I bought a 3rd Gen RX-7 in April with a blown motor. I fixed it up and when I first got it on the road, it would make this clunking noise when I brake...and it still does. Also, when I'm parked with the E-brake on and rock the car back and forth, it makes the clunking noise...it sounds like it's coming from the back. I checked everywhere and can't seem to pin point where this noise is coming from. I also realized today that I forgot to attach that aluminum bar (about a foot long with 4 big holes) that's located near the differential. Could this be the problem?

 

Had exact same problem when braking and it was the pillowball bushes.

Try this simple test - Jack up the rear of the car so that wheels are off the ground. Use one hand to push the wheel and the other to pull the wheel towards you and if there's any play then that confirms it. Because my wheel wobbled here I initially thought it was my wheel bearing but it wasn't.

Then its just a matter of taking off the Lower Control Arm and replacing the bushes.

Not sure about the diff though. One of my diff bushes are leaking and on its way out but still doesn't make any noise.

 

my car makes the same noise, I thought it might have something to do with the differential brace.

 

I've got the same problem! Besides the breaking bit! I'm pretty sure its the pillowballs... sounds like your are worse than mine! Do you have any clunks when you reverse?

 

Its your bushings, not too expensive but it is a pain to fix.

 

All six pillowball bushings from Ray at Malloy are $360. Ask me how I know.

 

$360. yikes!

 

How do you know?