i did this but cant remember the length. measure the difference between the two transmissions and thats what you have to shorten the shaft. it was only 2 inches or so. wasnt much82supremeproject said:i swapped in a tbi 350/700r4 and computer/ harness out of a 1989 c1500. i know i need to have the drive shaft shortened but i am not sure how much i need taken out. can anyone tell me how much i need to have the original drive shaft shortened swapping from a 3.8/auto 3 speed to 350/700r?