Rear diff noisy?

I have a whine coming from the rear I think, its loud in my 90!with exshaust and tyres any way,

It's only there a 1/2 to 3/4 throttle in any gear,

Holding steady speed and there's no noise,

Coasting or slowing down on over run, same nothing not a noise

I think its the rear diff, I would just replace it with another I have around but I'm lacking time and would need to build my arb into it,

Could it just be the back lash not set right? I've used the Landy more in the last month than the last 6 months as it's been parked up,

I've tried the changing oil in the diff, I did the transfer box oil not that long ago , all the wheel bearings are good, I don't think its the transfer box but could be

back lash wont be out unless some one who doesnt know what they are doing has messed with it or bearings are worn, pinion bearings generally show on over run as large cw is the driving small pinion, you could remove sump on t/box and try with rear prop off

Might pull the rear diff, there's a little play in the input and every other time now and again my arb leaks, that's what made me think so thing might have moved inside,