My mechanic confirmed the wheel bearing in about 30 seconds driving at highway speed. Says it is front left, but I'm having him do both b/c I don't want to drive around listening for the other side to go bad. I suspect this repair is in my wheelhouse, but I prefer not to do my learning on the crown jewel of my fleet. That's what the Spitfire and Passat are for.

FWIW, another description of the sound was that the car sounded like it needed to shift up to another gear. I didn't describe it that way b/c I didn't believe that it was related to the transmission since the noise was speed, not rev-related. But during the test drive before we got on to the highway, the mechanic relayed a story that he just did a bearing on an A6 and the owner brought it in suspecting that there was a problem with the car not upshifting.

That was really what it sounded like.

 

Another method is as simple as just spinning the wheel when it is up in the air on a lift. Although there is no weight on the bearing you might still be able to hear the grinding of the worn bearings in the hub. A Stethoscope might also help when listening behind the wheel at the hub.

 

"Yeah I am not in love with the wheel bearing hypothesis, so I appreciate other suggestions/ideas."

How you feeling about it now?

 

Assuming it is confirmed when the bearing(s) gets replaced, I'm super happy that it turned out to NOT be one of those 'nut on the wheel' problems. They pop up all too frequently with me.

 

Putting this thread to bed. Got both front bearings replaced today; one that was needed and one that was PM. I asked the mechanic to show me the old ones and sure enough, the bad side was hard and grumbly when turning it. Didn’t really need the good bearing for comparison, but with both of them side by side it was really obvious. Replacements came from SSF autoparts https://www.ssfautoparts.com/

Thnx again for those who participated in the discussion, and my sympathy to pk4144 who made comments just before the carjacking. Also, +1 that pk4144 and GF didn’t get hurt.