8 3/4 rear clunk when brakes are applied

I had a similar..clunk..in my 8 3/4 s.g rear last year.Turns out it was the cone style sure-grip was kaput.I purchased a used centersection and had my 4.10 gears installed in it,then installed the center myself.Works fine now.That,s what my clunk was,yours could be different.My 2 cents.I,d start searching for a new center,they run anywhere from $400-$600.but there is still some cheaper in these tough times.Good Luck!

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