Clunk in rear end-95rmw

For the last couple of months I've noticed a distinct clunk in my rear end when shifting in reverse and sometimes when decelerating, especially to a full stop. My mechanic checked it out and said universals were ok, but when he put it up on a lift and would put into R he could hear a distinct passenger side clunk within the differential. Otherwise he said everything looked fine -nice and dry etc. he suggested going to a transmission shop.. I've continued to drive the car for another month or so around 4000 miles and it hasn't gotten any worse. If anything it seems to be a little better. Other than the clunk the car runs and drives beautifully. Currently at around 118k. Any ideas ?

Thanks for any advice

Have you ever changed the rear end fluid? And assuming it's a posi, did you put in the additive?

Tom

I don’t know about fluid change before I got the car. It had 88K on it when I got it. I haven’t changed it. I suspect the previous owner might have but can’t be sure. It was a 1 owner by an older gentleman that bought it when he retired in ‘95 and only put on the 88K in the next 23 years. I had the car fax and it showed regular maintenance at the dealer where he bought it and lived in Florida. How can I tell if it’s posi without doing a burnout?

Easiest way to tell: look under the hood, if there is one mechanical and one electrical cooling fan then it has a posi rear end. The vehicle label, I believe it is located on the rear door will have a code G08, indicating a posi rear end.

Tom

AXLE,REAR,2.56 RATIO 2.56R(GM8) Is what came back fro VIN DECODER

Check your SPID on the gate pillar. It will have other G designations. let us know what they are, if any. The clunk could be gear lash, or a worn axle with a leaky seal. If the seal is leaking, you may have grease on the brakes, and it could cause the shoes to stick to the drum. Pull the RR drum, and check for grease. The axle should not wiggle when pushed front to back/up and down.

To check for fluid depth in the rear, remove the plug, and stick your finger in the hole. Fluid should be at the bottom of the hole.

The 2.56 gear did not come with limited slip from the factory.

The alert to this post go me here, and I thought of another possibility...It could be a bushing is worn out.