Light throttle whirring noise 45-65 mph M6
 

Hoping someone can point me in the right direction. 2009 M6 base car, I have a whirring (bearing going bad) noise between 45 and 65 MPH. More of a whirr than a rumble. Sounds like it's coming from the trans or diff area. Only on light throttle, quiet on coasting or harder acceleration. Can easily make it come and go by slight changes to the go pedal. Seems to be getting worse over time. Car has 20K miles. Does it in any gear. Turning left/right changes nothing. Goes away above 65 MPH. Ideas?

It might help if you can post a video with the sound.

Technologically challenged on posting a video. I may have to consult a kid. :) Sounds like a noisy bearing on the output end of the drivetrain since it goes with vehicle speed, slightly chirpish rather than rumbly. Steady speed and it's there.

My speculations were output bearing on trans, a bearing in the diff, or something with the axle shafts. I know nearly zero about these car specifically, so just my general ideas. Was hoping there was something common and relatively easy. Emphasis on hope.

Well, have you tried to hear the sound, or any sound, with car parked, in Neutral, clutch engaged and disengaged? Trying to ID or eliminate the driveshaft guibos or bearing in the torque tube.

Sound only comes above 45 MPH, loudest around 55 and diminishes as you get to 65 or so. It is quiet in neutral coasting. It does not change pitch with the engine speed, only the vehicle speed. Feel like it's not before the transmission.

I should also mention it is barely perceptible the first few minutes you drive with the car cold, but comes on as the drivetrain warms up.

I appreciate you playing 20 questions, it's very hard to diagnose like this I know.

Mine does something similar, it's gotten only slightly more noticeable over 2 years, happens when letting off gas between 65-70, & only on a slight downgrade. Been told it's fairly "normal" by a few forum members & I honestly don't worry about it at all. My old gearhead sense tells me it's in the diff due to slightly increase ring/pinion backlash, maybe normal wear... diff fluid was good when I changed it, I just enjoy the drive.