Facts: 1994 Buick LeSabre has violent shimmy at virtually all speeds. I just spent $820 to replace both bearings (this one has front wheel drive), half-shaft axles, turned rotors, balanced and rotated tires. No luck. Two Buick dealers say they are baffled. It shakes so bad on good highway even that I am becoming afraid to drive it. Odd, tho, on fairly hard left-right curves, the shaking stops. Any suggestions?