120H, 12H, 135H, 140H, 143H, 160H and 163H Motor Graders Caterpillar

Troubleshooting the Power Train

Problem: The transmission will not shift into any gear from the Neutral position

Probable Causes

• Low battery voltage

• Wiring harness connections

• Transmission control (lever)

• Electrical problem with the clutch pedal

• Main relief valve

• Transmission oil pump

• Rotating seal leakage in the transmission

Problem: The transmission has lost a single gear

Probable Causes

• The wiring harness for the transmission control

• Transmission control (lever)

• Electronic control module

Problem: The motor grader has lost multiple forward/reverse gear selections

Probable Causes

• Wiring harness

• Solenoids

• Transmission control (lever)

• Electronic control module

• Stations in the transmission control valve

• Internal transmission problem

Problem: The transmission slips

Probable Causes

• Low oil pressure

• Main relief valve

• Valve for the centershift lock

• Differential lock valve

• Low clutch pressure

• Solenoid

• Driver in the electronic control module

• Damage to the transmission control valve

• Contamination in the transmission control valve

• Rotating shaft seal

• Rotating shaft O-ring

• Worn clutch

• Mechanical problem

• The calibration of the clutch pedal

• Proportional solenoid valves

• Clutch piston seal

Problem: The motor grader creeps when the clutch pedal is fully depressed

Probable Causes

• Calibration for the clutch pedal

• Proportional solenoid valves

• Wiring harness for the proportional solenoid valves

• Contamination in the proportional solenoid valve

• Driver in the electronic control module

• Internal clutch drag

Problem: When the transmission shifts a hesitation occurs

Probable Causes

• Low initial pressures on speed clutches

• Low initial pressures on the clutches (range)

• Contamination in the transmission control valve

• Oil temperature sensor

• Modulation orifice

• Proportional solenoid valve

• Calibration of the proportional solenoid valve

• Drivers in the electronic control module

• Speed sensors

• Internal seal leakage on the transmission

• Internal pump leakage

• Main relief valve

• Valve for the centershift lock

• Differential lock valve

• The oil viscosity has been changed and the transmission control valve has not been recalibrated.

Problem: The transmission shifts are harsh

Probable Causes

• Transmission speed sensor

• Wiring harness for the transmission speed sensor

• Oil temperature sensor

• Proportional solenoid valve

• Calibration of the proportional solenoid valve

• Broken spring in the transmission control valve

• A spool in the transmission control valve sticks.

• The piston on a clutch sticks.

• The oil viscosity has been changed and the transmission control valve has not been recalibrated.

Problem: The transmission shifts are sluggish

Probable Causes

• Slow clutch disengagement

• The calibration of the clutch pedal

• The calibration of the proportional solenoid valve

• The parking brake drags.

Problem: The transmission shifts at the wrong point when the autoshift control is in the ON position

Probable Causes

• Transmission input speed sensor

• Transmission output speed sensor

• The electronic control module has the wrong transmission configuration code.

Problem: The transmission does not shift into all the gears when the autoshift is in the ON position

Probable Causes

• Transmission input speed sensor

• Transmission output speed sensor

• Transmission control

• Transmission control is positioned below the programmed lowest gear.

Problem: The transmission shifts into the wrong gear when the autoshift is in the ON position

Probable Causes

• Transmission input speed sensor

• Transmission output speed sensor