (STD CHG) LH:SCR / RH:Poppet,Thru
End Cap Kit (STD CHG) W/Poppets, Thru
End Cap Kit (STD CHG) W/SCR’s, Thru
End Cap Kit (STD CHG) LH:Poppet/ RH:SCR,Thru
3Straight Headless Pin
4Hex Flange Bolt M8-1.25 X 60mm LG
5Housing O-Ring
6Charge Pump Kit (STD)
Pump Shaft Kit (Tapered)
19Ball Bearing 17 x 40 x 12
20Lip Seal 17 x 40 x 7 PTC
21Spacer
22Retaining Ring
25Cylinder Block Kit
29Block Spring
30Block Thrust Washer
31Valve Plate (Steel N-Tec:Black)
32Swashplate
No.Description
34Ball Thrust Bearing
35Stud, Torque
37Trunnion Arm