I just installed a tranny (used but recently rebuilt & tested) in my wife's 03 LS8 & while it shifts a little better than the old one it still slams into reverse even after replacing the solenoid body. Think I might try this next, I cant afford a new one but I would like to find out what the new superseded part number is & try one.
http://www.gearsmagazine.com/view.ashx?article=e747f286-bc6d-4c53-977a-98d9306b794b
http://www.gearsmagazine.com/view.ashx?article=e747f286-bc6d-4c53-977a-98d9306b794b