Drive Shaft Noises

When operating a vehicle to verify a complaint. keep in mind that other components could be at fault. A worn wheel bearing, squeaking spring, defective tire. transmission, or differential troubles could be at fault. You must use your knowledge of each system to detect which component is causing the trouble.

Drive shaft noises are usually caused by worn U- joints, slip joint wear, or a faulty center support bearing. Drive shaft noises and possible causes are as follows:

Grinding and squeaking from the drive shaft is frequently caused by worn universal joints. The joints become dry, causing the rollers to wear. The unlubricated, damaged rollers then produce a grinding or squeaking sound, as they operate on the scored cap and cross surfaces.

A clunking sound, when going from acceleration to deceleration or deceleration to acceleration, may be caused by slip yoke problems. The splines may be worn. The yoke transmission extension housing bushing may also be worn. This will let the yoke move up and down with changes in drive line torque. An excessively worn U-joint or differential problem can also cause a similar noise.

A whining sound from the drive shaft is sometimes caused by a dry, worn center support bearing. Since this bearing makes complete revolutions. it will make a different sound than a bad universal joint. A high pitched. more constant, whine will usually come from a faulty center support bearing.

Any other abnormal sound should be traced using your knowledge of mechanics. a stethoscope, and the vehicles service manual troubleshooting chart.

Drive Shaft Inspection

To inspect the drive shaft for wear or damage, raise the vehicle and place it on jack stands. Look for undercoating or mud on the drive shaft. Check for missing balance weights, cracked welds, and other drive shaft problems.

To check for working U-joints, wiggle and rotate each U-joint back and forth. Watch the universal joint carefully. Try to detect any play between the cross and the yoke. If the cross moves inside the yoke, the U-joint is worn and needs to be replaced.

Also, wiggle the slip yoke up and down. If it moves in the transmission bushing excessively, either the 5-8 yoke or the bushing is worn. Inspect the rear yoke bolts for tightness. Make sure the rear motor mount is NOT broken. Look at any condition that can upset the operation of the drive shaft.

If after a thorough check of the drive shaft you fail to determine the problem, notify the shop supervisor. The drive shaft may require detailed measuring (drive shaft runout and drive shaft angle) or have its balance checked.

Universal Joint Service

The universal joints on many automotive vehicles are factory lubricated. However, construc- tion equipment have universal joints that have lubrication fittings that should be lubricated at regular intervals.

Service to universal joints that are factory lubricated is limited to replacement when signs of excessive wear are present. The universal joints provided with lubrication fittings are only lubricated with a hand operated low-pressure grease guns. Use of a high-pressure grease gun will damage the seals, resulting in early failure of the universal joint.

Another area to be concerned with when servicing the universal joints is the slip yoke (joint). Slip yokes may be lubricated from the transmission or lubricated through a lubrication fitting.

NOTE

Always consult the manufacturer's service manual for lubrication intervals and proper lubricants to be used.

A worn universal joint is the most common drive line problem, causing squeaking, grinding, clunking, or clicking sounds. The grease inside the joint can dry out. The roller bearings will wear small indentations in the cross. When the bearings try to roll over these dents, a loud metal-on-metal grinding or chirp sound can result.

Quite often, a worn U-joint is discovered when the transmission is placed in REVERSE. When the vehicle is backed up, the roller bearing is forced over the wear indentation against normal rotation. When this occurs, the rollers will catch on the sharp edges in the worn joint, causing even a louder sound.

UNIVERSAL JOINT DISASSEMBLY. - The universal joint may require removal and disassembly to enable you to check the condition of the joint