Hydro-Gear HGM-C Installation and operating manual

HGM-C
LSHT Wheel Motor
Service and Repair Manual
BLN-52690
January 2018

i HGM-C LSHT Wheel Motor
Foreword ..................................................... 1
How to use this manual ............................... 2
General Instructions .................................... 2
General Description..................................... 2
Tools ............................................................ 3
Torques........................................................ 3
Exploded View/ Parts List............................ 18
Drum & Brake Assemblies........................... 4
Notes ........................................................... 19
Disassembly
Service Position........................................... 5
End Cover.................................................... 6
Gearwheel Set............................................. 7
Cardan Shaft ............................................... 7
Distributor Plate........................................... 8
Output Shaft ................................................ 8
Needle Bearing............................................ 9
Shaft Seal.................................................... 9
Check Valves............................................... 10
Assembly
Ball Bearing ................................................ 11
Check Valves.............................................. 12
Needle Bearing........................................... 12
Output Shaft ............................................... 13
Retaining Ring............................................ 14
Cardan Shaft .............................................. 14
Distributor Plate.......................................... 15
Gearwheel Set............................................ 15
End Cover................................................... 16
Table of Contents

HGM-C LSHT Wheel Motor 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 - C mo-
tor.
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 motor
be removed from the vehicle.
This is not a certication, test or study guide for
a certication test. If a technician is interested
in certication, they should contact an agent
representing OPEESA (Outdoor Power Equip-
ment and Engine Service Association) at (860)
767-1770 or their Hydro-Gear Central Service
Distributor. Many distributors will be hosting
certication 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 Technical Service Depart-
ment at [phone].
Forward

2 HGM-C LSHT Wheel Motor
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 18 for part names and
descriptions. A complete exploded view and
item number list of the HGM - C motor is on
page 18.
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. Clean all parts carefully with low
aromatic kerosene.
As with any precision equipment, all parts must
be kept free of foreign material and chemi-
cals.
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 seal and
O-rings be replaced. Before assembly, lubricate
all metal parts with hydraulic oil and lightly
grease rubber parts with petroleum jelly.
Parts requiring replacement must be replaced
from the appropriate kits identied in the Items
Listing, found at the end of this manual. Use
only original Hydro-Gear
®replacement parts
found in BLN-51427 (CD).
General Description
Hydro-Gear HGM-C wheel motors convert
hydraulic energy (pressure and oil ow) into
mechanical energy (torque and speed). Hydro-
Gear wheel motors are of a xed displacement
LSHT design. For a given displacement (size of
motor) the speed is determined by the oil ow
rate and the torque is determined by the pres-
sure differential.
The operating principle of the motor is based
on an internal gearwheel that moves about an
eccentric, while rotating and advancing on the
rollers in the external gearwheel.
As oil ow enters the working port it is directed
through internal cavities to ports in the bore of
the housing to valving slots on the output shaft
through the distributor plate to drive the gear-
wheel set. The cardan shaft rotates and trans-
fers mechanical energy from the gearwheel to
the output shaft.
How to Use This Manual
“All uids and cleaning materials should
be handled and disposed of according
to local, state, and federal regulations.”
Note: “Any and all Hydro-Gear components
removed and replaced during service are
recyclable.”

HGM-C LSHT Wheel Motor 3
REQUIRED TOOLS
Flat Blade Screw Driver (2)
Torque Wrench
Rubber or Neoprene Mallet
13mm Wrench
Snap Ring Removal Tool
3.5mm Screw tap
Hydraulic Press
REQUIRED TORQUE VALUES
Item Description Torque Operation
1 Castellated nut 160 - 210 ft-lbs
[217 - 284 Nm]
Brake Drum Assembly
22 Screw, Hex head 1/4-20 x 1.25” 354 in-lbs [40 Nm] End Cover
29 Bolt, 5/16-18 x .75 SHCS 180 - 240 in-lbs
[20.3 - 27.1 Nm]
Brake Assembly
TOOLS
As a general rule, use the low end of the torque specication on fasteners when reassembling the unit.
TORQUES

4 HGM-C LSHT Wheel Motor
Cotter Pin
Castellated Nut (1)
Drum Assembly
Brake Assembly
Bolt (29)
HGM Motor
Disassembly
1. Remove the cotter pin. See gure 1.
2. Remove the castellated nut (1). See gure
1.
NOTE: If the drum assembly or hub assembly
is removed from the axle shaft, the
drum/ hub assembly must be discarded
and replaced with a new assembly.
3. Remove the drum assembly. See gure 1.
4. Remove the four bolts (29) securing
the brake assembly to the HGM motor.
See gure 2.
5. Remove the brake assembly. See gure 2.
Inspection
1. Inspect the studs on drum for wear and/or
damage. Replace if necessary.
2. Inspect the brake assembly, i.e., the brake
shoes for wear and/or damage.
Assembly
1. Reassemble all parts in the reverse order
of disassembly.
2. When tightening the fasteners, refer to the
table on page 3 for the required torque val-
ues.
NOTE: As a general rule, use the low end of
the torque specication on fasteners
when reassembling the unit.
DRUM & BRAKE ASSEMBLY
Figure 1, Drum Assembly
Figure 2, Brake Assembly

HGM-C LSHT Wheel Motor 5
Castellated Nut (1)
Retaining Ring (2)
Holding Tools
Woodruff Key (6)
Plugs (8)
Figure 3, Identication Mark
1. To ensure correct alignment and location
during reassembly of motor parts, provide
a “V” shaped identication mark. See gure
3.
2. Remove the castellated nut (1).
See gure 4.
3. Remove the woodruff key (6) and the plastic
plugs or ttings (8), if installed. See gure
4. Drain oil from the motor.
4. Remove the retaining ring (2).
See gure 5.
5. Place the HGM-C motor into a holding
tool. See gure 6.
SERVICE PREPARATION
Figure 5, Retaining Ring
Figure 4, Nut, Woodruff Key and Plugs
Figure 6, Service position
Inspection
1. Inspect woodruff key (6) for wear or dam-
age.

6 HGM-C LSHT Wheel Motor
End Cover (19)
Screw (22)
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), and retaining ring (2).
See page 5.
2. Using a 13mm wrench — remove the seven
screws (22). See gure 7.
3. Remove the seven washers (23) and dis-
card.
4. Remove the end cover (19) by sliding the
end cover sideways, off the gearwheel set.
See gure 8.
Inspection
1. Inspect for wear or damage.
2. Inspect screws (22) – threads, for wear or
damage.
END COVER
Figure 7, Screws
Figure 8, End Cover

HGM-C LSHT Wheel Motor 7
Gearwheel Set (17)
Cardan Shaft (15)
O-ring (18)
GEARWHEEL SET
Figure 9, Gearwheel Set
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), retaining ring (2),
seven screws (22), seven washers (23), and
the end cover (19). See pages 5 and 6.
2. Remove the O-ring (18) and gearwheel set
(17). Discard O-ring (18). See gure 9.
Note: Placing ngers underneath gearwheel
set will help keep parts from falling
out.
3. Remove second O-ring (16), under gear-
wheel set, and discard.
4. Dismantle the gearwheel set for inspection
if contamination or damage is suspected.
Inspection
1. Inspect for wear or damage.
CARDAN SHAFT
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), retaining ring (2),
seven screws (22), seven washers (23),
end cover (19), and the gearwheel set (17)
with O-rings (16, 18). See gure 4 - 7.
2. Remove the cardan shaft (15).
See gure 10.
Inspection
1. Check for wear and/or damage to the indi-
vidual splines on the cardan shaft (15).
Figure 10, Cardan Shaft

8 HGM-C LSHT Wheel Motor
Distributor Plate (14)
O-ring (13)
Cardan Shaft (15)
Figure 12, Output Shaft
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), retaining ring (2),
seven screws (22), seven washers (23),
end cover (19), the gearwheel set (17) with
O-rings (16, 18), and cardan shaft (15).
See pages 4 - 7.
2. Remove the distributor plate (14).
3. Remove and discard the O-ring (13).
See gure 11.
Inspection
1. Inspect for wear or damage.
DISTRIBUTOR PLATE
Figure 11, Distributor Plate
OUTPUT SHAFT
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), retaining ring (2),
seven screws (22), seven washers (23),
end cover (19), the gearwheel set (17)
with O-rings (16, 18), cardan shaft (15),
distributor plate (14), and O-ring (13).
See pages 4 - 8.
2. Place the motor in a hydraulic press — re-
place the cardan shaft (15) and press out
the output shaft (7). See gure 12.
Inspection
1. Inspect for wear or damage.

HGM-C LSHT Wheel Motor 9
Housing (9)
Output Shaft (7)
Ball Bearing (3)
NEEDLE BEARINGSHAFT SEAL
Figure 14, Needle Bearing
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), retaining ring (2), seven
screws (22), seven washers (23), end cover
(19), gearwheel set (17) with O-rings (16, 18),
cardan shaft (15), distributor plate (14), O-
ring (13), output shaft (7) and the shaft seal.
See pages 4 - 9.
2. Remove the needle bearing (12) with a
pressing tool. See gure 14.
Note: The needles may fall out of the needle
bearing (12) during dismantling and can
be retrieved for re-use.
Inspection
1. Inspect for wear or damage.
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), retaining ring (2),
seven screws (22), seven washers (23), end
cover (19), gearwheel set (17) with O-rings
(16, 18), cardan shaft (15), distributor plate
(14), O-ring (13), and the output shaft (7).
See pages 4 - 8.
2. Using a holding tool, press ball bearing (3),
washer (4), and shaft seal (5) off the output
shaft (7). See gure 13.
Inspection
1. Inspect for wear or damage.
Figure 13, Output Shaft Seal

10 HGM-C LSHT Wheel Motor
CHECK VALVES
Disassembly
1. Remove castellated nut (1), woodruff key
(6), plastic plugs (8), retaining ring (2),
seven screws (22), seven washers (23), end
cover (19), gearwheel set (17) with O-rings
(16, 18), cardan shaft (15), distributor plate
(14), O-ring (13), output shaft (7) needle
bearing (12), And, from the output shaft
— remove ball bearing (3), washer (4), and
output shaft seal (5). See pages 4 - 9.
2. Remove the check valves (11) with a ground
3.5mm screw tap. See gure 15. The check
valves are pressed in and can be removed
by pulling on the tap.
Inspection
1. Inspect for wear or damage.
Figure 15, Check Valves
Check Valve (11)

HGM-C LSHT Wheel Motor 11
Bullet
Seal (5)
Seal (5)
Washer (4)
Output Shaft (7)
Pressing Tool
Output Shaft (7)
Ball Bearing (3)
Output Shaft (7)
Assembly
Note: Before assembly, lubricate all parts with
hydraulic oil and grease rubber parts
with clean petroleum jelly.
1. Place the bullet on the output shaft (7)
and mount the output shaft seal (5).
See gure 1.
2. Remove the bullet and mount the washer
(4). See gure 2.
3. Place the ball bearing (3) onto output shaft
(7) and press into position. See gure 3.
Figure 1, Bullet/Output Shaft Seal
BALL BEARING
Figure 3, Ball Bearing/Press Tool
Figure 2, Washer

12 HGM-C LSHT Wheel Motor
Pressing Tool
Needle Bearing (12)
Check Valves (11)
Housing (9)
Housing (9)
Assembly
1. Mount seal (5), washer (4), and ball bearing
(3) onto output shaft (7). See page 11.
2. Place the motor housing (9), with
holding fixture into hydraulic press.
See gure 4.
3. Install the two check valves (11) into their
bores. See gure 5.
4. Seat the check valves (11) by lighty tapping
with a rubber hammer. See gure 5.
CHECK VALVES
Figure 4, Service Position
Figure 5, Check Valve
NEEDLE BEARING
Assembly
1. Mount seal (5), washer (4), and ball bearing
(3) onto output shaft (7). See page 11.
2. Install the check valves (11).
3. Place the needle bearing (12) into mo-
tor housing (9), then; press into position.
See gure 6.
Figure 6, Needle Bearing

HGM-C LSHT Wheel Motor 13
Pressing Tool
Housing (9)
Output Shaft (7)
Commutation Slot
Front
Annular
Channel
Assembly
1. Mount seal (5), washer (4), and ball bearing
(3) onto output shaft (7). See page 11.
2. Install check valves (11), and needle bearing
(12). See page 12.
3. Rotate the motor housing (9) so that the
front (output shaft end) is pointing upward .
See gure 7.
4. The rear of the output shaft (7) must be
marked before tted into motor housing
(9). The mark must be positioned vertically
above a commutation slot leading up to the
front annular channel. See gure 8.
5. Grease the journals with hydraulic oil.
6. Position output shaft (7) over motor hous-
ing (9) and carefully lower into the motor
housing (9). Press the output shaft with ball
bearing, washer and seal into motor hous-
ing. See gure 9.
OUTPUT SHAFT
Figure 7, Motor Housing
Figure 8, Output Shaft
Figure 9, Output Shaft/Press Tool

14 HGM-C LSHT Wheel Motor
Retaining Ring (2)
Output Shaft Assembly
O-ring (13)
Output Shaft Assembly
Cardan Shaft (15)
Marking
Housing (9)
Figure 10, Retaining Ring
Assembly
1. Mount seal (5), washer (4), and ball bearing
(3) onto output shaft (7). See page 11.
2. Install check valves (11), needle bearing
(12) and output shaft assembly. See pages
12 - 13.
3. Mount the retaining ring (2).
See gure 10.
Note: Make sure that the retaining ring is fully
engaged in motor housing groove.
CARDAN SHAFT
Figure 12, Cardan Shaft Marks
(Motor housing not shown)
Figure 11, O-ring/Cardan Shaft
RETAINING RING
Assembly
1. Mount seal (5), washer (4), and ball bearing
(3) onto output shaft (7). See page11.
2. Install check valves (11), needle bearing
(12), output shaft assembly and retaining
ring (2). See pages 12 - 14.
3 Turn motor housing (9) so that its rear end
is upwards and install a new O-ring (13).
See gure 11.
4. Guide the cardan shaft (15) down into the
motor housing and into the output shaft
assembly. See gure 12. In case of differ-
ent spline lengths turn the cardan shaft to
ensure the long spline end is tted in the
output shaft.
5. Transfer marking from output shaft to car-
dan shaft. See gure 12.

HGM-C LSHT Wheel Motor 15
Distributor Plate (14) Indentations
Slots
O-ring (18)
O-ring (16)
Port Surface
Housing (9)
Gearwheel (17)
GEARWHEEL SETDISTRIBUTOR PLATE
Figure 13, Distributor Plate
Figure 14, Gearwheel Set/O-ring
Assembly
1. Mount seal (5), washer (4), and ball bearing
(3) onto output shaft (7). See page 11.
2. Install check valves (11), needle bearing
(12), output shaft assembly, retaining ring
(2), and O-ring (13). See pages 12 - 14.
3. Turn the distributor plate (14) so that the
slots are against the motor housing (9) and
indentation in the distributor plate is pointing
to port surface. See gure 13.
Assembly
1. Mount seal (5), washer (4), and ball bearing
(3) onto output shaft (7). See page 11.
2. Install check valves (11), needle bearing
(12), output shaft assembly, retaining ring
(2), O-ring (13), and distributor plate (14).
See pages 12 - 15.
3. Place new O-rings (16, 18) in the O-
ring grooves of the gearwheel set (17).
See gure 14.

16 HGM-C LSHT Wheel Motor
Figure 17, Washers & Screws
Gearwheel (17)
Rim
End Cover (19)
Figure 15, Gearwheel Set
Assembly
1. Install the end cover (19). See gure 16.
Align markings.
2. Install new washers (23) onto the end cover
screws (22). See gure 17.
Note: When tightening the screws, refer to the
table on page 3 for the required torque
values. Also refer to gure 18 for the
proper torque sequence.
Figure 16, End Cover
END COVER
Assembly
4. In gearwheel set (17) with non-through
splines place the gearwheel set (17) with
the recess in the spline hole facing down
towards the motor housing (9).
5. Fit the gearwheel set (17) on the cardan
shaft (15) so that the top of the tooth in the
external teeth of the gearwheel is vertically
over the mark on the cardan shaft.
6. Turn the gearwheel set (17) counter clock-
wise until the cardan shaft (15) and the
internal gearwheel slips over and engages
the splines.
7. Turn the gearwheel rim to line up the
screw holes. See gure 15. Alignment
marks made before disassembly should
line up.
GEARWHEEL SET (continued)
Top of Tooth
Mark
Cardan Shaft (15)
Screw (22)
Washer (23)

HGM-C LSHT Wheel Motor 17
Woodruff Key (6)
Castellated Nut (1)
Plastic Plugs (8)
1,8
3
5
72
4
6
End Cover Screw
(22), 1 of 7
Figure 19, Final Assembly
END COVER (continued)
Figure 18, Torque Sequence
Assembly
3. Install the woodruff key (6), nut (1) and
plastic plugs or ttings (8). See gure 19.
NOTE: If the drum assembly or hub assembly
is removed from the axle shaft, the
drum/ hub assembly must be discarded
and replaced with a new assembly.
4. Refer to page 4 for brake/hub installation
instructions.
Assembly

18 HGM-C LSHT Wheel Motor
1
2
4
5
3
6
78
9
11
12
13
14
15
16
17
18
19
20 23
22
200 Seal Kit
Contained in seal kit
HGM – C PARTS LIST
1 Castellated nut
2 Retaining Ring
3 Ball Bearing
4 Washer
5 Shaft Seal
6 Woodruff Key
7 Output Shaft
8 Plastic Plugs
9 Housing
11 Check Valve
12 Needle Bearing
13 O-ring
14 Distributor plate
15 Cardan Shaft
16 O-ring
17 Gearwheel set
18 O-ring
19 End Cover
20 Label
22 Screw
23 Washer
200 Seal Kit
Exploded View