JLG 450A_AJ Series II Service Manual - Manual (Page 96)

SECTION 3 - CHASSIS & TURNTABLE
3-46 – JLG Lift – 3121180
Assembly
1. Use filtered system oil to lubricate all critical moving
parts before assembly.
2. Install one snap ring (4) in rear groove of drive shaft (7
or 25). Install one thrust washer (5), thrust bearing (6),
and second thrust washer (5) on drive shaft (7 or 25).
Install second snap ring (4) in front groove on drive
shaft.
3. Replace needle bearing (8) in housing (9) if neces-
sary. Install shaft in housing assembly (9) and install
washer (3). Oil I.D. of new shaft seal (2) and press
into position. Retain with snap ring (1).
4. Compress pin keeper (15) and install in spline area
of piston block (14).
5. Install three pins (16) in special grooves of spline
with head end of pin toward inside of block.
6. Install washer (17), spring (18), and second washer
(17). Use two 3/8" I.D. washers and 3/8" x 3-1/4" cap
screw to compress spring. Retain with snap ring (19).
Remove 3/8" x 3-1/4" cap screw and two washers.
7. Install pivot (13), spider (12), and piston assemblies (11)
in piston block assembly.
8. Lubricate thrust race (10) and install in housing
assembly.
9. Install piston block assembly in housing assembly.
The piston shoes must contact the thrust race (10).
Be sure all parts are in their proper position.
10. Install new needle bearing (20) in back plate (22 or 27)
if necessary.
11. Install new O-ring (21) on back plate (22 or 27).
12. Install back plate (22 or 27) on housing.
13. Install six cap screws (23 or 28 & 29) and torque to
15 to 18 ft-lb (21 to 25 Nm).
14. On through shaft type assembly, install shaft seal (30)
and snap ring (31) in back plate (27). Install key (26)
in drive shaft (25).
Drive Motor Troubleshooting
Pump must be isolated from motor to determine which
unit is actually malfunctioning. A worn pump or worn
motor give the same indication. It is advisable to first run a
pressure and flow check on the pump to make sure it is
performing within operating specifications. The following
trouble shooting suggestions are based on assumptions
pump has been flow and pressure checked and is within
operating specifications.
Table 3-2. Motor Trouble Shooting
Possible Trouble Cause Remedies
Motor turns while unloaded but
slows down or stops when load is
applied A. Soored back plate.
B. Scored or worn piston shoes.
C. Low relief valve pressure.
A. Remove back plate and examine surface condition of flat area; if scored, replace
back plate.
Do not lap
B. Disassemble motor, examine condition of shoes on pistons as a complete set if
necessary.
Do not lap.
C. Check relief valve for proper pressure setting; adjust or replace relief valve.
Motor will not turn. A. Severely scored back plate. A. Disassemble motor completely. Inspect all parts, replace all worn parts, Clean
all parts, replace all worn parts and flush hydraulic system.
Motor free wheels. A. Oil flow and pressure shut off
going to motor. When the hydraulic system is shut off, either by shutting off the engine on a closed
loop system or returning the control valve spool to neutral on a open center system,
the motor will free wheel after it has leaked off. This is inherent in the design. On a
closed loop or propulsion system, the motor will not free wheel as long as charge
pressure is maintained to and from the motor.
Excessive case drain flow. A. Excessive internal wear in motor. Disassemble motor, inspect parts and replace as necessary. Case drain flow
should not exceed 1.5 GPM at full pressure.