A shift kit will bring the "line pressure" up. That is the pressure that the transmission operate's at. it will increase pressure to the applied clutch pack, it will hold tighter, than it did in the stock form.
Not only the line pressure, but quicker, firmer shift's are a must in any auto trans. The factory has less line pressure, and smooth shift point's, to make the "normal" customer happy, so it shift's smooth and easy.
Any off road auto, deserve's a shift kit period. And add a large capacity oil cooler to the mix also. It will make the newly overhauled, shift kitted, tran's, live a long, happy life. /forums/images/graemlins/thumb.gif