Overdrive Faults & Diagnosis

Overdrive Does Not Engage

• Insufficient oil level in the unit
• Solenoid not operating due to electrical system fault
• Solenoid operating lever out of adjustment
• Insufficient hydraulic pressure due to improper seating of the pump non-return valve (usually caused by dirt on the ball seat)
• Pump not working
• Filter blocked
• Inadequate hydraulic pressure due to sticking or worn relief valve
• Damaged internal parts requiring removal and overhaul of the unit

Overdrive Falls Out of Operation

• Inadequate oil pressure
• Incorrect adjustment
• Solenoid weak
• Open circuit in isolator switch
• Accumulator piston damage
• Defective relay
• Throttle switch is incorrectly adjusted
• Incorrect solenoid wiring
• Open circuit in relay winding

Overdrive Does Not Release – Do not engage reverse gear since damage may result

• Fault in the electrical control system
• Blocked restrictor jet in operating valve
• Solenoid operating lever out of adjustment
• Sticking cone clutch
• Damaged internal parts requiring removal and overhaul of the unit

Clutch Slip in Overdrive

• Insufficient oil level in the unit
• Solenoid operating level out of adjustment
• Insufficient hydraulic pressure due to improper seating of the pump non-return valve (usually caused by dirt on the ball seat)
• Filter blocked
• Inadequate hydraulic pressure due to sticking or worn relief valve

Clutch Slip in Reverse or Free-Wheel Condition on Overrun

• Solenoid operating lever out of adjustment
• Partially blocked restrictor jet in operating valve
• Worn clutch linings

Overdrive Engage Slowly

• Low oil pressure
• Accumulator piston damaged

Overdrive Does Not Engage Until Warm

• Incorrect oil

Noisy Operation

• Rear overdrive bearing is worn
• Annulus gears worn
  

Vehicle Will Not Back Up

• Overdrive stuck
• Restrictor hole plugged
• Magnet and filter screen missing