It's been a while since my last post here but I have been a part time lurker and now I have come upon a problem I'm am having a little trouble with the best solution. I have done research and found two answers and would like to hear from other people's experience.

Jeep specs: 8.25 axle, 242 transfer case, aw4 transmission, 3.5" RE suspension.

I had zero vibrations when I installed the lift with the original Dana 35 axle. I blew out the LSD and had lots of metal shavings in the diffential so I decided to just upgrade to an 8.25. When I installed the 8.25 I kept the drive shaft from the Dana 35 as it was a half inch longer and I figured this would keep more of the slip yoke more engaged especially with the differential further away from the lift. This all worked well for over a year still with zero vibrations.

I lost the rear universal joint on the highway and the driveshaft and differential yoke wear both damaged. I have replaced the yoke and installed the spare driveshaft that came with the 8.25. I get vibrations at around 25-30 mph now.

I think the first step to try to remedy the problem is to correct the pinion angle, I will consider and SYE if that does not work. I have measured the following:

Drive Shaft: 18*
TCase Yoke: 5*
Pinion Yoke: 9*

Do I adjust the pinion down 4* to match the Yokes? This seems logical in the sense that the u joints will move in equal and opposite positions and create balance. This would have the joints operating at 13*.

Do I adjust the pinion up 9* to match the drive shaft? This seem logical in the sense that the u joint at the pinion will have minimal movement and reduce vibrations at this joint as it operates at 0*.

What solutions have you guys used. I have researched and found information on both scenarios.

Thanks for any input.

 

Watch this -

 

I fought this hard and finally solved it by dropping my Jeep back down to "Upcountry" ride height. Or what is supposed to be...using Moog progressive coils and Dorman leafs. It rides pretty smooth now.

However, I had it at about 4", with 8.25 replacing the Dana. I tried 2,3 & 4 degree wedges, TC drop, etc. At one point I thought that having the two shafts parallel would be the thing to do and I got them almost exact...but nooo. There was too much angle on the U-joints and they were NOT happy.

So the next thing I tried was to re-install the 1" TC drop (yeah...I know) and then wedge the pinion upwards. Basically pointing the two shafts more towards each other. This was better and more within the "window" but still not perfect.

So...my conclusion after lifting two XJ's and LOTS of mucking around with this stupid driveline vibration problem is that the best possible solution (and the one the factory should have done to begin with) is to install a SYE setup. If you search this forum (which you should), everybody that asks this question gets the same response: "Get an SYE." Its not BS.