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Old 07-30-2015, 04:59 AM   #1
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Violently Shaking at Speed

I've got new suspension, poly bushes, and new-ish tires with straight rims. Over the course of commuting every day, a shimmy has developed and worsened considerably with time. The whole car shudders from left to right in rapid oscillation---not just the steering wheel, which also shakes.
I replaced the driver's side diff bushing and seal recently and that helped for a few thousand miles. The wheel bearings are tight as well, and the axles don't seem to have any play.It does not shake on acceleration, and if I coast down the highway in neutral it is arguably worse.
What might it be?
Thanks,
-Cm
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Old 07-30-2015, 08:10 AM   #2
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Did you try swapping wheels around?
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Old 07-30-2015, 10:39 AM   #3
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I had similar symptoms and couldn't put my finger on it because I had recently done wheel bearings, ball joints, axles and had an alignment. I took it to a professional wheel and tire place and had another alignment done. This solved the problem and now the car is smooth on and off the gas at all speeds; 70, 80, 90+

The place that did the previous alignment did a horrbiel job or did nothing at all. It needed to be done by a reputable business that specializes in alignments.

The only other thing I can think of is a sticking front brake caliper and/or a warped front brake rotor? Does the issue come and go? I experienced syptoms like this on my 9000 years back and it was a sticking front caliper+slightly warped rotor. Short story: I was doing 85 on the highway and missed my exit. I got off at the next exit, braking late and very hard before taking the overpass to the onramp and then back on the highway, accelerating quickly. The violent shaking in the entire front end, especially the steering wheel, started at 50mph and by the time I hit 80 it felt like the front wheel was falling off.

Hope this helps. Good luck.
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Old 07-30-2015, 10:43 AM   #4
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Check for a bulge in any of the tires, or tread separation. Tires can take awhile to fail but shake like hell while they fall apart.
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Old 07-30-2015, 10:55 AM   #5
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Have your wheels re-balanced on a road force machine. I tracked down a vibration for quite awhile until I went to a shop that had a hunter road force balancer.
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Old 07-31-2015, 05:28 AM   #6
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I just took the front wheels off to have a visual to make sure everything was tight and to see if there was evidence that might point to a problem. When I put the wheels back on, the shimmy largely dissipated. I definitely need an alignment as I jumped the car off the Belgian block on hungtington avenue in boston and pac-maned a wheel :/
-Cm
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Old 08-04-2015, 09:58 PM   #7
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Had a similar problem. Violent shaking that would be better at some speeds, but really bad at others. Also loud noise. You say you checked for movement in the bearings, but that's not exactly full proof. Check to see if the noise gets better or worse by turning different directions.

If it's a bearing, it'll get better by turning one way vs the other. Mine was driver side.

If it's the driver side bearing, the noise will get better while turning left (this is due to weight shifting via centripital force) and the same for the other direction.

Definely check all the other things though too. alignment, tie rod ends, brakes, and tires are all good things to look at.
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