Shims?

Brother has a 3.5" RE short arm lift. Eating U-joints like crazy.

I'm pretty sure it's closer to 4" than 3.5". Have not confirmed though.

Anyways, he bought 4* shims. I'm looking at them and they look like a lot.

Does that sound right to you guys or would you go with 3*?

Guessing no SYE kit?

What does the pinion look like compared to the t case yoke, hard to say without actually measuring the angles...

Forgot to mention. He has an IRO HNT. NP242.

Would you happen to have the diagram for the angles I need for a front driveshaft in the rear?

Thanks.

if you are using a SYE and a CV shaft, just rotate the axle up enough so the pinion is almost in line with the shaft. Leave it maybe a degree down to allow for spring wrap under acceleration. You will need to rotate it a good bit as setting up a CV shaft is completely different than a U-joint shaft, where you want the pinion to be about a degree down from the tailshaft of the trans or transfer case.

Something like this can help with your setup

http://www.lowes.com/pd_198122-1099-AF006M_0__?productId=1057041

see here

http://www.4xshaft.com/

(scroll down to bottom of page)

oh, easy way to figure this out. Pull a string from the 2nd cardan of the CV joint to the approximate centerline of axle while parked on a level surface. You'll have to go off center, no big deal as you will see. Take your angle finder while a helper holds the string taut and measure the angle from the string to horizontal. Then measure the angle of the rear pinion yoke to horizontal. The difference between the two minus approximately one degree is the shims you should try first.

This is what i should be looking at correct?

Thank you n8n. That actually makes perfect sense now that i actually think about it.

With a sye you want the pinion 1 to 3 degrees below the ds angle to deal with axle wrap on acceleration. It's most noticeable when you are trying to climb a ledge with the rear tires. Watch that puppy wrap up bad.

Yes, that's the right diagram... if your brother just added a SYE and front driveshaft to a stock axle, it's probably pointed way down as the XJs came stock with a u-joint style driveshaft. And what jon said about pinion. I said a degree based on my experience with street driven cars, maybe more is warranted if XJs are particularly prone to spring wrap.

Finally understanding this concept.

Is axle wrap related to the fact that if i hold my foot on the brake pedal in D, and give it gas the back of the jeep lifts itself up into the air?

you can probably find videos on google, the rear pinion literally wraps up and get the angles all out of whack.

see this axle wrap up :

https://www.youtube.com/watch?v=54_6GaYJvWI

ummm... yeah.... that is pretty bad...

But the tendency is for the pinion to lift under power/acceleration in any leaf spring vehicle because the axle is trying to rotate opposite the direction of the tires and only the springs are constraining it.

I built a '55 Stude coupe with a R1/4-speed/3.73 LSD, previous owner had cut out the support for the two piece driveshaft, so I just went with a one piece... never did weld in the 63-64 Super Hawk traction bars that I scrounged... the driveshaft would hit the floor if you nailed it hard enough in first gear, probably not a Good Thing.

Now that you've presumably watched that video, I think you can see why people who use lift blocks are laughed at... imagine what happens with an additional inch or two of moment arm between the axle centerline and the leaf springs when you stand on the loud pedal.