Manual Transmission Troubleshooting

Noisy in neutral with engine running:

1. Input shaft bearing worn.
2. Damaged main drive gear bearing.
3. Worn countershaft bearings.
4. Worn or damaged countershaft endplay shims.

Noisy in all gears:

1. Any of the above causes, and/or:
2. Insufficient lubricant

Noisy in one particular gear:

1. Worn, damaged or chipped gear teeth for that particular gear.
2. Worn or damaged synchronizer for that particular gear.

Slips out of high gear:

1. Transmission loose on clutch housing.
2. Dirt between the transmission case and engine or misalignment of the transmission

Difficulty in engaging gears:

1. Clutch not releasing completely
2. Loose, damaged or out-of-adjustment shift linkage. Make a thorough inspection, replacing parts as necessary
3. Leak or air in hydraulic system.

Oil leakage:

1. Excessive amount of lubricant in the transmission. Drain lubricant as required.
2. Driveaxle oil seal or speedometer oil seal in need of replacement
3. Shift rail plugs leaking

Clutch fails to release:

1. Leak in the clutch hydraulic system. Check the master cylinder, slave cylinder and lines
2. Clutch plate warped or damaged

Clutch slips:

1. Clutch plate oil soaked or lining worn. Remove clutch and inspect.
2. Clutch plate not seated. It may take 30 or 40 normal starts for a new one to seat.
3. Pressure plate worn
4. If clutch components are new, were was the pressure plate cleaned with lacquer thinner?

Clutch chatters during engagement:

1. Oil on clutch plate lining. Remove and inspect. Correct any leakage source.
2. Worn or loose engine or transmission mounts. These units move slightly when the clutch is released. Inspect the mounts and bolts
3. Worn splines on clutch plate hub. Remove the clutch components and inspect.
4. Warped pressure plate or flywheel. Remove the clutch components and inspect.
5. If clutch components are new, were was the pressure plate cleaned with lacquer thinner?

Squeal or rumble when clutch is fully engaged:

1. Release bearing binding on transmission bearing retainer. Remove clutch components and check bearing. Remove any burrs or nicks; clean and re-lubricate bearing retainer before installing.
2. If clutch components are new, were was the pressure plate cleaned with lacquer thinner?

Squeal or rumble when clutch is fully disengaged:

1. Worn, defective or broken release bearing
2. Worn or broken pressure plate springs (or diaphragm fingers)
3. If clutch components are new, were was the pressure plate cleaned with lacquer thinner?

Clutch pedal stays on floor when disengaged:

1. Linkage or release bearing binding. Inspect the linkage or remove the clutch components as necessary.
2. Make sure proper pedal stop (bumper) is installed.