Just noticed a noise like a humming coming from the rear axle when i turned my radio off. It gets higher in sound the faster you go its not loud at all but something i have never noticed before.

If you dip the clutch when moving its still there and if you accelerate and back off the note doesn't change, its seems that its in relation to road speed.

Is it the diff, or is it a normal 4x4 sound ??