Ok here's my problem,

I have a 2007 FX4 Scab. About 8,000 miles ago I put on my 6" Fabtech lift (the basic kit) and added 35x12.5 BFG MT. When I would approach 55mph the steering wheel would shake, but when I got closer to 70mph it would smooth out again. The shop that installed my lift said I needed a steering stabilizer to correct the problem. I didn't buy a steering stabilizer, but when I upgraded my gears from 3.73 ti 4.56 the shaking stopped at all speeds. It was smooth as can be until last week when I got my tires rotated. Now the steering wheel is doing as it was before, shaking at 55mph. The shop checked the tires for balance whem they did the rotation and said it was fine. This is the second time I rotated these tires in the 8,000 miles. I did notice a little cupping on the inside tread of the front two tires before this most recent rotation. Could it be the fabtech shocks? I would think they woulld last more than 8,000 miles. What do you guys think?

Thanks in advance

 

Got an alignment this weekend and it fixed the problem.