diagnosing worn diff in 505

nisspug2

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I've had a driveline clunk developing in my manual 1981 505 over the last few years and the last time this happened I had the tailshaft replaced and it fixed the clunk. This time when I took it to my usual mechanic he said he doesn't think its the tailshaft but a worn diff, which he diagnosed by turning the rear wheel and checking for play.

I checked this myself by jacking up one rear wheel and there is 1 to 1.25 inches rotational play measured at the top edge of the tyre. Does this amount of play indicate a worn diff?

I can feel the clunk mostly when I change gears when I have to feather the clutch to get a smooth shift, and also when cruising at say 2500rpm and suddenly increasing or decreasing the revs.
 
Would be impossible to detemine if it was the diff and not tail shaft and via versa by only rocking the wheel back and forth .

It may be a drive shaft , get a helper to rock the wheel back and forth and look and feel around the rubber boot . Does the inner goblet move with the wheel , if so then it either the tail shaft/ diff if it does not move its the drive shaft , repeat this test on both sides.
 
Yes makes sense. I'll probably have to wait until the weekend to have a look at the inner end of the drive shafts. Thanks for the suggestion. What about the 1-1.25 inch play - does that seem excessive?
 
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