Okay everyone, I have a 1999 xj. I’m working on putting a 4.5'' suspension lift under it. It is my daily driver so a little at a time and when budget allows. I am doing the "Budget lift" I have put springs out of the front of an old F150 and I have air shocks in the back for now. So its not driving up hill to bad. I will be putting rear leaf packs from a Dakota and a SYE kit in ( its on order ) I do have a cv style drive shaft that was the front drive shaft from another 99 xj
That I will be using after the SYE kit is in. Now here is the problem. When I am traveling at 45mph or more, even the slightest little bump in the road will cause the jeep to shake violently! It jars your bones it is so bad... WOW. I have a snow plow that I will be using this winter that is what started the whole thing, but when I had the plow on after all this to date I didn’t have the problem as bad. I have taken the plow of for gas mileage and cooling and no snow.
I should also point out that I jacked up the front of the jeep, when I grab the tire I feel no play in anything, I also have no slop in the steering wheel. The shaking feels like it is from the driver side... Thanks for any help!

 

check your track bar bushings, bolts, tre, and frame mount. any play or wear in these can lead to dw. worn/loose track bar parts are the most common cause of dw. there are other possibilities but start there.

 

I had the same problem but what it came down to was a bad steering box. Spent hundreds in front end repair for bushings shocks drag link steering stablizar springs etc then I finally checked the box and it was the
Main problem. Change that and buy a steering box brace from Rusty's offroad.advance auto has em for $140 new and the brace from Rusty's is only around $70 w/ shipping

 

What you describe is often called death wobble. I agree that the track bar could easily be the cause. What type of track bar was used or what was done to compensate the track bar for the additional lift? Did you do a front end alignment? That caused death wobble on my '98XJ. There are lots of other contributing factors to DW so you might want to do a search on the subject to get started.
hth, Doug