If all that don't fix it check the Tone Ring inside the differential... You will have to pull the Diff Cover and inspect each tooth...Any nicks, scars, missing teeth and deep scratches will cause it to bounce...

Easy to do if someone took the differential axles out and let the internal carrier drop on the housing right onto those teeth.

 

Doh. Wish i had checked the tone ring when i changed the diff fluid earlier this year. Brings up another thing thats been running through my head. After a diff fluid change, should the fluid look light brown and kind of runny? Or is this an indication of a bad seal somewhere on the rear axle?

Thanks for all the replies. I have my list of things to try when i got time. I traded off my car for another car needing some work. Been messing with that recently.