This weekend I helped Jenny change the transmission mount on her XJ. While we had the cross member out we decided to remove the transfer case lowering blocks. This drop was put in to match the tapered lift blocks that came with her lift kit.
We removed the spacers and replaced the tapered blocks with flat blocks.
A test drive showed that the drive shaft vibes were back. I guess the drop is necessary for the 92. I have the same lift on my 88 with no transfer case drop and no drive line vibes.
We spent Sunday afternoon putting the transfer case spacers back in and replacing the flat blocks with the tapered blocks.
The drive line is now smooth again.