Manual Transmission Quick Reference Diagnosis Chart
Condition
Possible cause
Correction
Leaks lubricant
1.
Cover loose
2.
Cover gasket loose or defective
3.
Front bearing retainer loose, broken, or
gasket defective
4.
Front bearing retainer seal defective
5.
Output shaft seal worn
6.
Countershaft lose in case
7.
Lubricant level too high
8.
Shaft expansion plugs loose in case
9.
No sealer on bolt threads
10. Damaged shifter shaft seal
11. Vent plugged
12. Wrong lubricant
13. Cracked case or extension housing
14. Drain or filler plug loose
1.
Tighten cover
2.
Tighten cover and/or replace gasket
3.
Tighten retainer, replace gasket or retainer
4.
Replace seal
5.
Replace seal
6.
Replace case
7.
Drain to level of filler plug
8.
Replace plugs. Use sealer
9.
Seal threads
10. Replace seal
11. Open vent
12. Drain and refill with recommended lubricant
13. Replace case or housing
14. Tighten plug
Shifts hard
1.
Excessive clutch pedal free travel
2.
Worn or defective clutch
3.
Failure to fully depress clutch pedal when
shifting
4.
Shift cover loose
5.
Shift fork, shafts lever, or detents worn loose
6.
Improper shift linkage adjustment
7.
Linkage needs lubricant
8.
Linkage binding, bent, or loose
9.
Wrong transmission lubricant
10. Insufficient lubricant
11. Excess amount of lubricant
12. Transmission misaligned
13. Front bearing retainer loose or cracked
14. Synchronizer worn, damaged, or improperly
assembled
1.
Adjust free travel
2.
Replace worn parts
3.
Instruct driver
4.
Tighten cover
5.
Tighten or replace
6.
Adjust linkage
7.
Lubricate
8.
Free, straighten, or tighten as needed
9.
Drain and fill with recommended lubricant
10. Add lubricant to filler plug level
11. Drain to level of filler plug
12. Correct alignment
13. Tighten or replace retainer
14. Replace or reassemble synchronizer
Slips or jumps out of
gear
1.
Transmission loose or misaligned
2.
Clutch housing loose or misaligned
3.
Shift linkage improperly adjusted
4.
Shift rail detents worn or detent springs weak
5.
Synchronizer clutch sleeve teeth worn
6.
Loose shifter cover
7.
Shift fork, shaft, or levers worn
8.
Worn teeth on main drive gear or other gears
9.
Worn countershaft gear assembly bearings
and/or thrust washers
10. Worn reverse idler gear assembly bushing or
bearings
11. Worn output shaft pilot bearing
12. Front bearing retainer loose
13. Other parts striking shift linkage
14. Worn input or output shaft bearings
15. Worn input shaft bushing in flywheel
16. Bent output shaft
1.
Tighten and/or align
2.
Tighten and/or align
3.
Adjust linkage
4.
Replace detents and/or springs
5.
Replace synchronizer
6.
Tighten cover
7.
Replace worn part
8.
Replace input shaft or gears
9.
Replace countershaft gear bearings and
washings
10. Replace gear, bearings, and shaft
11. Replace rollers, replace shafts if necessary
12. Tighten retainer
13. Make adjustments to provide clearance
14. Replace bearings
15. Replacing bushing or bearing
16. Replace shaft
Gear clash during
downshifting
1.
Synchronizer worn, damaged, improperly
assembled
2.
Shifting too fast (ramming into lower gear)
3.
Shifting to a lower gear when road speed is
excessive
4.
Clutch not releasing properly
5.
Excessive output shaft endplay
1.
synchronizer
2.
Force into gear with a smooth, slower shift
3.
Slow down to appropriate speed before
shifting
4.
Adjust or repair as needed
5.
Adjust endplay
Gear clash shifting from
Neutral to Reverse
1.
Insufficient clutch pedal free travel
2.
Worn lubricant
3.
Engine rpm too high
4.
Driver not waiting long enough after
depressing clutch
5.
Sticking clutch pilot bearing
1.
Adjust free travel
2.
Drain and fill with correct lubricant
3.
Set to correct idle rpm
4.
Instruct driver
5.
Replace pilot bearing
Figure 8-2 - Transmission quick reference diagnosis chart.
8-8
NAVEDTRA
14050A