Copyright by Goodheart-Willcox Co., Inc.
290 Manual Drive Trains and Axles
Damaged
circlips
Missing
boot clamps
Damaged or
worn boot
Scored or pitted
CV joint balls
Inside of CV
joint housing worn
Damaged
axle shaft
Loss of CV
joint lubricant
Worn, dry
bearing
Stripped
nut or
spindle
threads
Figure 15-1. Study the common CV axle problems.
(Champion Parts)
Introduction
The importance of CV axle diagnosis and repair has
grown as the number of front-wheel drive vehicles on the
road has increased. This chapter explains the proper ways
to diagnose and service CV axle assemblies.
Chapter 14 contained information on the construction
and operation of CV axles. If you encounter a term or con-
cept in this chapter that you do not understand, review the
material in Chapter 14.
CV Axle Problems and
Troubleshooting
Although the CV axle is a relatively simple device, it
is subject to several problems. See Figure 15-1. CV axle
problems can be grouped into three general categories:
noises, vibrations, and lubricant leaks. Before deciding a
CV axle is defective, make sure the problem is not caused
by a defect in the engine, transaxle, brakes, steering and
suspension components, wheels, or tires. Since these com-
ponents are generally located in the front of the vehicle, it
is easy to mistake sounds from these components for CV
axle noises.
Abnormal Noise
Abnormal noises in the CV axles are unusual sounds,
such as clunking, popping, or clicking noises that are
caused by defective CV axle components. Most CV axle
noises occur when the wheels are turned or the brakes are
applied. Dry or worn front wheel bearings, on the other
hand, generally produce rumbling or roaring noises that
vary with vehicle speed.
One of the most common causes of CV axle noise is
a lack of lubricant in a CV joint. Lubricant may dry out
after extensive use, or it may leak out through a damaged
boot. A dry CV joint usually makes a popping, clicking, or
snapping sound. Sometimes, regreasing the joint will solve
the problem. Often, however, the joint will be worn or
rusted and must be replaced or rebuilt.
Another cause of CV axle noise is a worn CV joint.
Wear can occur at any point where the CV joint compo-
nents move in relation to each other. Worn parts generally
cause the joint to clunk or knock when the vehicle is
turned or the brakes are applied. In some cases, the
suspension attaching bolts or the axle bolts become loose,
allowing movement between parts.
It is sometimes difficult to determine which joint in a
CV axle assembly is defective. It may be possible to see
excess movement between parts on either side of a defec-
tive CV joint. To check for movement, raise the vehicle. If
the vehicle has an automatic transaxle, put it in park. If the
vehicle has a manual transaxle, it can be placed in any
gear. Try to turn the wheel on the problem axle with your
hand and observe the axle shafts on both sides of the sus-
pected CV joint. Excess movement indicates a worn or
damaged joint. It may help to compare movement around
the joints on both sides of the vehicle. If one joint is looser
than the others, it is probably defective.
Repairing a noisy CV axle can be as simple as tighten-
ing loose bolts. At the other extreme, a noisy CV axle could
mean that a complete rebuild of the CV joints is necessary.
CV Axle Vibration
CV axle vibrations are pulsations or other cyclical
shocks caused by worn or damaged CV axle parts.
Vibrations may be caused by a bent or twisted axle shaft,
worn CV joints or wheel bearings, or loose attaching bolts.
Always check for worn or loose parts when vibrations are
evident. If a bent CV axle shaft is suspected, it may be
necessary to check the runout of the shaft.
Most vibrations will be felt through the steering wheel
and, in some cases, the vehicle body. The frequency of CV
axle vibrations will increase as vehicle speed increases.
Since the CV axles are commonly used at the front of a
vehicle, even slight vibrations will be noticeable. The usual
cure for CV axle vibrations is the replacement of defective
components.
Lubricant Leakage
CV axle lubricant leakage generally originates from
the CV joints or the wheel bearings. Most CV joint leaks
are caused by torn boots or loose boot clamps. Wheel
bearing lubricant will leak from a defective bearing seal.
In some cases, transaxle fluid will leak from a defective
seal between the transaxle housing and the CV axle
shaft.