This problem just started today..When I'm going highway speed, this shimmy starts. It's like I'm driving over the warning notches in the road on the side, without the noise.. I can make it go away by putting on the brakes, but it comes right back. It only happens at speeds above 45. I don't think it's the wheel bearings. Maybe something in the steering... When I jacked up the front, I have about 1/2 inch play when pushing the tire front to back. any help?? D.