removal; however, if the case is misaligned because of dirt or other foreign material, it
may be possible to clean and realign it without removal.
Jumps out of gear.
When a transmission jumps out of gear, the shift lever "pops," or
moves into neutral during operation.
First, check the transmission linkage and shift lever arms. If the shift assembly is badly
worn, it should be rebuilt or replaced.
A worn clutch pilot bearing may also cause the transmission to jump out of gear. Severe
vibration, caused by the wobbling transmission input shaft, can wiggle and move the
shift forks and synchronizers.
Other problems inside the transmission can cause it to jump out of gear. They include
worn synchronizer inserts and springs, worn shift fork assemblies or shift rails, and wear
and excessive play in the countershaft and output shaft assemblies.
Locked in gear.
When the shifter is locked in one gear, check the transmission shifter
assembly and linkage. Look for bent shift rods, worn linkage, bushings, and shifter
arms. Also check linkage adjustment. With a shift rail mechanism, worn or damaged
rails, detents, or forks could be the cause.
A transmission can also become locked in gear when drive gear teeth are broken. The
teeth can jam together and be locked by bits of metal from chipped teeth.
Diagnosis chart.
Refer to the quick reference diagnosis chart (
Figure 8-2
).
8-7
NAVEDTRA
14050A