So this might be interesting. My 2013 AWD has developed a Humm above 40 mph. Quiet below that. I'm taking it to the dealer Monday morning. Mileage is about 42,000 so that's probably higher than most on this board.
I'll bet dealer has no idea what it is. Any guesses?

 

Tire wear?

 

I don't think so. Humm is from the rear. Rotated the tires and sound is the same. Also louder when on a sweeping turn one way than the other. Rear Differential I'm thinking.

 

Wheel bearing maybe. I had a 2010 RDX and had to change both wheel bearings at around 60 000km

 

Did you get a differential fluid change? I got code A16 at like 15-20k miles, and the rear differenctial fluid was code 6.

 

Yes, that happened 20,000 miles ago and was changed at dealer. Took the RDX in just this morning. I'll report back when they tell me something.

 

Here is the update. Replacing Left Rear Wheel Bearing. Of course the dealer does not have the part so maybe have the car ready Tuesday.

 

Just picked up the RDX and all is well again. Replaced left rear wheel bearing. Service manager said our RDX had the most mileage of any he's seen to date. 42,322. Has not burned a drop of oil between changes and those MID changes have been at about 9,000 miles. Nothing bad to report. Car is running as well as new in every way.