Tire Noise vs Wheel Bearing (or something else)

[ebod]

My father-in-law's Lexus makes a humming/droning noise that is very noticeable from about 30mph up. The noise varies with vehicle speed, not with engine speed (sounds the same at a given speed regardless of gear, even if coasting in neutral). The noise sounds almost like gears revving slightly after a downshift (but, again, the noise is independent of engine/transmission revs).

Ordinarily, I'd think this was tire noise, but he just replaced all four tires and had the truck aligned. The noise did NOT change between sets of tires (which were different brands and neither was an AT or mud). Also, the noise does not change based on road surface. Another thought is that it might be a wheel bearing (even though its more of a hum/whine than a crunch)?

Anyone have any thoughts on what this might be? If we have the tire shop mount different tires (different brand) and it still makes the noise (at which point the noise will have been present for three different kinds of tires), does that eliminate tire noise as the issue?

Thanks in advance for any suggestions.

 

[sum4all]

If you can, lift one wheel at a time and with both hands grab the tire and move it toward and away from you, alternating right and left hand. If there's play, then the bearing is going bad. I won't be surprised if the tire shop didn't notice it. Usually they won't try to do it because it's more labor intensive than just replacing the tires.

 

[hoser]

Inspect driveshaft u-joints too.

 

[arbetrader]

You need a vehicle lift for this, but the easiest way is to put the vehicle in the air, and give it a little bit of throttle while putting a stethoscope onto the backs of each wheel housing. You definitely hear it if it's a wheel bearing issue by doing that.