2013 subaru outback differential troubleshooting

Over 40mph I hear a hum/whine while accelerating. I put the car in drive while it was on jackstands and found that one rear wheel spins more slowly. I wonder if this is a wheel bearing, diff or cv joint problem.

[johannapoder]

all mighty brain has lost it. prolly holds the brake on

[WhatWhiteMenSay]

i have the same issue but my front dif on my 2014 wrx. driver, both rears spin easy. but my pass front spins slow or doesn't spin at all

[shaunhamilton]

Is that oil leaking on the pinion seals bad? I have the same thing

[thedudeabides]

I get that same whine, except in the front. Did you figure this out?