Finding Driveshaft Length

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Apr 1, 2007
Peoples Socialist Republic of Chicago
Read through a bunch of posts and would love to find out how to determine the proper driveshaft length on my SOA'd FJ40. I have a static measurement for both front and rear but I don't know how long it should be under flex. How would I do this?
three ways:
1. measure flange to flange and supply this info to your driveshaft shop
2. take the truck there if you can and have them measure it. This puts the monkey on their back.
3. mount your existing DS, measure and mark on the tubing how much to add/shorten from a marked line of reference.

I have done #1 and got work that was too long or too short. It would work but not have the spline in the center of the slip & bottom-out on on suspension compression. I have asked for them to do #2 and was told if you can get it to us, we'll measure it for you. I have not done this as it's a PIA.

I have had the most success getting exactly what I want with the least amount of hassle by using method #3.
If you have access to a forklift (Gumbys) try to cycle the suspension to its two extremes. (compressed and extended) Take both of these dimensions to the shop with you along with the static length. If they know what they are doing- they'll know what length of slip to give you.

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