Engine mounts can cause this but there are other suspects too. You didn't say if that vibration is in the steering wheel or you feel it in the pedals. If an engine mount has collapsed, it will let the engine hang low on one side. That changes the geometry of the drive train, which changes the length of the half shafts by a fraction of an inch. Very often wear takes place inside the inner cv joint housing where the three large rollers run back and forth. Anything that changes the length of that shaft causes the rollers to move to a slightly different area and roll over the edge of the worn spot. Under the right conditions, usually related to load on the engine, the rollers will bind and not roll freely over that ridge. Instead, the shaft pushes and pulls the spindle and transmission together, then apart. Since the spindle is bolted to the lower control arm, which is mounted on rubber bushings, the entire suspension system gets shoved back and forth a little. The steering linkage is connected to the struts or spindle so that will vibrate too, and you'll feel it in the steering wheel.
On some cars, due to the design of the steering system, there's less tendency to feel the vibration in the steering wheel. You'll feel it in the whole car from the engine and transmission vibrating back and forth. In this case there's actually two causes. The first is that wear in the inner cv joint housing, but that will often go unnoticed until a second cause makes those rollers bind.
The more common symptom of a worn cv joint housing is a shaking in the steering wheel from 0 to about 35 mph, when accelerating and turning, as in when leaving a parking lot.
One other thing to look for that only applied to Ford products, and mainly older ones, is if the car has cast aluminum wheels with a factory-installed locking lug nut, those nuts were so heavy, there was supposed to be a half ounce weight added across from it after the wheels / tires were balanced and installed. Because the lug nut and weight were different distances from the center of the wheel, they each set up a vibration at different speeds, but the thinking was the weight would lessen the vibration in the speed ranges where you were most likely to feel it.
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Wednesday, January 1st, 2014 AT 2:23 PM
