I would think that you would know a wheel was bent when trying to balance the tires. And if it was something like a bent wheel, wouldn't it shake a little at any speed. It is most likely a bushing or some other part that at a certain harmonic shakes violently. My Ranger has a bad shake from time to time. But that may have something to do with the fact that the piviot bushing for the right beam is all but gone. Keep in mind that the shake may not be in the front at all.
Tony
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