Mine also does the same, when running at speeds and downshifting it clunks not all the time though. it could do it 3 days outa the week, but when it does if i shut the car off and start agian , the problem goes away. Im thinking it could be the pressure valve inside the tranny. Wait for the peanut for answer'*

i had that same noise when i accelerated and then got off the gas. It was the tranny mount for me that fixed it.

mine feels like the engine is coming in to sit next to me

A faulty pressure control solenoid in the valve body for the transmission has been known to cause rough shifts. It'* possible that it could be the problem. Also, have someone sit in the car, with his foot on the brake, then put it in gear, and gradually increase the trottle in both drive and reverse. (Don't stand in front of the car during this.) Any unusual movement, or more movement than you'd expect to see?

Take a look at this tread, might help you out. I know tranny trouble is a pain!

http://www.bonnevilleclub.com/forum/...ighlight=p1811