Ok all, here's the deal. My XJ is pissing me right the hell off. When I bought it, it was stock, so it drove just fine. After about a year, maybe a year and a half I lifted it to the point where it's at now- roughly 4" and put on a set of 31" BFG A/T's. There were no problems, no vibes at all to speak of. I drove it like this for about a year, until I came across a set of BFG M/T's. Again, no problems, no vibes. Until this winter, that is.
During all the storms this winter, I had the girlie driving the XJ and I drove the TJ. (This was problem #1 )
Then I noticed there was a vibe in the vehicle. With all the roads getting trashed, I figured it was the tires out of balance, so I had them rebalanced, but it was still there. I noticed that one of the tires was wearing really bad, so I figured that may have been part of it, so I also had it aligned. I replace all the u-joints in the driveshafts. I also pulled the front DS to see if that was the culprit- still there. I had also heard a growling from the front end, and traced that to the wheel bearings/hub assemblies, so I replaced both of those (those damn things are expensive too...). Vibe is still there. Since then, I have made sure everything was tight again, and also threw on my 33's, but I still have the vibe. With the 33's, the vibe is significantly less, but still pretty bad.
I have replaced everything I can think of, and I still have a vibe. The vibe is constant with vehicle speed- does not matter with engine RPM. I've noticed it as low as about 30mph because I'm in it all the time, but other people can notice it at about 45mph, and it gets worst at above 55mph. It's a constant vibe, not a shake or DW. So here's what I am thinking. The only thing I have left that I can think of is to have the driveshafts balanced. This is the only thing I can think of that would still be causing this, and I would have done it sooner, but couldn't figure out how they would have been out of balance- the XJ's gone through no wheeling at all. I know Arlo and I think one other person has had their DS's out of balance...does what I describe sound similar to what you had experienced? I'm at my whits end trying to figure this out, and I've gone through just about everything I can think of. I was thinking it might have been pinion angle with the lift, but I would have had vibes from the get go, and I didn't. Any ideas??