I have a 2001 Cherokee Classic, 4.0 automatic, 4x4. I noticed a strange vibration and noise when 55+. Especially when coasting. I was thinking pinion or rear bearings. So I did one more test. I put the rear end on jack stands and ran it up to 60mph. When I let off the gas a loud clanking noise came from the transfer case. The u-joints are solid (recently replaced), the rear end is nice and quite. The shaft coming out of the Transfer case is in the same plane as the differential.

Transfer case has fluid, though it was low.

I was thinking the Chain also, but with the front tires on the ground and the rear spinning, the chain is should no be moving right?

 

https://www.youtube.com/watch?v=bW57...99969051289052
Here is an example.