My automatic transmission is making a strange noise. There is an intermitant thumping noise comming from the transmission area while in drive at most speeds. The noise is more prevalent during de-acceleration, but still intermitant. Also, when stopped, with the parking brake on, the car is in reverse gear, and the engine reved just enough that it doesen't overcome the parking brake, there is a continious dull thumping/grinding sound. It only does this in reverse. This all seemed to start when I went over a train track and normal speed. Right after the car came down on the springs I heard a loud smack type noise. QUESTIONS:

1) What would be turning in reverse when the car is not moving. Torque conveter?

2) Does the drive train rotate at all when the car is not moving while in reverse?

Second request. Thanks for any help

Scubyvegan