Just got the xj highway capable thanks to a shopping list of new front end parts and tires.
At any point I let off the gas, I get a grinding binding type sound. It's not loud or harsh. But certainly is causing extra wear on something.
I get small vibes up to 35mph that go away and a very light vibe between 65-70.
I have 3.5" lift that's still settling. As I'm still at about 4.5" I have 3* shims in the rear as well. I'm thinking the slip yoke is extended out to far causing the extra slop and vibes. I'm thinking about doing a tc drop to aid in this. Sound right?
In the spring I'm thinkin bout adding 1" shackles and 1.5" spacers to level it out and aid in rear flex and ride quality. That is if I can get away with just a tc drop.

 

Put the tcase drop in, it's like 40 dollars or something. If that don't work, go ahead and buy yourself an SYE (200) and put it in yourself, then get a driveshaft off the front of a 4.0 auto Cherokee from the junk yard and use it in the rear.

 

Could be a pinion bearing... I have a pinion bearing on its way out and I am experiencing the same thing as you.

 

It started when the lift went on. Before that it was fine.

 

same thing here did a tc drop and still need to do sye, the lift has settled a bit and the clunk grind went away but the vibes are still there. 35-40mph and 55-60mph most noticable

 

Im thinking its your driveline. You probably need an SYE or a tcase drop as a temp fix.

 

x2