Very common on the xj/mj for the frame end of the track bar to be loose.
It is a tapered stud, like a tierod end, and when replaced most of them never seem to get as tight as they should, and will eventually work the hole, and will give you a clunk or popping sound, like when turning into a driveway that isn't same level as road.
Mine both particularly did it when turning left off hwy, street not on same level as hwy.
Have someone lightly wobble the steering wheel while you watch, the stud is probably wiggling back and forth.
I have found the best way when replacing them is unbolt the bracket (4 bolts) and tighten the hell out of the stud.
It is hard to get it tight and lined up for the cotter key in the car.



I thought it was the control arms or shock on mine, too.