I purchased my 91 XJ back in march and after getting it from the city to the woods (dirt roads) where I live I noticed a pop in the driver's floor when turning left.
I had been under this thing today makes three times checking EVERYTHING and finding nothing worn/loose.
I was prepared to start from one side to the other and replace EVERYTHING in this front-end to get rid of the pop that was driving me nutz.
I then remembered this forum I joined back in 05 and was going to start a thread but did a search first. I found this thread;
http://www.automotiveforums.com/vbul...t=Steering+pop
The two lower track bar bracket screws I was able to tighten about a half turn each, I was skeptical this was the problem till I took it for a spin. I would have never believed these two screws would have caused this pop.
Thanks AF and ALL who post their experience 
BTW, I'd been
had I rebuilt this whole front-end and still had that freakin pop....