ST205 Rear clunk on take off and low gear downshifts?, Had it checked out, Can't figure it out. Options

[salv]

While driving one day after downshifting from 2nd to 3rd I heard a loud clunk in the back end of my car. Whenever I drive off from a stop I would hear the same clunk. If I'm in first and I let off the gas I can hear the loud clunk.

I checked online and many Celica owners have said its the rear diff mounts.

I took it to a shop today to have a look at it and they couldn't figure out where it was making the clunking noise from. We both thought it was from the rear diff mounts but they seem to be in good shape with no cracks. They suspected it was my drive shaft because it had play when turned left and right but we agreed that the noise couldn't come from that; (Plus I would have more then just that problem if that were the case).

The noise has been driving me nuts! Anyone have similar problems and possible ideas of where its coming from?

Symptoms are:

-Slight clunk noise when driving off from a stop
-Slight clunk when put in reverse
-BIG clunk when downshifting under high RPM load ( Going from 3rd to 2nd gear)

Cheers,

Sal