Manual Transmission/Transaxle: Testing and Inspection
COMMON PROBLEM CAUSESThe majority of transmission malfunctions are a result of:
- insufficient lubricant.
- incorrect lubricant.
- misassembled or damaged internal components.
- improper operation.
HARD SHIFTING
A low lubricant level, loose or worn shift lever, or loose, damaged shift housing components are common causes of hard shifting. If hard shifting is also accompanied by gear clash, synchronizer clutch and stop rings, or mainshaft gear teeth may be worn or damaged. Hard shifting may also be caused by a loose, or misaligned shift cover, or alignment dowels. Worn, or damaged shift cover components will also cause hard shifting. Any of the foregoing faults will cause component bind and high shift efforts.
Misassembled synchro components will also cause shift problems. Incorrectly installed synchro sleeves, struts, or springs will all cause shift problems.
NOISY OPERATION
Transmission noise is most often a result of worn or damaged components. Chipped, broken gear or synchronizer teeth and brinnelled, spalled bearings all cause noise.
Abnormal wear and damage to internal components is frequently the end result of insufficient lubricant, non-recommended lubricants, or improper operation.
SLIPS OUT OF GEAR
Transmission disengagement may be caused by misaligned or damaged shift components, or worn teeth on the mainshaft gears or synchro components. Incorrect assembly will also contribute to gear disengagement.
LOW LUBRICANT LEVEL
Insufficient transmission lubricant is usually the result of leaks, or inaccurate fluid level check or refill method.
Leaks will be evident by the presence of gear oil around the leak point. If leakage is not evident, the condition is probably the result of an under fill condition.
If air powered lubrication equipment is used to fill a transmission, be sure the equipment is properly calibrated. Equipment out of calibration can lead to an underfill condition.
CLUTCH PROBLEMS
Worn, damaged, or misaligned clutch components can cause difficult shifting, gear clash and noise.
A damaged pilot bearing will cause noise. If bearing damage is severe, drive gear misalignment and hard shifting can also occur.
A worn or damaged clutch disc, pressure plate, or release bearing can cause hard shifting and gear clash.
Damaged or worn clutch hydraulic components, or leaks in the fluid lines or cylinders will cause hard shifting and gear clash. Failure of one of the clutch hydraulic cylinders can result in incomplete clutch release or engagement.
Verify that clutch components are all in good condition before removing the transmission for repair.