ASE G1 Auto Maintenance and Light RepairManual Drive Train and AxlesMedium
A vehicle with a manual transmission exhibits difficulty shifting into any gear when the engine is running, but shifts smoothly when the engine is off. The clutch pedal feels normal and has proper free play. Which of the following is the MOST likely cause?
- AA seized pilot bearing
- BA damaged pressure plate diaphragm spring
- CAir in the hydraulic clutch system
- DA worn clutch disc facing
Show answer & explanationAnswer & explanation
Correct answer: C. Air in the hydraulic clutch system
Difficulty shifting when the engine is running but easy shifting when off strongly suggests the clutch is not fully disengaging. If the pedal feels normal and free play is correct, air in the hydraulic system is a common cause, as it prevents full pressure transfer to the release bearing.
Why the other options are wrong
- A. A seized pilot bearing would cause noise, especially with the clutch disengaged, and potentially make shifting difficult, but usually with a noticeable change in pedal feel or noise.
- B. A damaged pressure plate diaphragm spring would affect clutch engagement/disengagement and often impact pedal feel or cause chatter, but 'normal' pedal feel points elsewhere.
- D. A worn clutch disc would cause slippage, not difficulty disengaging.
Clutch Disengagement Failure
A condition where the clutch disc remains partially engaged even when the clutch pedal is fully depressed, leading to difficulty shifting gears, especially with the engine running.
- Symptoms: hard shifting, grinding gears when engine is running.
- Clutch feels 'draggy' or 'sticky'.
- Can be caused by air in hydraulics, bent fork, worn master/slave cylinder.
Memory trick: Engine on, gears won't go? Clutch isn't letting go!