I have a 2001 XJ. Prior to lifing 3 inches, I noticed serious vibration at speed. I went ahead and lifted the XJ and pulled the front drive shaft and the vibration was gone. Easy fix right?
Replaced the shaft and still at about 65-70 vibration is back with the new shaft. WTF?!?
Question I have is:
Did The lift cause the vibration issue since I didn't do a TC drop? OR
Is the new shaft a POS and needs balancing?

I bought a no name brand shaft for $200. The drive shaft place wanted $400 to fix my original. Hell, I've seen some gee-whiz-bang drive shafts brand new for $400.
I don't off road all that often so went with the El cheapo. But guessing I got what I paid for. Thanks

 

TC drop only makes the angle & vibes on the front driveshaft worse........not better.

You have some other problem that only surfaces when the driveshaft is in.

Have you checked your front pinion bearings ? or front t-case output for play ? Have you checked the t-case linkage ? Are you SURE you are in 2wd, and not stuck in 4wd ?