2. Inspect the pressure plates for excessive wear. If deep
10. Install seal (2) in the bore of mounting flange (5). Press
the seal into position using a suitable driver and press,
curved wear marks are visible, the pressure plates should be
Install snap ring (1).
11. Coat O-ring (6) with a small amount of clean grease
3. Measure the gear journals at a point next to the face of
and install the O-ring in its groove in mounting flange (5).
the gear, and at a point 1/2 inch (12.7 mm) or more from
Install the mounting flange on body (24).
the gear face. Compare the two measurements. If the differ-
ence in the measurements is more than 0.001 inch (0.025
12. Install a capscrew (3) and lockwasher (4) in two holes
mm), the motor must be replaced. Using the same proce-
which are 180 degrees apart. Tighten the nuts to 125 foot-
dure, measure the journal on the other side of the gear.
pounds (17.3 m-kg).
13. Attach a torque wrench to the drive shaft and rotate
REASSEMBLY. To reassemble a motor which has been
the shaft. The shaft will be tight, but should turn with a
completely disassembled, including the bearings, proceed as
maximum of 5 to 10 foot-pounds of torque (0.69-1.38
m-kg). If the shaft will not turn with 5 to 10 foot-pounds
1. Place body (24) on a clean workbench with the large
(0.69-1.38 m-kg) of torque, the motor should be disas-
opening up and the mark made in step 7 of disassembly
sembled, inspected, and the problem corrected before
2. Lubricate the inside of body (24) with clean hydraulic
14. If the shaft turns properly, install the remaining cap
oil. Install O-rings (21) and back-up rings (20) on the
screws (3) and lockwashers (4). Tighten the capscrews to
125 foot-pounds (17.3 m-kg).
Two different types of isolation plates are used in this
motor. Close examination of the plates will show that
This hydraulic motor is a two-speed, fixed displacement,
two plates (item 7) have square edges and two plates
gear type motor, which consists of two independent motors
(item 18) have rounded edges.
connected by internal valving that directs the flow of oil to
only the rear section of the motor or to both sections of
the motor. The operation of the motor is as follows:
3. Install isolation plates (18) so that rounded edge enters
the body first.
When the motor is operated in the high speed mode, the
pilot port is blocked by the energized solenoid valve. The
4. Install center separator (23), end separators (22), and
shifter pistons in the motor remain in the block position
sealing strips (19) in the bottom of the body.
because, with no oil flow out the pilot port, the pressure at
5. Lubricate pressure plate (17) with clean hydraulic oil
each end of the shifter pistons is equal. The spring force
and place the pressure plate, bronze side up, in the opening
then shifts the pistons to the blocked position. All flow to
of the body as level as possible. Carefully slide the pressure
the motor is therefore directed through the rear motor
plate to the bottom of the body. Do not force the plate
section only, resulting in high RPM and lower torque.
Shifting the motor to lower range, by de-energizing the
solenoid valve, connects the pilot port to tank. A portion of
6. Install gear (16) in the bore nearest you. Do not drop
the flow going to the motor then passes through the
the gear into place, as this will damage the bronze on the
restrictor and the check valve, and then through the speed
pressure plate. Install gear (15) with the long journal up in
control valve to tank. Because of the oil flow, a pressure
the opposite bore.
drop occurs across the restrictor. The pressure applied to
7. Lubricate pressure plate (14) with clean hydraulic oil
the piston at the end containing the spring will now be less
and place it, bronze side down, over the protruding end of
than the pressure applied to the opposite end of the piston.
the gears and into the opening. Carefully slide the pressure
The piston will then shift toward the spring end, opening a
plate into the body.
passage for flow to the front motor section. The shifter
piston connected in the discharge port of the front motor
8. Install steel rings (13) so that the large diameter end
section is initially blocked when the other piston shifts to
enters the pressure plate first. Install O-rings (10) on the
the open position. Pressure builds up quickly in the dis-
steel rings. Be sure the O-rings are seated against the pres-
charge port of the front motor section, however, and this
sure plate, and then install back-up rings (9).
pressure is applied to the piston end connected in that port.
The piston shifts when the applied pressure is sufficient to
9. Install isolation plates (7), center separator (12), end
separators (11), and sealing strips (8).
overcome the spring force at the opposite end of the piston,