Drivetrain Grumbling- Again

Hi guys, sorry to put this up again but neither i now my mechanics can find the source of the problem, the vehicle is a '92 110 tdi hardtop with 175k on the clock and standards rear salisbury diff:
Basically, when i'm driving above 50mph and take my foot of the throttle there is a loud grumbling noise coming from under the vehicle. I checked all the uj's and halfshafts etc and everything seems fine- there's also surprisingly little play the props when turned by hand. So i took it to my local independent Land Rover Specialist, who found that the bearings in the rear diff were knackered. So they replaced all the bearings and refit everything, but it has made absolutely no difference. They are now pretty much out of ideas- having looked at all the usual suspects, and i'm pretty much out of money. So any ideas would be greatly appreciated.

Cheers,
Steve

Input/Output bearing in the T box?

G

Cheers- i'll check that

Steve

always worth removing the props and checking the UJ has free movement in all directions, difficult to spot a sticky UJ by just prodding at it with a pry bar

It turns out the garage in London that fitted a UJ a while back didn't bother to mark the Prop, so put it back in wrong and it was unbalanced. GRR.

Thanks for your advice though,
Steve