1990 Jeep Cherokee Death wobble

Your wobble is caused by worn u-joints just inside the front wheels. You'll have to remove the entire from wheel from the hub nut in and I believe the axles to get at them. My sister-in-law's jeep had the same problem and it also was the worst when she went over a railroad tracks. It would start vibrating uncontrollably. Her u-joints were about ready to fall apart. Some of the needle bearings were almost dry. I changed hers in my garage and it took me about 6 hours to do both front wheels. If you want to check them before repairing put the front end on jacks and grab both sides and top and bottoms of each wheel and check for play. Most likely you will find a lot of play in both wheels (they should be tight) and most likely coming from the worn u-joints. Good luck!