The Transmission / Differential FAQ

[Whizbang]

Troubleshooting (Manual Transmissions)

Q. Abnormal noise from transmission?
A. Probable causes:
1. Insufficient oil
2. Deterioration of oil quality
3. Worn bearing
4. Wear of sliding surfaces of counter-shaft gear
5. Wear of sliding surfaces of gears
6. Excessive gear backlash
7. Damaged gear teeth

Remedies corresponding to above:
1. Add oil
2. Replace oil
3. Adjust or replace
4. Replace
5. Replace
6. Replace
7. Replace


Q. Difficulty shifting?
A. Probable causes:
1. Bent change rod
2. No grease in transmission control system
3. Insufficient oil
4. Deterioration of oil quality
5. Wear or play of shift fork / rod
6. Wear or poor contact of synchro ring or synchro cone of gear
7. Excessive play in gears
8. Wear of bearing
9. Wear of synchro key
10. Improper disengagement of clutch

Remedies corresponding to above:
1. Replace
2. Add grease
3. Add oil
4. Replace oil
5. Replace
6. Replace
7. Replace
8. Adjust or replace
9. Replace
10. Improper disengagement of clutch


Q. Jump out of gear?
A. Probable causes:
1. Bent change rod
2. Weak / broken lock-ball spring
3. Wear of shift fork
4. Wear of clutch hub or hub sleeve
5. Wear of gear sliding parts
6. Excessive gear backlash
7. Wear of bearing
8. Loose or broken engine / transmission mounts

Remedies corresponding to above:
1. Replace
2. Replace
3. Replace
4. Replace
5. Replace
6. Replace
7. Adjust or replace
8. Fix / Tighten


Q. Gear shift lever difficult / rough?
A. Probable causes:
1. Sticking control rod
2. Malfunction of ball joint on control rod
3. Bent change rod

Remedies corresponding to above:
1. Replace
2. Replace
3. Replace