High speed Vibration

HELP!! OK I'm pulling my hair out here, and there wasn't much there to begin with.. Here's the back ground... It's an 87 XJ Wagoneer with 4.0/AW4/242... Never got to drive it at hiway speed before lift as it was a builder.. So I did a Rancho 3" lift with 31" tires.. Did 1/8" shims on LCA's to correct caster.. Now I have a vibration starting at about 55mph. It's coming from the front driveshaft.. I've pulled the front shaft and it goes away. So I had it checked and balanced at a good shop and it showed good up to 85mph. Checked axle and tcase bearings and they look good.. Haven't checked the pinion angle but with only 3" of lift it really shouldn't be a problem should it? SO what am I missing? I want to add another 1-1.5" of lift but need to find the vibration first.

Thanks
Keith

You do need to check the pinion angle, also did you replace the u-joints on the driveshaft. Most importantly is the ones in the cv joint. Or at least give them a good greesing. Just a thought.

Thanks juicexj24 I checked the single u joint and had a drive line shop check the other joints. They also ran it on a balancer and it showed good to 85mph... I'm going out to check the angle now..

Thanks
Keith

I had a similar situation and turned out to be gears set-up incorrectly. Had the ring and pinion installed and within 100 miles the bearings were shot. Had to have it all redone (by a different shop the next time). That's an expensive change though. I'd keep that as a last resort if you can't seem to fix it any other way. Could also be bad hub bearings assembly thingies. Same as with the R&P, the vibration is just being transmitted through the driveshaft.

Thanks Watson but the vibration is not there if the shaft is removed.. I just checked the drive shaft angle. The shaft joint is at ~5.5* and the axle joint is ~3.5*.. So maybe alittle longer LCA? Also noticed alittle movement in the tcase output, more heard than felt.. Would this cause the vibration? How hard is a 242 to rebuild??

Thanks
Keith