When i'm in 3rd or OD and i let off the gas quickly, i get a pretty hard clunk from the motor/tranny. I've checked and replaced motor/tranny mounts, and it's still happening. It only happens in 3rd and OD so i'm pretty sure its the torque converter. Anybody have experience with this?

 

I've seen the 4 bolts on the TC back out before but usually they start rubbing and it makes a grinding sound.

Thunk could be from driveshafts having worn U-joints. quick way to inspect these are to block the wheels good. apply parking brake and normal brakes. watch for shaft movement while someone places car from rev/drive/rev/drive. sometimes you can see one side of the joint move while the other half doesn't.

if not atleast you should be able to hear your thunk and trace it down