I just had an 4 wheel alignment done and now I seem to occasionally have a wobble in the back end when my son is in the car he is about 240 lbs. I took the car back to the shop and they said they could see anything loose. Does anyone have any ideas what might cause it?

 

Have you had the rear control arms replaced yet? The bushing go bad and then all sorts of odd things start happening.

Easy fix and the arms aren't too expensive now. The bushings can not be replaced w/o replacing the arms themselves.

Look around there were a lot of postings about this in the last year or so.
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Jaguar: Grace, Pace, and Space - Sir William Lyons

 

I looked at the Control Arms and looks like one of the bushings is gone. I am going to try and replace it and see if it solves the problem.

 

I had a wobble after a wheel balancing. In my case, I wire wheeled the inner diameter of the wheel so it is not too tight on the hub. I know it should be snug by design, but if its too tight the mechanic may not tighten it evenly and a wobble was created. It fixed the problem in my case.