Mustang Manual Transmission Problemsby John Stevens J.D.
Although the Mustang's transmission is generally regarded as quite durable, given enough time it will eventually develop problems. Many problems associated with the Mustang's transmission can be repaired without having to completely rebuild it, but before any repair can be performed, the problem must first be identified.
Transmission Jumps Out of Gear
There are several possible reasons why the Mustang's manual transmission unexpectedly jumps out of gear. Perhaps the most common cause is due to the misalignment of the transmission's case or clutch housing. A worn pilot bearing at the rear of the crankshaft can also be the culprit, as can a bent transmission shaft. A relatively minor problem that can cause the transmission to jump out of gear is an improper spring tension on the shifter's rail, while the most serious cause is worn teeth gears within the transmission.
Transmission Sticks in Gear
If the transmission sticks in gear, it could be due to the clutch not fully releasing, or because the teeth on the clutch shaft are damaged. A gear shifter that sticks in its boot can also cause the problem, in which case the repair must be made at the boot rather than the transmission. The most serious cause of clutch sticking is corroded internal transmission components. Finally, a lack of lubrication can cause the transmission to stick.
Transmission Gears will not Synchronize
Synchronization refers to the process by which the gears within the transmission rotate together. A transmission which is not synchronized will make it difficult to change gears, since the gears within the transmission are not properly aligned. If it is only difficult to change higher gears, the problem likely lies with a binding pilot bearing on the transmission's mainshaft. If it is difficult to change to any gear, the problem might simply be caused by a clutch that does not fully release, a weak or broken detent spring, or a lack of lubrication. The most serious cause is badly worn gear teeth.
Noise Emanating from Transmission
When a Mustang's manual transmission makes noise, chances are good that the noise is being produced by a worn bearing. Identifying the damaged bearing can often be determined by noting which gear(s) the noise is produced. If the transmission is noisy in one gear only, the reverse countergear is likely the cause. If the noise is produced only in reverse, either the reverse gear or the countergear is probably damaged. If the transmission is noisy only in neutral, the main drive gear bearing or the countergear bearings are likely the problem. If the noise is produced in all gears, the transmission may just need lubrication, or the main gear, countergear, or mainshaft bearings could be damaged.
A slipping clutch is usually due to a lack of lubrication at either the clutch linkage or at the clutch cable itself. The lack of lubrication causes the linkage or cable to bind, which in turn causes the gear engagement problem. If the linkage and cable are lubricated, the linkage may simply require adjustment. More serious causes include a broken or weak pressure plate spring, or grease on the drive plates within the transmission.