I have a strange "howling" sound coming from my 9" rear.

The sound is a low frequency "howl" and sounds nothing like the very minor conventional gear whine which I also have but is not a problem. I am confident this is not gear whine.
The howling sounds starts at about fades in at 40MPH then fades out around 50 MPH. The frequency of the howl is rather constant, its just the volume that increases then fades out.

Another notable detail is I hear the sound mostly on the left side of the car and only in my left ear. I do not hear the sound inside the car at all.
Does this sound like an axle bearing to you guys?

 

Axle bearings is probably the issue if you are sure it's not gear whine. If you can't hear it inside the car at all, how are you hearing it.

 

Driver side window up or down, it is most noticable through the left ear. If I turn to listen toward the interior rear I just dont hear it nearly as much.

 

bump

 

can you get it on a lift, run it up and listen in the rear with a mechanics stethescope. Should be easy to find