These transmission kits increase line pressure in the transmission, which reduces torque converter and transmission clutch slippage and improves shifting. Easy to install using basic hand tools. Bully Dog's shift enhancers improve shift and line pressure while reducing slipping and lowering heat. The end result is firmer, quicker shifts which vastly improves the driving experience and longevity of the transmission by lowering transmission temperatures. The shift enhancer will fit in all E40D and 4R100 transmissions.