All I need to do is go down a street at 40 + miles per hour, hit a bump or turn to the left just slightly and the front end shimmies violently. I have a brother that is a Ford tech and he tells me it is the tires that cause the problem. so I have tried different tires and they all do the same so I don't believe the tires are the problem. I have taken it in for an alignment and the don't find any thing worn out. So no matter what I have done in the years I have had two of the same truck they both did and the one I have still shimmies really bad.