HYDROSTATIC POWER TRAIN
4203780 First Edition 5-27
5
Hydrostatic System Operating Hot
Excessive Traction Pump Noise
Differential Lock Will Not Engage
Differential Lock Will Not Disengage
Probable Cause Remedy
Hydraulic oil not at correct level in reservoir. Fill reservoir to correct level. (Refer to “Safety, Operation, and
Maintenance Manual” for the correct oil specifications.)
Tow valve open. Close tow valve. (Refer to “Safety, Operation, and Maintenance
Manual.”)
Oil cooler has dirt or debris in fins. Clean oil cooler fins of dirt and debris.
Incorrect charge pressure relief setting. Test charge pressure relief valve setting. (See “Charge Pressure
Test” on page 5-34.) Repair or replace charge pressure relief
valve as needed. (See “Control Valve” on page 5-55.)
Slippage in pump or motor. Perform instrument tests. (See “Instrument Test Overview” on
page 5-34.)
Faulty relief valve. Test and repair. (See “Traction Pump Tests” on page 5-40.)
Probable Cause Remedy
Hydraulic oil not at correct level in reservoir. Fill reservoir to correct level. (Refer to “Safety, Operation, and
Maintenance Manual” for the correct oil specifications.)
Hydraulic oil cold. Warm hydraulic oil to operating temperature.
Air in hydraulic system (air bubbles in hydraulic oil). Check suction line for air leaks. Repair as needed. Operate
various hydraulic systems until hydraulic system is free of air.
Traction pump worn or damaged. Repair or replace pump as needed. (See “Traction Pump” on
page 5-50.)
Probable Cause Remedy
Differential lock solenoid does not engage when differential lock
switch is depressed.
Problem in electrical circuit. (See Electrical section,
Troubleshooting—“Four Wheel Drive Circuit Schematic” on
page 4-41.)
Differential lock valve in control valve assembly sticking. Repair or replace differential lock valve. (See “Control Valve” on
page 5-55.)
Low charge pressure. Test charge pressure relief valve setting. (See “Charge Pressure
Test” on page 5-34.) Repair or replace charge pressure relief
valve as needed. (See “Control Valve” on page 5-55.)
Differential lock assembly damaged. Repair differential lock assembly. (See “Differential Lock
Assembly” on page 5-64.)
Probable Cause Remedy
Differential lock solenoid does not disengage when differential
lock switch is released.
Problem in electrical circuit. (See Electrical section,
Troubleshooting—“Four Wheel Drive Circuit Schematic” on
page 4-41.)
Differential lock valve in control valve assembly sticking. Repair or replace differential lock valve. (See “Control Valve” on
page 5-55.)
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