Hydro-Gear HGM-H Series Installation and operating manual

BLN-0043
January 2018
HGM-H™ Series Motor
Service and Repair Manual

HGM-H i
TABLE OF CONTENTS
Foreword ................................ . . .1
Description and Operation .................. . . .2
Introduction .............................. . . .2
General Description ......................... 2
External Features ......................... . . .4
Technical Specifications ......................5
Product Identification ........................5
Safety .................................... 6
Personal Safety........................... . . .6
Tool Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Work Area Safety ......................... . . .6
Troubleshooting........................... . . .7
Work Area Safety ......................... . . .8
Service and Maintenance ................... . . .8
External Maintenance ...................... . . .8
Service and Maintenance Procedures ......... . . .8
Fluids................................... . . .8
Fluid Volume and Level..................... . . .8
Fluid Change Procedure .................... . . .8
Purge Procedure.......................... . . .9
Tear Down and Reassembly ................. . .10
How to Use This Manual.................... . .10
General Instructions ....................... . .10
Tools ................................... . .11
Torques ................................. . .11
Hydraulic Motor Removal ................... . .12
Axle Hub Assembly........................ . .13
Brake Arm Assembly....................... . .14
Side Housing............................. . .15
Axle Shaft and Planetary Gear Set............ . .16
Bearing and Motor Block Cap................ . .17
Motor Block .............................. . .18
Motor Shaft and Brake Disc ................. . .19
Brake Shaft and Cam ...................... . .20
Screw Tightening Sequence ................. . .21
Sealant Path ............................. . .21
Castle Nut Alternate Torque Method........... . .22
Assembly After a Complete Teardown ......... . .23
Drive Motor Exploded View.................. . .24
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Glossary of Terms. . . . . . . . . . . . . . . . . . . . . . . . 26-27
Notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28-29

HGM-H 1
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 recog-
nized 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®HGM-H™
series motor.
Also included is a glossary of terms that are
frequently used throughout the industry and in
Hydro-Gear service publications. Understand-
ing 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 pre-
ferred methods of repair.
Internal repair procedures require that the
HGM-H series motor be removed from the
vehicle.
FOREWORD

2 HGM-H
movement out of the cylinder block, it gets
pushed back into the cylinder and uid inside
the piston is discharged through the low pres-
sure port of the motor. Pistons develop torque
only through half of the cylinder block rotation
cycle. Therefore, multiple pistons are used to
provide a constant and continuous torque to
the motor shaft. Reversing the direction of the
incoming pressurized uid into the motor re-
versesthedirectionof themotoroutputrotation.
A hydraulic bypass is utilized in a hydraulic
system 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. The bypass will be
located on the hydraulic pump.
The HGM-H series motor utilizes a friction
type brake controlled by a cam attached to an
external actuating arm.
INTRODUCTION
The purpose of this manual is to provide in-
formation useful in servicing the Hydro-Gear®
HGM-H series motor. This manual includes
the HGM-H series motor general description,
hydraulic schematic, technical specications,
servicing and troubleshooting procedures.
Shouldservicing be required, theexteriorof the
motorwill needtobe thoroughly cleanedbefore
beginning most procedures. Do not wash the
transaxlewhile it is hot.Do not use a pressure
washer to clean the unit.
GENERAL DESCRIPTION
The HGM-H series hydraulic motors are xed
displacement axial piston motors. The motor
is designed to convert hydraulic power into ro-
tational power at the axle shaft. It operates at
an innitely variable speed range between zero
andmaximum axle speed determined bymotor
displacement and maximum pump ow in both
forward and reverse modes of operation.
The HGM-H series motor is available with a
xed displacement of 15 cu. in. or 18 cu. in. (245
to294cc)maximumperrevolution.Thecylinder
block pistons in the HGM H series motors are
set at a xed displacement by a swash angle
thatis integral to themotorhousing. Therefore,
themotoris always at maximum displacement.
As pressurized uid from the pump pushes
against the cylinder block pistons, they forced
to rotate with the thrust bearing.As the pistons
rotatewiththethrustbearing,theycreatetorque
androtory motion that is transmittedtothe axle
shaft. Torque continues to develop as long as
the piston is being pushed out of the cylinder
block. When the piston reaches the end of the
DESCRIPTION AND OPERATION

4 HGM-H
EXTERNAL FEATURES HGM-H SERIES MOTORS
— Top View—
— Back View—
— Side View—
WHEEL HUB
HUB NUT COVER
BRAKE ARM
HYDRAULIC HOUSING CAP
FILL PORT / OPTIONAL CASE DRAIN
“B” PORT
“A” PORT
“B” PORT
“A” PORT
“A” & “B” PORTS
BRAKE ARM
MOUNTING HOLE X 4
FILL PORT / OPTIONAL CASE DRAIN
BRAKE ARM
WHEEL HUB
HUB NUT COVER
Figure 1, External Features

HGM-H 5
TECHNICAL SPECIFICATIONS
HYDRO-GEAR
HGM-15H-XXCK
1 192 X 10428 Assembled in USA
Model Number
Year Built
Date (Julian- Day of year) Serial Number (unique for that model - for that day)
Type of Product and Build Information
PRODUCT IDENTIFICATION
The model and conguration of the HGM-H can be determined from the label found on the
transaxle.
HGM-H™Piston Motor tECHniCAL sPECiFiCAtions
Geometric Displacement 15 in3/rev (245.81 cc/rev) 18 in3/rev (294.97 cc/rev)
Maximum Speed
Continuous
Intermittent
210 rpm
250 rpm 185 rpm 210 rpm
Maximum Torque
Peak
Continuous
Intermittent
6600 in-lbf (75 N-m)
2700 in-lbf (30 N-m)
4900 in-lbf (75 N-m)
7900 in-lbf (89 N-m)
3200 in-lbf (36 N-m)
5900 in-lbf (64 N-m)
Maximum Oil Flow
Continuous
Intermittent
9.4 hp (7 KW)
20.5 hp (15.4 kW)
Axle Shaft Diameter 1.375 in (34.925 mm)
Axle Shaft End Options 4 Bolt Flange
5 Bolt Flange
Parking Brake Type Internal Wet Disc
Max. weight applied to shaft/housing
Wheel Load Force - Radial 840 lbf (381 kg)
Weight of Unit 38.2 lb (17.3 kg)
Figure 2, Product Label

6 HGM-H
SAFETY
This symbol points out important safety
instructionswhich, if not followed,couldendan-
gerthe personal safety and/or propertyofyour-
selfand others. Read andfollowallinstructions
in this manual before attempting maintenance
on your hydraulic motor. When you see this
symbol - HEED ITS WARNING.
WARNING
POTENTIAL FOR SERIOUS INJURY
Inattention toproper safety, operation,or
maintenance procedures could result in
personal injury, or damage to the equip-
ment. Before servicing or repairing the
hydraulic motor, fully read and under-
stand the safety precautions described
in this section.
PERSONAL SAFETY
Certain safety precautions must be observed
whileservicing or repairing the hydraulic motor.
This section addresses some of these precau-
tionsbutmustnotbe consideredan 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 regula-
tions.
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 person-
nel 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.
Inspecteach toolbefore useand replaceany 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 oor should be clean and dry, and all ex-
tension cords or similar trip hazards should be
removed.
SERVICING SAFETY
Certainprocedures may requirethe vehicle tobe
disabledin order toprevent possible injury tothe
servicing technician and/or bystanders.
Thelossof hydrostatic drivelinepower mayresult
in the loss of hydrostatic braking capability.
Some cleaning solvents are ammable. Use only
approved cleaning materials: Do not use explo-
sive or ammable liquids to clean the equipment.
To avoid possible re, do not use cleaning sol-
vents in an area where a source of ignition may
be present.
“Discard used cleaning material in the ap-
propriate containers according to local, state,
and federal regulations.”

HGM-H 7
TROUBLESHOOTING
In many cases, problems with a hydraulic sys-
tems are not related to a defective hydraulic
unit, but are caused by slipping drive belts,
partially engaged bypass valves, and loose or
damaged control linkages. Be sure to perform
alloperational checksandadjustmentsoutlined
in Service and Maintenance, before assuming
the hydraulic system is malfunctioning. The
table below provides a troubleshooting check-
list to help determine the cause of operational
problems.
WARNING
Do not attempt any servicing or ad-
justments with the engine running.
Use extreme caution while inspecting
the drive belt assembly and all vehicle
linkage!
Follow all safety procedures outlined in
the vehicle owner’s manual.
TROUBLESHOOTING CHECKLIST
Possible Cause Corrective Action
Unit Operates In One Direction Only
Control linkage bent or out of adjustment Repair or replace linkage on vehicle pump assembly, Page 8
Drive belt slipping or pulley damaged Repair or replace belt/pulley on vehicle pump assembly, Page 8
Vehicle Does Not Drive/Track Straight
Vehicle tires improperly inated Refer to vehicle manufacturer suggested tire pressure
Control linkage bent or out of adjustment Repair or replace linkage on vehicle pump assembly, Page 8
Drive belt slipping or pulley damaged Repair or replace belt/pulley on vehicle pump assembly, Page 8
Brake Partially Engaged Disengage Brake, Replace damaged brake components, Page 14
Unit Is Noisy
Oil level low or contaminated oil Fill to proper level or change oil, Page 8
Excessive loading Reduce vehicle loading, Page 8
Loose parts Repair or replace loose parts
Air trapped in hydraulic system Purge hydraulic system, Page 9
Brake Partially Engaged Disengage Brake, Replace damaged brake components, Page 14
Unit Has No/Low Power
Engine speed low Adjust to correct setting
Control linkage bent or out of adjustment Repair or replace linkage on vehicle pump assembly, Page 8
Drive belt slipping or pulley damaged Repair or replace belt/pulley on vehicle pump assembly, Page 8
Oil level low or contaminated oil Fill reservoir to proper level or change oil, Page 8
Excessive loading Reduce vehicle loading, Page 8
Air trapped in hydraulic system Purge hydraulic system, Page 9
Brake Partially Engaged Disengage Brake, Replace damaged brake components, Page 14
Unit Is Operating Hot
Debris buildup around transaxle Clean off debris, Page 8
Oil level low or contaminated oil Fill to proper level or change oil, Page 8
Excessive loading Reduce vehicle loading, Page 8
Air trapped in hydraulic system Purge hydraulic system, Page 9
Brake Partially Engaged Disengage Brake, Replace broken, missing or frozen return spring
Transaxle Leaks Oil
Damaged seals, housing, or gaskets Replace damaged components
Air trapped in hydraulic system Purge hydraulic system, Page 9

8 HGM-H
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. Do not use a pressure
washer to clean the transaxle.
FLUIDS
The uids used in Hydro-Gear products have
been carefully selected, and only equiva-
lent, 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 anAPI
classication of SL is recommended. Refer to the
vehicle manufacturer for recommended oil.
“All uids should be handled and disposed of
according to local, state, and federal regula-
tions.”
FLUID VOLUME AND LEVEL
Certain situations may require additional uid to
beadded or even replaced.In addition to lling
the hydraulic system with uid, an additional
34 . oz. (1000mL) will need to be added to the
case via the highest ll point of the HGM-H
unit. Reference page 4 for the proper ll loca-
tion. Refer to the vehicle manufacturer’s recom-
mendations for the proper ll location and level of
thecompletehydraulicsystem.Aftermaintenance
oroil change, followpurging procedures onpage
9 and check the uid level once the unit has been
purged and operated for 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
on page 9 after changing uids.
FILTERS
An inlet lter is required to insure that only clean
uid enter the system. Refer to the vehicle manu-
facturer for approved lter replacement.
SERVICE AND MAINTENANCE
EXTERNAL MAINTENANCE
Regular external maintenance of the hydraulic
motor should include the following:
1. Checkthevehicle operator’smanual for the
recommended load ratings. Insure that the
current application does not exceed load
rating.
2. Checkreservoiroillevelinaccordance with
the vehicle manufacturers recommenda-
tions.
3. Inspectthevehicle drive belt, idlerpulley(s),
and idler spring(s). Insure that no belt slip-
page can occur. Slippage can cause low
input speed to the pump resulting in low
ow to the hydraulic motor.
4. Inspect the vehicle control linkage to the
directionalcontrol armon thevehiclespump
assembly.
5. Inspect the hydraulic motors and pumps
for debris. Keeping the units debris free is
important in the overall performance of the
unit.
6. Inspect all external plumbing for possible
leaks or loose ttings. An air leak may be
difcult to detect on the “suction side” or inlet
line to the pump. Refer to Purging Proce-
dure on page 9.
SERVICE AND MAINTENANCE
PROCEDURES
Some of the service procedures presented on
thefollowing pages can be performed while the
transaxleismounted on the vehicle.Anyrepair
procedures as mentioned in the repair section
of this manual must be performed after the unit
has been removed from the vehicle.
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 us-
ing a solvent wash and air drying is usually
adequate. As with any precision equipment,

HGM-H 9
SERVICE AND MAINTENANCE
PURGING PROCEDURE
The HGM-H motor can not be purged of air
as a stand alone component. The hydraulic
system as a whole will need to be purged after
any addition of oil to the system or a complete
oil change. This will most likely involve the use
of the hydraulic pumps bypass feature. If this
is not available, see the manufacturers recom-
mendation for air purging.
Due to the effects air has on efciency in hy-
drostatic drive applications, it is critical that air
is removed or purged from the system.
These purge procedures must be preformed
anytimea hydrostatic systemhasbeen opened
for maintenance or repair, or if any additional
oil has been added to the system.
Air creates inefciency because it has compres-
sion and expansion rates that are higher than
that of oil.
Air trapped 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, ll to the vehicle
manufacturer’s specications.
Thefollowing procedures should be performed
with the vehicle drive wheels off the ground,
then repeated under normal operating condi-
tions.
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 techni-
cian and/or bystanders, insure the ve-
hicle is properly secured.
1. With the vehicles pump assembly bypass
valve open and the engine running, slowly
move the directional control in both forward
and reverse directions (10 to 20 times). As
air is purged from the unit, the oil level in
the reservoir may drop.
2. Withthebypassvalveclosedand theengine
running,slowlymove the directional control
in both forward and reverse directions (10
to 20 times). Check the oil level, and add
oil as required after stopping engine.
3. Itmaybenecessaryto repeat steps 1 and 2
untilall the air iscompletelypurgedfrom the
system. When the hydraulic system moves
forward and reverse at normal speed and
thereservoiroilremainsataconstantlevel,
purging is complete.

10 HGM-H
TEAR DOWN AND REASSEMBLY
HOW TO USE THIS MANUAL
Each subassembly illustrated in this manual is
illustrated with an exploded view showing the
parts involved. The item reference numbers
in each illustration are for assembly instruc-
tions only. See page 25 for part names and
descriptions. A complete exploded view and
item list of the transaxle 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 us-
ing 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
cavitiesfrom damage and foreign material.The
external surfaces should be cleaned before
beginning any repairs. Do not use a pressure
washer to clean the transaxle.
Uponremoval, itisrecommended that allseals,
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 during installation by covering the shaft
with a cellophane or plastic wrap material. Be
sure all remnants of this covering are removed
after servicing.
Parts requiring replacement must be replaced
from the appropriate kits identified in the
Items Listing, found at the end of this
manual.
Note: “Any and all Hydro-Gear components
removed and replaced during service are
recyclable.”

HGM-H 11
TOOLS
TORQUES
REQUIRED TOOLS
Miscellaneous Sockets
Three Jaw Puller 1/2”-3/8” Adapter
Flat Blade Screw Driver (2) 3/8” Deep
Torque Wrench 1-1/8” Deep
Air Impact Wrench 1/4” Allen
Rubber or Neoprene Mallet 3/4” Deep
Breaker Bar
Side Cutters/Snips
Needle Nose Pliers
Large External Snap Ring Pliers
Small Internal Snap Ring Pliers
REQUIRED TORQUE VALUES
Item Description Torque Operation
4 Screw, Housing 280-340 in-lbs (31.6-38.4 Nm) All Housing Screws
10 Nut, Axle, Castlelated 275-350 ft-lbs (372.9-474.5 Nm) Hub
56 Nut, Brake 600-800 in-lbs (67.8-90.4 Nm) Brake Shaft
80 Plug 9/16-16 (Metal) 110-170 in-lbs (12.4-19.2 Nm) Oil Input Port

12 HGM-H
MOTOR REMOVAL
NOTE: It is necessary to remove the HGM-H
Motorfromthe vehicle before perform-
ing the repair procedures presented in
this section.
Beforestarting any disassembly,make
certain that your work area is neat and
clean. Clean the external parts of the
transaxle.
The following procedures are pre-
sentedin the order recommendedfora
complete tear down of the transaxle.
Do not disassemble the unit any far-
ther than necessary to accomplish the
required repairs.
Reassembly is accomplished by per-
forming the “Assembly” portions of the
procedures. If the unit has been com-
pletely disassembled, a summary of
the assembly procedures, in the order
in which they should occur, is given on
page 23.
Figure 3, HGM-H Wheel Motor

HGM-H 13
AXLE HUB ASSEMBLY
9
10
11
18
17
Refer to Figure 4
1. Remove the axle cap and discard (9).
2. Remove the cotter pin and discard (18).
3. Remove the castle nut (10).
4. Remove the taper hub assembly (11) and
discard.
NOTE: A new hub will have to be ordered
to replace the discarded hub.
5. Remove the axle shaft key (17).
Inspection
1. Check all components for excessive wear
or damage. Replace if necessary.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
2. Whentighteningthecastle nut (10)*,referto
the table on page 11 for the required torque
values.
NOTE: Asageneralrule,usethelowendofthe
torque specication . Once at the speci-
ed torque, rotate castle nut clockwise
to align with nearest cotter pin hole.
*SEE PAGE 22 FORALTERNATE
TORQUE METHOD.
Figure 4, Hub Assembly

14 HGM-H
BRAKE ARM ASSEMBLY
59
83
58
84
60
82
81
57
Figure 5, Brake Arm Assembly
Refer to Figure 5
Disassembly
1. Remove all items previously discussed in
their recommended order.
2. Mark the orientation of the brake arm (59)
before removal.
3. Remove the retaining ring (60).
4. Remove the brake handle (59), spring (82)
and spring pin (83).
5. Remove the spring spacer (81) and brake
spacer (57).
5. Remove the dowel pin (84) and the seal
(58). Discard the seal.
NOTE: Only remove the seal (58) and dowel
pin (84) if damaged or worn, or if doing
a complete disassembly.
Inspection
1. Inspect all parts for wear or damage. Re-
place as necessary.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
2. Install new seal (58) from seal kit.

HGM-H 15
SIDE HOUSING
13
4 (X 12)
1
Figure 6, Side Housing
Refer to Figure 6
Disassembly
1. Remove all external items previously dis-
cussed in their recommended order.
2. Remove the seal (13) and discard.
3. Remove the twelve housing screws (4),
then separate axle housing (1) from middle
housing (2).
Inspection
1. Inspectthebearingandbushing areasinthe
side cover for excessive wear or damage.
Replace if necessary.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
2. Apply a bead of sealant around the perim-
eter of the middle housing face. See “Seal-
ant Application Diagram” on page 21.
NOTE: Remove all old sealant from the axle
housing (1) and the middle housing (2)
before applying new sealant.
3. Align the side housing (2) with the main
housing(1). Use care not tosmeartheseal-
ant bead.
4. Install the twelve housing screws (6). Re-
fer to the screw tightening pattern on page
21.
5. When tightening the fasteners, refer to the
table on page 11 for the required torque
values.
6. Install a new axle seal (13) from the seal
kit.

16 HGM-H
AXLE SHAFT AND PLANETARY GEAR SET
14 15
16
21
20
22 (X 3)
23
24
25 26
Figure 8, Planetary Gear Set
Figure 7, Planetary Gear Set
Refer to Figures 7 and 8
Disassembly
1. Remove all external items previously dis-
cussed in their recommended order.
NOTE: Note the location of the ring gear
tabs.
2. Remove the axle bearing (14) and washer
(15).
3. Remove the ring gear (21).
4. Remove the axle shaft (16) and planetary
assembly from the middle housing (2).
5. Remove the axle retaining ring (26), axle
shaft spacer (25), axle gear (24), planet
gears (22), sun gear (23) and the carrier
(20).
NOTE: The sun gear (23) and axle gear (24) are
pressed as one piece in some models.
(Figure 8a)
Inspection
1. Inspect all items of the planetary gear set
for wear and or damage.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
NOTE: When installing the ring gear assembly
— line up the ring gear tabs with the
housing tabs.
Ring Gear Tabs
Ring Gear
Axle Shaft (16)
Planetary Assembly
2
23 & 24
Figure 8a

HGM-H 17
BEARING AND MOTOR BLOCK CAP
45
47
46
6
4 (X 7)
3
Figure 9, Motor Block Cap and Bearing
Refer to Figure 9
Disassembly
1. Remove all external items previously dis-
cussed in their recommended order.
2. Remove the seven housing cap screws (4)
and the housing cap (3).
3. Remove the o-ring (6) and discard.
4. Remove the thrust bearing (45), retaining
ring (47) and washer (46). Discard the re-
taining ring (47)
Inspection
1. Inspect the races of the thrust bearing (80)
for wear or damage.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
2. Install new o-ring (6) and retaining ring (47)
from seal kit.
3. Place the thrust bearing assembly (45) so
the thick race contacts the motor block pis-
tons.
4. Install the seven housing screws (6). Refer
to the screw tightening pattern on page
21.
5. When tightening the fasteners, refer to the
table on page 11 for the required torque
values.
Motor Block Pistons

18 HGM-H
MOTOR BLOCK
40 41
42 43
Figure 10, Motor Block
Refer to Figure 10
Disassembly
1. Remove all external items previously dis-
cussed in their recommended order.
2. Removethemotorblockassembly(40)from
the middle housing (2).
3. Disassemblethemotor block assembly and
inspect all parts.
Inspection
1. Inspect the pistons (43), piston seats
(42), springs (41) and the motor cylinder
block (40) of the motor block assembly for
scratches and or wear. Replace the motor
block assembly if necessary.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
2. Apply a light coating of oil to all running sur-
facesto prevent scoring during reassembly.
2

HGM-H 19
MOTOR SHAFT AND AXLE BEARING
34
33
32
31
30
27
Figure 11, Motor Shaft and Brake Disc
Refer to Figure 11
Disassembly
1. Remove all external items previously dis-
cussed in their recommended order.
2. Remove the motor shaft (34), retaining ring
(30)and gear (31) out ofthemiddlehousing
(2).
3. Removethebrake rotor(32) andthewasher
(33).
4. Remove the inboard axle bearing (27).
Inspection
1. Inspect for scratches and or damage to the
brake rotor (32).
3. Inspect the gear (31) and motor shaft (34)
for wear or damage.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
2