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). B&M® Transpak™ kit for 1965-1987 GM TH400/375 automatic transmissions. 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 Hi-Performance street use. Essentially the same as Heavy Duty mode except shifts are much quicker. Retains full automatic features and standard shift points with selector in Drive.