Help: Steering / Front end shimmy over 60mph?

[Buggin]

Need some help here folks...

This started several months ago before I went to the desert:

Over 60mph, the steering wheel and entire car start to shimmy. By 75mph, it feels completely unsafe... and shakes violently. Mostly happens when coasting. Under accceleration there is only a small amount of shake.

Things I've tried:
1) Moved rear tires to front and balanced them. (lug bolts good)
2) Replaced both axles with brand new ones from driveshaftshop.com (axle nuts tight)
3) Had alignment done.

Possible concern. Rear tires (ones that originally were up front) are in need of replacement, so I have not balanced them yet.

I've searched through all the posts in the old forum and don't find much help. Most people never come back and post their fix...

[wldwsel]

I had a run of Firestone tires about 20 years ago that were separating the steel belts. Went through 13 new tires in 3 months (have never owned another Firestone tire since).

One of the many symptoms was a shimmy or vibration that was divergent (increasing) as a function of speed. Didn't seem to matter whether it was front or back.

Some of these tires lasted up to several weeks before they went bad, some were bad when I pulled out of the tire place, and one or two lasted up to two months.

Easy to look for.

Good Luck and thanks for your service to your country.

Wild Weasel

[ttupper]

Have you considered struts? Your struts are what keep your tires in contact with the road surface when encountering bumps. Hypothetically, if the struts are bad, they aren't recovering quickly or preventing the tires from lifting off the road surface when you go over variations in that surface. The fact that it happens increasingly more violently as speed increases would make perfect sense because increase in speed is equivalent to an increased impact force whenever the tire encounters a change in the road surface, and the greater the impact force, the greater the bounce back. With bad struts the tire then begins bouncing violently because it literally leaves the road surface with each bounce, and the corresponding return to the road surface just triggers a new bounce. Once this starts, it isn't stopping until the force (e.g. speed) is removed, or unless the vector of the shiftis changed by something like, oh... torque, which you get when you are applying power. SO that would explain why it is worse when coasting.

This is just my uninformed and potentially ignorant guesswork. In other words, it's just a thought - I would confirm with a mechanic before making any more major replacements.