I recently installed a Rough Country 4 inch lift on my TJ. I am experiencing vibration issues now from 1st to second gear on the lower end of accelerating. It's only noticeable then if I take off full throttle. Under normal acceleration you don't feel it. I replaced the u joint closer to the rear differential. The front doesn't seem to have too much play either. The transfer case drop was installed also, only thing I didn't put in was the 4 wheel drive drop bracket. Tires were recently installed an balanced with used tires. Also didn't have an issue with this till I had a front end alignment.