I have a 98 xj. Everything seems smooth and drives fine at lower speeds, 0-55, when reaching highway speeds things start to get a little sloppy but just like there's a little play. As long as I'm driving straight. On the interstate over 70 if I hit an overpass I get a horrible wobble so bad I have to hit the breaks and get over to the shoulder. Obviously I haven't been back on since this happened, I changed my sway bar links and bushings but still feel the wobble slightly enough I haven't wanted to test it on the interstate.. Ball joints? Track bar? All seem fine but I'm still a green horn comparatively. Any help would be appreciated thanks

 

I had a Ford F150 that did this. After a few seconds of crawling underneath the truck I noticed a 1/4" gap in my drive shaft to rear axle. Two out of the four bolts were backed almost completely out. Tightened back up and vibration went away immediately. Just a thought.

 

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Driveshaft causes vibration not wobble. Different issue. OP, alot of threads on this issue. Worn steering parts. Have someone turn steering wheel with you under jeep