Whine (off throttle / engine braking)

[clipper]

I've got a whine (wife not in the car), but only when I come off the throttle at low speed and under light engine braking.

At higher speeds (above say 40 mph) or applying heavy engine braking it doesn't do it, but sometimes it just starts as speed reduces.

It doesn't seem to match the description of diff whine that I've read on here.

I'm thinking prop centre bearing, any thoughts?

[clipper]

Any clues ?