Hey guys. I've owned this 98 xj for a few months now, and it had some chirping and rumble noises. I removed the front DS to eliminate that possibility, and rebuilt the double carden rear DS and the put in new ujoints.. the chirp is basically gone (occasionally it's still there) but the rumble/vibration noise? is still there...
The rumbling sounds start when im up near 45mph and i feel it most when in 4th gear and am coasting down from 45mph. ill hear it all the way down to 15mph sometimes as it down shifts.
after searching around online and in facebook groups..My thought is maybe the previous owner took off the yoke of the driveline and when putting it back on maybe didn't line up the weights on the DS? could it just be slightly off? is that even a thing? or maybe im totally wrong and my Tcase needs new bearings or something. just want to rule out the driveshaft before I get a different Tcase. or have new bearings put in.

Pull the rear driveshaft, drive it in 4x4 and see if the vibration goes away.

I didn’t know I can do that! Be a front wheel drive ? How fast can I go like that?

As fast as you need to.

Update time. So I crawled under there to remove the driveline. And thought I’d check something first. The linkage under there. The gromits all look pretty decent. But one of those linkages (the one that connects to that bracket against the underbody) is very wiggly and moves when you push it. Not knowing how to remove that, I grabbed a rubber piece and cut a piece of towel, wrapped it, and shoved it underneath it so it has pressure upward. When you shake it it has minimal movement now. I test drove it and I don’t hear 80% of the rumbling now ...