whining transmission

[oakeedokee]

I've recently noticed a whining coming from the transmission on my bobtailed RRC. Unable to locate by ear where the noise is coming from I had a look underneath and noticed a lot of freeplay in the rear diff. If I rock the rear propshaft left and right there is noticeable movement of the dirt shield at the diff. I presume there should be no play there at all. The noise by the way sounds like my Grizzly claws on tarmac but much louder.
 I've drained the oil and pulled out the halfshafts but haven't gone any further yet this evening. I should point out that I have a Detroit No-Slip fitted in the back.
 Is there any thing else I can check, maybe while I've got the rear prop off, putting the front axle on stands and putting it in gear with engine running so I can get a better idea of where the noise is coming from. It is a five speed with Borg Warner viscous coupling by the way.

[Difflock]

Rear wheel bearings ????? or diff bearings poss,Hope its the former

[Range Rover Blues]

Sounds lke the diff pinion bearings have gone, I've had this happen at speed and don't advise pushing the car untill it's fixed.  It's a diff rebuild BTW, if you are DIY I'd suggest getting a solid S/H diff and rebuilding your core into that.

[oakeedokee]

Wheel bearings are fine. Thanks RRB, I was hoping you'd confirm my suspicions. Right, diff's coming out tomorrow, I think I might send it off to this guy http://www.crowndiffs.co.uk/ he sounds like he knows what he's doing. Anyone got any experience of them?