This one is a head-scratcher. I've been hearing a pop or thunk noise once in a while. It happens maybe twice in a 20 mile drive. Usually when I'm starting from stop, but sometimes when the car shifts into 2nd gear. I've got a '90 GTA with WS6 suspension and about 100k miles on it.

Definitely seems to be coming from the back of the car. I checked the rear differential - drained the oil checked for wear or broken teeth - and everything looks good. I replaced the U-joints. Neither helped.

My buddy who has some mechanic experience said it sounds like maybe the suspension is settling or popping into place, but he was stumped. Anyone here have any ideas what might be wrong with my car?

 

I doubt that it's really a head scratcher when you take a good look...

When does it do it?

My first guesses if it's really a popping sound is something like the springs/spring isolators. Other obvious noise makers in the rear suspension are loose fastners, worn out bushings and broken TA/tranny mounts.

 

Thanks for some excellent advice. Turns out it was the transmission mount. It was completely ripped in half. Took about 45 minutes to replace because I am slow.