First of all let me say this is new territory for me.

I recently replace the 305 tbi engine in my 91rs with a 355 vortec set up for about 375hp and near 400ft lb torque. The 700r4 in the car had a recent rebuild by a local shop just before I got the car (500 miles ago). I do not know exactly what was done to the trans.

The problem is the trans shifts fine at part throttle but the 1-2 shift at WOT is very slow. also the 2-1 downshift is very slow at WOT. I have not yet done a 2-3 or 3-4 shift at WOT.

I would like to firm up the shift at WOT because I know the way it is currently shifting it will destroy itself. However, I do not wish to have bang shifts at part throttle. I have done much searching to determine what to do with this trans and I am very confused. My fear is if I install a full shift kit that the bang shifts will destroy drivetrain parts with the engine I have installed. I would prefer to simply find a way to firm up the WOT shift without putting excessive strain on the drivetrain.

Would a corvette servo or billet servo help? How about a larger diameter TV boost valve?

Any recommendations on specific parts to order to firm up the WOT shifts would be welcome.