JLG G12-55A Service Manual - Manual (Page 101)

6-9 G10-55A, G12-55A
Transmission
6.7 TROUBLESHOOTING
This section provides an easy reference guide covering
the most common problems that may occur during
operation of the transmission.
Note: Contact local distributor if internal transmission
repair is required during the warranty period.
The transmission should be checked, serviced and
repaired only by experienced service technicians who
are aware of all safety instructions and particular
component features
Problem Cause Remedy
1. Transmission will
not engage or will
not shift properly.
1. Oil level too high or low. 1. Fill transmission to correct level with
hydraulic oil. Refer to Section Note:,
“Friction Modifier required for axle
differentials, see Section 2.5.3,
“Capacities.”.”
2. Transmission control lever not
functioning properly and/or a fault in
the wiring harness.Transmission
control lever not functioning properly
and/or a fault in the wiring harness.
2. Refer to Section 9.5, “Electrical System
Schematics.”
3. Transmission valve body solenoids
not functioning properly.
3. Refer to Section 9.5, “Electrical System
Schematics.”
4. Pilot-operated shift valves not
operating properly.
4. Clean the valve spool and housing.
Replace return spring as needed.
5. Pump output pressure low. 5. Refer to Problem 2. “Low or no pump
flow or pressure.”
6. Clutch piston o-rings damaged. 6. Replace o-rings.
7. Clutch discs worn or damaged. 7. Replace clutch discs.
8. Coupling shafts or gear
teeth damaged.
8. Replace couplings.
2. Low or no pump
flow or pressure.
1. Low oil level. 1. Fill transmission to correct level with
hydraulic oil. Refer to Section Note:,
“Friction Modifier required for axle
differentials, see Section 2.5.3,
“Capacities.”.”
2. Transmission filled with incorrect oil,
or oil contaminated.
2. Drain transmission and fill to correct
level with hydraulic oil. Refer to Section
Note:, “Friction Modifier required for axle
differentials, see Section 2.5.3,
“Capacities.”.”
3. Pump suction pipe screen clogged. 3. Clean, repair and/or replace
suction pipe.
4. Central shaft damaged. 4. Replace central shaft.
5. Pump worn or damaged. 5. Repair or replace pump assembly.