How to Test a Halfshaft U-Joint

by Doug Braun

Here is a good test for these joints:

1: Put the top up, and you can hear it better
2: Coast about 20-25 mph in neutral and do some gentle S-turns
3: If the noise gets louder when you turn left, it's the left joint, etc.
4: If you turn the opposite direction, the noise should almost disappear
   if you turn just the right amount.
5: If the noise doesn't change when you turn, maybe they're both bad...
6: If you apply power, the noise should go away (because you are loading up the 

The cause of this noise is the side load imposed on these U-joints, which causes the joint 
to go "click-click" as it slides back and forth sideways.  The axle shaft normally exerts 
a downward force on the differential. As you turn, the side load on the wheel can increase this 
force or neutralize it, depending on which way you turn.  To visualize all of is, think of the 
axle shaft as a lever, with the suspension joint at the hub being the fulcrum, and the wheel 
exerting an upward force a few inches further down the shaft.

It takes very little endplay to allow this to happen- If you try poking and prying at the 
joint, it may seem fine.  A while back somebody described how the fitting of thicker circlips 
or shims could fix this problem.

I do not think this is a big safety issue; if the joint gets truly worn out or damaged (e.g. 
cracked or siezed needles) it would make really evil sounds. One of mine is clicking, but 
I am too lazy to get all tired and filthy crawling under the car right now to fix it...

Doug Braun
'72 Spit

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