I've been trying to figure out why my rear pinion u-joint keeps blowing. With the driveshaft off and the tires on the ground the pinion can rotate with about 25 degrees of slack. Should there be that much play in the rotation? Running a dana 35 with an aussie locker.

25??? If the problem is that severe then you could be stressing the u joint by putting it in gear. If its an auto tranny it slams it when you go from D to R. Manual will still do it, just maybe not as hard depending on how you drive. Is there any up,down, side slop in the pinion?
Pinion bearing could be wasted.

Unless it has something to do with the aussie. I have never run one so i dont know much about them.

If you call Aussie or Detroit, they will tell you that is at the edge of normal. Not real common, but not neccesarily bad.

Oh, and 25 degrees is nothing. Do you mean 1/4 turn?

I guess put in the 1/4 turn perspective, It doesnt seem as bad as 25 ° did to me at first. :shaking: Long day.
Are you running leaf springs. Axle wrap?

1/4 turn would be 90 degrees...

Manual tranny in a tj, just did an advanced adapters sye and tomwoods cv, still blew u-joint. 2.5 lift with t-case drop. Posted earlier and everyone agreed the locker wasn't causing it. Pinion angle is good at rest but u-joint only blows when driving off road. Could the joint be binding up when the axle drops while recieving tthrottle?

Sounds like it could be pinion angle and when you get to more extreme angles something is binding. Why are you using a T-case drop with a SYE and CV shaft? How long is your drive shaft?

If you happen to know anyone with a forklift then I would try and lift each wheel to the max it will go without other wheels coming off the ground and check for binding. Ramps work just as well.

A little play in the yoke rotation is normal. I heard it everyday I put the CJ7 in gear. The detriot with the auto just bangs back and forth. But it is completely within design parameters.

First time I installed it then drove it, I was sure I set the backlash wrong, took it apart and checked it. Called a few friends with the problem and they all have the same thing.

And once again some pictures would help.:shaking:

I've seen a handful of D35 yokes "stretch" to the point that there's space between the tooth/spine that holds the caps on the ujoint. Check that and order up a replacement, it's an easy fix and worth it to not blow joints all over the place. Make sure you've got the right socket and torque wrench.

on my fourth yoke in a year, probably ten u-joints, and now on my third driveshaft. when the u-joint lets go it takes everything out with it. cv driveshaft helps the t-case end but does nothing for the pinion angle or strength of the pinion joint.