Your car has a4T65E-HD transmission, the HD meaning Heavy Duty as this is what the supercharged cars came with and isnt much more than a larger differential and torque converter. The rpm drop still sounds pretty typical in 4th gear as the pcm gradually ups TCC duty% to make a full lockup but the two steps that it makes doesnt sound right. Typically what you will feel from a stop is this......
Take off from stop and shift into 2nd, then speed up more and shift into 3rd, then TCC will apply in 3rd gear and release momentarily as it shifts into 4th so you feel the bump into 4th and see the rpm drop, then TCC reapplies once in 4th gear again having a gradual rpm drop. The torque converter clutch is never 100% locked with zero slippage. The pcm wants to maintane a 2-50 rpm slippage at all times for a smooth feel, so when accelerating and TCC applies it will slip at bit before the rpms drop down a good amount and when you give it a bit more throttle the rpms will go up a little then pull back down as the pcm has to compensate for the greater engine load. If you are interested in tech manuals I have info on the ones that I offer here....
http://www.grandprixforums.net/f21/4...edge-8805.html
The GM Hydramatic book explains the fundamentals of the trans and goes no diagnostic info. It is pure information, sort of a the-way-things-work type of book if you will.
Originally Posted by Trannyman95
