96coloradoxj

Usually shaking around 55 mph always indicates balance issues. So get everything balanced.

Tsaani97xj

I vote tires and/or balance like some others. I had similar issues and there are some threads around others have posted chasing the issue. Driveline vibes dont sound like what is being described. I eventually gave up because of time and money issues but the problem has resolved itself after several thousand miles and it now drives smooth. If your tires werent roadforce balanced that seems to solve this problem.

Best of luck.

sycoglitch

Did they replace the trac bar with a stock one or one for a lifted jeep?? Not maybe yea this issue may be tires but an improper trac bar will cause death wobble. And another easy thing to check is rotate the tires front tks back real fast. I too have see not just improperly balance tires but a bad tire itself cause shakes at 55-60 and disappear after that

JeepFan24/7

Yeah you got to always make sure your trac bar bolts are tight they tend to vibrate loose and make sure your tie rod ends not bad, these are some of the causes of death wobble which your mechanic referred to.