Wife called me from my parents' house a few hours away and said on the way down there she was hearing a high-pitched whine "from the back" of her 2013 CX-9 (AWD). I figured "oh, wheel bearing probably," but after getting down there and test-driving, here's what it is:
- Not terribly loud - my years of metal concernts maybe make it harder to hear for me than my wife (and all my loud cars), but it's kind of a dull high-pitched whining noise. I would consider it "faint" but my wife says she can sometimes hear it over her music (admittedly, she doesn't crank the music).
- Only happens at speeds around 50-60mph or so - or at least that's the only speeds I can hear it at. The area down there isn't really good for going any faster. Only seems to happen once the car has been driven for 10-15+ minutes, but even then seems a bit intermittent - like it goes away for a bit if you come to a stop, then comes back after you get back up to speed.
- Only happens in 6th gear. If I put it in manual shift and downshift to 5th, it instantly goes away. Doesn't happen in any other gears or other speeds.
I only found one or two references to a problem in a CX-9 matching this description but neither had a follow-up or resolution.
The vehicle only has 68k miles, and is used predominently for local driving. I doubt it has ever had its ATF/tranfer case fluids changed, but obviously that's what I'm going to do once the car is back home.
Otherwise, I know precisely jack about automatic transmissions and what could make this noise. My guess would be some kind of bearing, but really hard to tell. So, any insight into this specific transmission or noise would be helpful. In the meantime, i just told my wife "shift down to 5th if it bothers you that much" lol.....
