Drive line for a short box

[chris j]

I need a new drive line for my 50 GMC short box, can anyone tell me what will fit so I know where to start looking.

[OrrieG]

http://67-72chevytrucks.com/vboard/s...iveline+length

[mr48chev]

There are a few variables that come into play first.

1. Where you located the engine in the engine compartment. it may be a bit further forward or further back than what someone else has. That would affect the length.

2. What trans you are running affects the length.

3. What rear axle you are running affects the length.

What most guys do is slip a yoke in the trans and pull it out so they have between 1/2 and 3/4 of an inch of the yoke showing out of the seal if it is a flat seal. then with the rear wheels on the floor, or ground or the rear axle supported by jack stands with the weight of the truck on them they measure from what would be the center of the U joint in the loop in the yoke to a matching spot on the yoke on the rear axle. That should give you center of U joint to center of U joint measurement to go hunting with.

You also need to know what the measurements on the cross of the Ujoint are so you get the correct driveshaft in that respect.

Since Phil and Martha closed Autoscraps I don't know the wrecking yards down that way very well anymore. He could tell you right off what driveshaft to look for.

[Speedbumpauto]

After you do the measurement described by Mr. 48, you can go to the pick and pull armed with a measuring tape and find a healthy donor that is too long since finding the correct length is more than Murphy will allow in most cases. It helps if one or both of the U joints match but there are lots of "conversion" U joints that match shafts to yokes. Take your treasure to a driveline shop and have it cut and balanced to your measurement. I got a donor shaft for $30 and a shop here did the sizing/balancing for $95 so I got a custom driveshaft for $125 + it came from a 3/4 ton truck so the tube will hold up to the moderate BBC power I have.