shakes when you hit 50mph

I have had this problem for quite some time but I finally figured it out. At first I replaced all the brakes. Then a mechanic told me it was probably the front calipers so I replaced those. That didn't help at all. I called a friend over to look at it who also has a jeep. He jacked it up so he could look under the front. He got down on the creeper and grabbed hold of the TRACK BAR to pull himself under. Immediately he said the track bar was loose. I got under and felt it. It was loose but I really didn't think that could be it. I felt the track bar on his jeep and it didn't move at all. Anyway, I replaced the bushing first only to find out that the (ball joint) like piece on the other end was worn out as well and then had to replace the entire bar. $52 at my local parts store. Haven't had any problems since. Replacing the TRACK BAR is super easy and only takes about 20 minutes. The hardest part is removing and installing the end on the driver's side because it is hard to reach and is a castle nut with a cotter pin.

Have the front tires and wheel balance checked. If it is OK, then have the suspension and the axles inspected.

looking for same answer i've replaced everything but trailing arm bushings.. i even went out and got new tires, the funny thing is it will do it intermitantly not all the time and when it does do it, you slow to aprox. 30 mph it goes away, what is the problem?