Symptom Chart — Transmission, Manual

SYMPTOM CHART — TRANSMISSION, MANUAL

Condition	Possible Source	Action
Transmission Shifts Hard	Clutch does not completely release.	CHECK input shaft splines for lubrication and make sure the splines are not damaged.
	Transmission oil low or improper type.	ADD lubricant or CHANGE lubricant as required.
	Worn or damaged internal shift mechanism.	REMOVE transmission cover. CHECK internal shift mechanism by shifting into and out of all gears. REPAIR or REPLACE as required.
	Binding of sliding gears and/or synchronizers.	CHECK for free movement of gears and synchronizers. REPAIR or REPLACE as required.
	Housings and/or shafts out of alignment.	REMOVE transmission and CHECK for binding condition between input shaft and engine crankshaft pilot bearing or bushing. CHECK flywheel housing alignment. REPAIR or REPLACE as required.
Noisy in Forward Gears NOTE: While verifying the condition, determine whether the noise is gear rollover noise, release bearing rub or some other transmission-related noise. Gear rollover noise, inherent in manual transmissions, is caused by the constant mesh gears turning at engine idle speed, while the clutch is engaged and the transmission is in neutral; and release bearing rub is sometimes mistaken for mainshaft bearing noise. Gear rollover noise will disappear when the clutch is disengaged or when the transmission is engaged in gear. Release bearing rub will disappear when the clutch is engaged. In the event that a bearing is damaged, the noise is more pronounced while engaged in gear under load or coast than in neutral.	Lubricant level low or improper type.	ADD lubricant, or REFILL with specified lubricant.
	Components grinding on transmission.	CHECK for screws, bolts, etc., of cab or other components grounding out. CORRECT as required.
	Component housing bolts loose.	CHECK torque on transmission-to-flywheel housing bolts, output shaft flange nut and flywheel housing-to-engine block bolts. TIGHTEN bolts to specification.
	Flywheel housing-to-engine crankshaft alignment.	CHECK and ALIGN flywheel housing to engine crankshaft.
	Noisy bearings or gears.	REMOVE and DISASSEMBLE transmission. INSPECT input, output and countershaft bearings. INSPECT speedometer gear and gear teeth for wear or damage. REPLACE as required.
Gears Clash When Shifting from One Forward Gear to Another	Clutch not releasing completely.	CHECK clutch system. REFER to Group 08.
	Pilot bearing binding.	REMOVE transmission and CHECK for a binding condition between input shaft and engine crankshaft pilot bearing. REPLACE as required.
	Damaged gear teeth and/or synchronizer.	DISASSEMBLE transmission, REPAIR or REPLACE as required.
	Engine idle speed too high.	REFER to the Powertrain Control/Emissions Diagnosis Manual OBDII.
Transmission Jumps Out of Gear	Stiff gearshift lever boot. Improper fit of inner boot.	REPLACE gearshift lever boot if exceptionally stiff.
	Loose transmission-to-engine mounting bolts, or loose levers.	TIGHTEN transmission-to-engine block bolts to specifications. LOOSEN all bolts and RESEAT flywheel housing. TIGHTEN all bolts. TIGHTEN levers if necessary.
	Flywheel housing-to-engine crankshaft alignment out of line.	SHIM or REPLACE housing as required.
	Crankshaft pilot bearing worn.	REPLACE bearing.
	Interior components damage.	DISASSEMBLE transmission. INSPECT the synchronizer sleeves for free movement on their hubs. INSPECT the synchronizer blocking rings for widened index slots, rounded clutch teeth and smooth internal surface. CHECK countershaft cluster gear for excessive end play. CHECK shift forks for worn or loose mounting on shift rails. CHECK fork pads for excessive wear. INSPECT synchronizer sliding sleeve and gear clutch teeth for wear or damage. REPAIR or REPLACE as required.
	Worn gear teeth due to partial engagement.	REPLACE worn or damaged gears.
Transmission Will Not Shift into One Gear — All Others OK	Manual-shift linkage damaged or worn.	REPAIR or REPLACE parts as required.
	Backup switch ball frozen.	If reverse is problem, CHECK backup switch for ball frozen in extended position (if so equipped).
	Internal components.	REMOVE transmission. INSPECT shift rail and fork system, synchronizer system and gear clutch teeth for restricted travel. REPAIR or REPLACE as required.
Transmission is Locked in One Gear. It Cannot Be Shifted Out of That Gear	Internal components.	REMOVE transmission. INSPECT problem gears, shift rails and forks and synchronizer for wear or damage. REPAIR as required.
	Loose fork on rail.	CHECK shift rail interlock system.
Noise from Transfer Case	Incorrect tire inflation pressures and/or incorrect size tires and wheels.	MAKE sure that all tires and wheels are the same size, and that inflation pressures are correct.
	Excessive tire tread wear.	CHECK tire tread wear to see if there is more than .06 inch difference in tread wear between front and rear. INTERCHANGE one front and one rear wheel. REINFLATE tires to specifications.
	Internal components.	OPERATE vehicle in all transmission gears with transfer case in 2HI, or HI range. If there is noise in transmission in neutral gear, or in some gears and not in others, REMOVE and REPAIR transmission. If there is noise in all gears, OPERATE vehicle in all transfer case ranges. If noisy in all ranges or HI range only, DISASSEMBLE transfer case. CHECK input gear, intermediate and front output shaft gear for damage. REPLACE as required. If noisy in LO range only, INSPECT intermediate gear and sliding gears for damage. REPLACE as required.
4-Wheel Drive Transfer Case Jumps Out of Gear	Incomplete shift linkage travel.	ADJUST linkage to provide complete gear engagement.
	Loose mounting bolts.	TIGHTEN mounting bolts.
	Front and rear driveshaft slip-yokes dry or loose.	LUBRICATE and REPAIR slip-yokes as required. TIGHTEN flange yoke attaching nut to specifications.
	Internal components.	DISASSEMBLE transfer case. INSPECT sliding clutch hub and gear clutch teeth for damage. REPLACE as required.
Transmission Leaks	Improper amount of lubricant— wrong type.	CHECK level and type. FILL to bottom of filler plug hole.
	Other component leaking.	IDENTIFY leaking fluid as engine, power steering or transmission fluid. REPAIR as required.
	False report.	REMOVE all traces of lube on exposed transmission surfaces. CHECK vent for free breathing. OPERATE transmission and INSPECT for new leakage. REPAIR as required.
	Internal components.	REMOVE transmission. INSPECT for leaks at the input shaft bearing retainer seal and shift rail expansion plug. INSPECT for leaks at the top cover gasket. INSPECT case for sand holes or cracks. REPAIR or REPLACE as required.
	Improper installation torque on fill and drain plugs.	CHECK fill, drain plug and bore threads. REPAIR as necessary. TIGHTEN to specified torque value.
No Power Transmitted, Transmission Seems to Shift Through Gear in 4x4 Only	Transfer case in neutral position.	REFER to Diagnosis and Testing in Section 07-07.
	Internal transmission damage.	REMOVE transmission and INSPECT.

DIAGNOSIS GUIDE — BEARING FAILURE CONCERNS

Condition	Possible Source	Action
The Service Life of Most Transmissions Is Governed by the Life of the Bearings. The Majority of Bearing Failures Can Be Related to Vibration or Contamination of the Fluid. Some of the Biggest Reasons for Bearing Failures Are:	Worn out due to other part failure.	REMOVE, DISASSEMBLE and CLEAN the transmission, then REPLACE damaged parts. (Necessary to RESET bearing preload if any tapered bearings are replaced.)
	Damage due to towing vehicle further than 50 miles with driveshaft installed. Mainshaft tapered bearing and needle caged bearings are especially susceptible to damage.	Same as above. PROVIDE correct towing procedures to tow operator.
	Fatigue of raceways or rollers.	Same as above.
	Wrong type or grade of lubricant.	Same as above.
	Lack of lubricant.	Same as above.
	Vibrations break-up of retainer and brinelling of races.	DETERMINE cause of vibration and CORRECT. Otherwise PROCEED as above.
	Bearings tied up due to chips in bearings.	Same as above. REPLACE damaged parts.
	Bearing set up too tight or too loose.	Same as above.
	Improper fit of shafts or bore.	Same as above. REPLACE any shafts or housing section with improper fit.
	Acid etch of bearing due to water in lube.	Same as above. IDENTIFY and CORRECT source of water entry.
	Overloading of vehicle.	Same as above. COMPARE gross combined weight of vehicle and trailer to rated capacity.
	Incorrect preload causes faster wearing of the bearings, due to incomplete contact area.	Same as above. Be sure to FOLLOW preload setting procedure in this Manual.
	Pocket bearing not lubricated due to missing, damaged or misinstalled input shaft oil dam.	REPLACE damaged components and make sure of proper oil dam installation. REFER to the appropriate transmission section in this group. CHECK for proper installation of the snap ring on the mainshaft next to the oil dam.
	Pocket bearing not lubricated due to damaged oil baffle in the input bearing shim pack.	REPLACE damaged components making sure the oil baffle is not damaged during reassembly.