so my rx7 fc sat for around a year in california and i got it to az and i started driving it and it was fine at first then recently whenever i go from stopping to going the rear of my car makes a clunk noise and rocks back and forth it even does that when i immediately let off the gas it does the rocking back and forth and clunk noise. idk if its a bushing or the diff or some screw is loose.

 

The first thing I would check is the rubber mount for the rear differential. Its also a good idea to check the transmission mounts as well. The rubber deteriorates and allows rocking of the driveline under load applications.

 

i agree. it's probably the differential mount.

 

i did they seem all fine and not broken in anyway so rn im taking out the diff and taking it apart to check everything i might replace the bushings while im at it, there seems to be a lot of slack with the pinion gear idk if its a bearing or not im might be getting it rebuilt soon

 

While you're in there and have the driveshaft out, check the u-joints for play and for binding. A bad u-joint can cause a clunk under acceleration or deceleration. Another base to cover at any rate.

 

I had a similar thing with mine for a while.

The clunk only presented it self once in either direction under load. So with normal smooth driving no issues. But when I go a bit to harsh on it, or accelerate harder then normal, I would get the clunk. That clunk would then not come back, until it "clunked the other way" if you know what I mean.

couldn't find a thing, suspected the diff bushings but couldn't tell. Everything was hard mounted except the diff.

Late last year when I replaced oem diff for Kaaz LSD, I also replaced all 3 for competition bushings/mount and I cannot recall hearing the clunk since then.
Although I havent driven it much since then as it is parked during the winter.

So in my case i'm not to sure. Something internal that got fixed without knowing, or something with the bushings