I have a shimmy at high speeds. 0 to 70 is smooth as silk, however 71mph to 80mph or 85mph the shimmy is present (not bad all the time) at times worse than others. The steering wheel shakes left to right (not up and down) i can exceed 90mph and out run the shimmy! smooth as silk @>90mph.

New upper and lower (poly) bushings (6mos), new upper and lower ball joints (year). New pitman and idler arm 2 mos).

no visible loosness in the front suspension.
any ideas? replace ties ( probably orignal)

prob'ly tires or just wheel balance.

Most likely wheel balance. Aside from that, if the suspension linkage and ball joints are all in good shape, then the other possiblity is your steering gear box is worn and needs the lash adjusted to compensate for its age. It's a simple adjustment process that you should be able to read up on in any service manual (i.e. Chiltons)

I know you fellows probably don,t want to hear this BUT, I have a 65 mustang conv [you know for the wife and me to cruise around in on sunday afternoons] and if she is happy well YOU know what that means. Anyway the mustang shimmy,s also at about 53-59 mph and then it is gone also.I have noticed that it seems to do it worse on a long straight road that has alot of crown in it.I have gauged the tires up and that seem to help but it is still there, I have had the tires balanced 2 or 3 times and the front end aligned twice, any ideas.

Chevrolet used to call this phenomenon "smooth road shake", which can occur even with a perfectly-balanced tire. It results from a combination of lateral runout and radial out-of-round in the tire and radial force variation in the tire due to the location of belt caps and joints when the tire was built (which is why modern car wheels are marked for their high point of radial force variation and the tires are marked at their low point, and the two marks are aligned when the wheel and tire are mounted at the assembly plant).

The Hunter GSP-9700 wheel balancer has the capability to identify and diagnose both axial and radial runout, and the point of maximum radial force variation as well; use the link below for a locator for a dealership or shop in your area that has the GSP-9700, and let them do their thing - you won't believe the difference!

http://www.gsp9700.com/
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