A manual valve body "reprograms" an automatic transmission so that you have to put it in whichever gear you want. If you put it in 1, it will be in first gear and stay there until you move the shifter. If you put it in 2, same thing, etc. There will be no automatic shifting. You have to start out in first gear, and "manually" shift the transmission. When you come to a stop, you have to shift back down to low gear.