Thread: Rear diff whine

So out for a hunt this morning and i noticed that as i hit around 3000rpm i start to get a buzz/whine from the rear. This would get worse as i accelerate up to 3500rpm to more of a high pitched whine. No noise when I am coasting or braking. I'm assuming its a rear diff issue?
Truck is a 96 3rd gen Surf 2.7 petrol auto.

Any thoughts on it as to my next move with it.