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Q: Low hovering/humming (not high pitched) sound driving over 35mph.

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Whether accelerating, coasting, or breaking, the sound persists. Just noticed within the past few days. From forums, wheel bearing seems to keep coming up, but they usually refer to a "helicopter" noise, which this is not. Mine is steady, not choppy, and no shaking of vehicle. Any thoughts? I just want to be semi-prepared for what it might be (or isn't) before taking to a mechanic.

My car has 84000 miles.
My car has an automatic transmission.

Hello there, thank you for asking about your 2006 Chevrolet Malibu. Failed wheel bearings will not typically cause the vehicle to shake. They will instead make exactly the noise you are describing: humming. Although humming is typical, there are other sounds and frequencies that will occur depending on the failure mode. If the bearing race is really "destroyed" (pitted) for example, it’ll sound like you’re driving on a gravel road; the noise will be loud. Wheel bearing failures can mimic tire defects, including merely abnormal tread wear. YourMechanic staff will typically apply wireless chassis ears to the four wheel bearing positions. Using wireless pick-ups, a channel receiver set next to the driver will identify the wheel from which the noise is coming. You can ride along and see it for yourself. In some cases, though the bearing failure is so obvious that merely "loading and unloading" the vehicle suspension on a curve will identify the wheel position. Your bearings are bolted on assemblies so they are straightforward to replace; you need not worry. Also, for your application it must be determined whether the mounting bolts are re-usable. The FSM for many GM vehicles of your type states in huge print: DO NOT re-use the wheel bearing mounting bolts. That is because those bolts are typically tightened to 90 ft lbs., which is very tight, and when you start reusing a bolt already subjected to high stress, they tend to weaken and can fail in the field. At any rate, the first order of business is to rule out tire noise. Once that is done it is a simple matter to identify the wheel position. Also, if a front bearing has failed, you might consider replacing both sides as the other may not be far behind. Finally, buy the part from AC Delco. In other words, don’t get the cheapest one you can find, even if it says "guaranteed forever," which has no meaning insofar as the quality of the part. Another good vendor is SKF. If you would like help, a technician from YourMechanic can inspect the noise in your vehicle and make the necessary repairs.

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