Is youre jeep lifted? I've read that a lift greater that 3" may cause some driveline vibration. I was fine until I hit 4" then I ended up having to do the SYE / CV shaft install.

 

AFAIK everything is as stock as can be. Stock tire size too. That does however give me another place to look if all else checks out.

If for some strange reason the angle is wrong I can check it. According to the table below, It should be 4 - 5°.As I'm writing this AND checking the manual. I see that the adjustment for the rear axle pinion input (Differential angle) is done with shims where the axle connects to the leaf springs. So, although it's not been lifted, over time these could have moved, or someone replaced something and didn't set the proper angle. More to add to the list of checks. Finding and inclinometer for a reasonable price might be a bit tricky.