Hum (rear end)

My 2010 is humming like bad.....I think it's the rear. the faster you go, the louder it is. Put new tires on - same noise.

I've lost almost 10 MPG.

Dealer checked bearings - said they're fine. Tech used stethoscope. He did hear the noise during test drive, but couldn't locate the source, and I couldn't sit at the dealer any longer without going mad.

anyway - anybody have a clue? I'm thinking about doing the rear bearings anyway....

 

Autonation Toyota in Centennial, CO looked at the car - heard the noise, found no issue.
This weekend - I grabbed a new hub, and popped the wheel off (with a good friend, who is a much better mechanic than I am).
anyway, the second we started pulling the brake caliper off.....we realized it was a dragging brake pad (inner pad, driver side rear).
The lower slide pin was locked up....and needed some torch time to break loose (otherwise, I was staring down a new caliper assembly....which aint cheap!). Got the pin broke free....the rubber boot at the end was gone, and the pin was pretty rusty. All of metro denver (including 2 toyota dealers) do not stock caliper pins. Go figure.....dealer couldn't figure this out?

anyway - soaked the pin in PB, sandpaper to it and the pin cylinder......and the pin is sliding nicely now.
I will order a new pin (and boot....since the heat did a little damage to it). So......all that heat and noise was in fact from a dragging brake (as xliderider suggested).

also worth noting......the little expansion springs (to retract pads off rotor) were non-existent. they're installed now, though!