Sorry to resurrect this thread, but I was looking for some info on a very similar problem, and ran across it while searching:
My vehicle: '92 XJ, 4.0 / AW4 / 231 with 212,000+ miles Tires are Toyo Open Country AT P225/75R15, and I have been running them at about 30psi. Had them rotated and balanced about 4 months ago.
Had OME 2" kit (including shocks) + TCase Drop + Front Swaybar Discos installed a couple of months ago by a reputable local shop, and retorqued/aligned about 1000 highway miles later. I have yet to "disco" the discos as I have not been off-road since having this work done.
I have no complaints with the handling most of the time, but I do hear a bit of a clunk when I come to a moderate to hard stop. Additionally, I occasionally (not all the time) feel what I think is the front U-Joints binding, but only when I am just starting to come back from having the steeing at full lock (e.g. turning around in the driveway).
What I am finding is that on one particular bump on my daily commute my front end goes seemingly into a rather disconcerting wobble (entire front end shakes in a side-to-side motion) for about 5-7 seconds and then quiets down. I have only see this happen with this one bump, and it does seem to have gotten a little worse over the last couple of months (the XJ isn't the DD these days, but I take it to work once in a while to get it out and run it). Other road bumps do not seem to cause this, so it appears that there is something special about this bump (or type of bump) that sets the wobble off. Unlike 98XJSport, I have noticed no unusual tire wear.
I found Hoytinak's comment about the u-joint interesting - my front axle joints are probably the only ones on my rig that have never been replaced. I had the left front knuckle assembly replaced somewhere around 130,000-140,000 miles (had been installed crooked and stripped by some unknown entity), but I do not know if the ujoint was replaced as part of that job. The right front joint may be original to the vehicle.
Hoytinak, did you notice any other symptoms from your broken joint, or was this occasional wobble the only one?
Thanks,
Rob