Ok... This thing scared the crap out of me today.
Note: track bar, tie rods and shocks are all brand new..
96 xj 4x4 108k miles stock suspension 31/10.5/15 tires like new..
This thing drives nice at or below 60 on pretty much any road.. however it tried to kill me on the freeway. I'm going about 70 coming up on a rougher part of the freeway.. frost heaves etc. The first one just makes the normal thump thump sound... 2nd one the back end feels like it got kicked by chuck norris from the passenger side with all kinds of noise.
It feels... odd.. its worse on right hand turns and almost never happens on left hand turns.
Tires are like new and balanced as well. It also does it if I am accelarating hard and hit a bump, then its pretty insanely.

Going under and looking I see nothing that jumps out and goes hey I'm broken!
My Only guess is bushings? Or maybe saggy leafs?

 

One other symptom seems to that the passenger side
rear suspension feels "stronger".

 

Hm... Are your leafs saggy or broken, any of the rear shocks blown i know you said they are new but if you hit a pothole hard enough it could blow All the shackles look ok? Take some pictures under there some times it hard to see with the naked eye... Also I would check to make sure we're your rear shocks mount did not break... Make sure the rear shock is still connected in the mounting plate... I have seen that happen... You need to pull out the rear plastic to check this tho but is worth a look ...

 

Missing bump stops?

 

Jack it up, sounds like wheel bearing.

 

I think i would be checking the lug nuts. I have an 79 chevy 4x4 and had the same kind of sounds. Come to find out 2 of the lugs snapped off. Causing the rims and tire to bounce around on the studs. Good luck keep us posted

 

The leafs are a bit saggy! Shocks are mounted nice and solid. The shackles look original' very short little things.

Yes it has bump stops' bit its not bottoming out. I. Checked for structural rust as well this morning and it passed the screwdriver test.

Seems like its down to the leafs/shackles?

 

I guess I should have said its not a grinding sound, but that the back end dodges off to the driver side. Almost feels like a broken panhard bar on a coil spring setup, but it only wobbles one direction Lol.

 

Wheel bearings dont always make grinding noise. Still Jack it up and try and jerk tire around, its a possibility.