First off i have a 2008 LGT with the stupid 2nd to 3rd shifting thud. Well i brought it back to the dealership the first time and all they did was the quick "reflash" of the TCM/TCU. well long story short that didnt fix the problem. So i brought it back to them months later for the same issue (finally couldnt deal with it anymore) and they did a complete reflash of the TCM and that fixed it. as of right now you cant feel any of the shifts really. Its unbelieveable how much better this car rides. Ill go out to my car once i finally wake up and get the paper work that they gave me incase anyone needs anymore info.
I figured id let people know that had this problem that there is hope lol