The B&M® Transpak is the next step up from the B&M Shift Improver kit. It has all the features in the Shift Improver kit, plus it provides additional driver manual control (GM TH-400, 350, Ford C-6 and Chrysler Torqueflite only). The B&M Transpak™ for 1967-1991 Ford, Lincoln, Mercury C6 automatic transmissions recalibrate's your C4 transmission for optimum performance to best suit your needs. Most stock automatic transmissions won't downshift into low gear above 15 mph, and automatically upshift at a predetermined speed no matter what gear you're in. With the Transpak, you can downshift at any speed, and you can hold the transmission in first gear to any speed that you want! This is an asset when you've got a modified engine, and you want additional RPMs, or you're towing a trailer or driving heavy loads downhill. Stage 1. Heavy Duty is for street rods, normal passenger vehicles or other heavy duty use. Firmer shift feel but not harsh. Improves transmission performance and life dramatically without loss of comfort and offers normal automatic operation when in Drive. Stage 2 is for Dual purpose performance vehicles, Hi-Performance Street/Strip, Off-Road/desert and 4-wheel drive use. Stage 3 - Competition use Only. Not for Street use.