You need to track down the loose component, in most cases it is a worn out track bar. While I'm not really a fan of RC you really can't blame them for old parts being worn out.
If you have someone to help you the easiest way to find the broken or worn out parts is to have someone you trust hop in the drivers seat. Once you have positioned yourself where you can see all of the Steering components your helper should shake the steering wheel back and forth with the engine running. While this is occurring you should be looking at the joints for movement. Typically the track bar is the first item to fail, but once a part has failed and wobble or shimmy has started, it tended to stress all of the other associated parts. Wobble can be caused by: worn joints in a track bar, a track bar that is bending or flexing, worn out tie rod ends, worn out control arm bushings, a bad or out of balance tire, Caster angle, worn out ball joints, or bad universal joints. With an 18yr old Cherokee it could be any single one of these or a combination of them.
If you are looking for the best on-road ride with off-road capabilities then you will want to replace your current RC lift with a Long Arm lift of your choice, Over The Knuckle steering kit (or High use a High Steer replacement Knuckle), and an upgraded track bar with double shear replacement mount. If you haven't done so already you will need longer brake lines with a 4.5" lift and an Slip Yoke Eliminator may be need if you end up with driveline vibrations. If you want to stick with a Short Arm lift drop brackets can be used to improve the ride quality, but you will want to replace all (4) control arms.
Good luck and I hope you get the wobble sorted out quickly.
88 XJ-Lifted, Locked, and on Jackstands
69 CJ5-In peices