At the heart of every automatic transmission, is the valve body. The best upgrade available is modifying your valve body with a Transgo Shift kit, Superior shift correction kit, Sonnax Zip or Sure Cure kit, or the Fairbanks Transaction Selective and Posi Shift 2 Stage kit. The benefits of a good valve body kit include longer life, better shifting, and lower transmission operating temperatures. For HD and high-performance application an HP kit will provide quicker or firmer shifting, and allowing the transmission to handle much more HP and abuse over the stock configuration. We have shift kits ranging from stage, 1, 2, and 3 full manual. In many cases, installing one of these kits can extend the life of the transmission by many miles, by simply fixing or solving the problems your transmission had from the factory. OPT recommends a shift kit be installed with every rebuild, but many people do install these kits early in the life of their vehicles just to ensure they get as many miles as possible from their automatic transmission. We have found cases where a shift kit installed in a newer transmission can easily double the life and avoid premature transmission failure.