Humming from left rear wheel

[Subaru-Sam]

About 5 months ago I replaced the left rear wheel in my wife's 2013 Legacy because it failed inspection. At the time there was no noise in the left rear. after I replaced the bearing I was getting a humming noise coming from the left rear. I thought maybe the new bearing was defective, so about 2 months ago I replaced it with a new bearing. I still have a humming noise coming from the left rear, and it is driving me crazy. Does anyone have a suggestion as to what is causing the hum. Thanks, Bob

 

[Ecmbuster]

Have a shop inspect the rear differential oil and inboard bearing for the rear differential.