I have a 4L60E in my 1997 LT1 Camaro. What would cause the transmission (or even driveline) to bang into gear? It only happens when the engine (and transmission for that matter) is at operating temp. It also only happens when I shift from reverse to drive or vice versa. If I go from park to drive, it shifts fine.

Any ideas?

 

Many "bangs" are due to a worn out (or too stiff Poly) trans mount.

Beyond that I would scan for codes. Some engine sensor problems can cause the PCM to command maximum line pressure in the trans which can make all gear changes very harsh. People usually notice it as a very harsh 1-2 shift.