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19th Annual Technical Forum: CV Halfshafts


8/10/2011
By Larry Carley

Is it easier to replace a worn constant velocity joint, or to replace the entire halfshaft?
 

A. The hands down favorite in most instances is to replace the entire halfshaft as a complete assembly. Why? It’s faster, easier and only a little more expensive than replacing a bad CV joint.

Labor is the most expensive part of this job. Replacing a CV joint or an entire halfshaft assembly requires removing the halfshaft from the vehicle.

The halfshafts in front-wheel drive cars and minivans connect the transaxle to front-drive wheels. On all-wheel drive (AWD) or rear-wheel drive (RWD) vehicles that have halfshafts, the shafts connect the differential to the drive wheels.

Q. How do you know if a CV joint needs to be replaced?
A. Most CV joint failures occur as a result of a boot failing first. The boot keeps out contaminants while keeping the grease inside the joint. If the boot fails, the grease leaks out and contaminants get inside the joint.

Symptoms that may indicate the need to replace a worn CV joint or the complete halfshaft assembly include the following:

•A popping or clicking noise when turning. This almost always indicates a worn or damaged outer CV joint.

A quick way to verify this condition is to put the car in reverse, crank the steering wheel to one side and drive the vehicle backwards in a circle (check the rearview mirror first!). If the noise gets louder, it confirms the diagnosis and the need for a new joint or replacement shaft assembly.

•A “clunk” when accelerating, decelerating or when putting the transaxle into drive. This kind of noise can come from excessive play in the inner joint on FWD applications, either inner or outer joints in a RWD independent suspension, or from the driveshaft CV joints or U-joint in a RWD or AWD powertrain. Be warned, though, that the same kind of noise can also be produced by excessive backlash in the differential gears. A quick way to verify the diagnosis here is to back the vehicle up, alternately accelerating and decelerating while in reverse. If the clunk or shudder is more pronounced, it confirms a bad inner joint.

•A humming or growling noise. Sometimes due to inadequate lubrication in either the inner or outer CV joint, this symptom is more often due to worn or damaged wheel bearings, a bad intermediate shaft bearing on equal length halfshaft transaxles, or due to worn shaft bearings within the transmission.

•A shudder or vibration when accelerating. Excessive play in either the inboard or outboard joints can sometimes cause this, but the most likely cause is a worn inboard plunge joint. These kinds of vibrations also can be caused by a bad intermediate shaft bearing on transaxles with equal length halfshafts. On FWD vehicles with transverse-mounted engines, this kind of vibration also can be caused by loose or deteriorated engine/transaxle mounts. Check the rubber bushings in the upper “torque strap” or “dog bone” on the engine.

•A vibration that increases with speed. This symptom is rarely caused by a failing CV joint or by FWD halfshaft imbalance. An out-of-balance tire or wheel, an out-of-round tire or wheel, or a bent rim are the more likely causes.

Other items that should also be inspected when investigating drivetrain or suspension noise:

•On FWD transaxles with equal length halfshafts, the intermediate shaft U-joint, bearing and support bracket should be inspected for looseness by rocking the wheel back and forth and watching for any movement. A bad bearing would call for bearing or shaft replacement.

•Transaxle oil leaks around the inner CV joints. This would indicate a faulty transaxle shaft seal. To replace the seal, the halfshaft must be removed.

 

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