Rear Driveshaft Length?

I only have about 1/4" of in travel on the stock driveshaft. It's causing trouble, damage to the rear pinion seal. I'm sure the TC isn't happy either.

How much "IN travel" should I have? RR YJ spring conversion.

Thanks

 

There is a shop nearby. I just need to know how much I need to have it shortened? only has about 1/4'' of travel now.

 

I would guess a drive shaft shop could tell you what the standard is for free play. For mine I did some triangle math to prove it wouldn't bottom out even if the axle went all the way to the bump stops.

 

Anyone have an "about ___inches" ?

Algebra isn't going to happen no less geometry.

 

I think my stock setup is in the neighborhood of an inch to an inch and a half. I can check later in the week if nobody else chimes in.
Edit- I found some old notes. I have a bit more than an inch.

 

Jack it up from the frame and see how it looks, then put it down and fill the back with weight until you bottom out. Divide

 

They said there would be no Math!!

 

Drive shaft shops only need, (wheels on the ground.) center of u joint to center of u joint. If you give them give them this info and your drive shaft. They can tell you if it is the right length.

If you did a YJ lift. Your drive line length should get longer. As for your seal problem. Drive line length won't cause pinion seal damage.

 

Ok good. I’m learning as we go here. Really surprised that when I just pulled the shaft the total travel is only about 1 1/8”.

 

Does this look like an original drive shaft?

Is 1 1/8” travel normal?

 

Hard to tell. If it was professionally done, you couldn't tell.

 

I have a spare original at home. I can take some measurements and photos Wednesday if you need.

 

a good drive shaft shop . will calculate what slip needs to be built in . with vehicle flat on ground
give the center of front u joint to center of rear u joint

 

I pulled the shaft from the donor cj7 in the driveway. It has 2 3/4” travel. It would need to be cut lots more but I don’t think that will be a problem.

 

You will be surprised just how little travel you actually need. As the rear suspension compresses, the rearend moves backwards, negating some of the shortening caused by the upward travel. 1/4" however is probably a cutting it a little close. If You are going to change your transmission in the near future, I would leave it alone for now as you will have to shorten the drive shaft when a 4 speed is installed.

 

Good point.