300tdi discovery front end rumble

Hi all
Over the past months a rumble has been getting increasingly worse from I am convinced the front axle/drive train.Some days the ruble is more pronounced when some lock is applied to the left at speeds over 40mph -other days the same noise but only when turn slightly to the right .There are no odd bits of metal etc in axle oil- the cv joints dont click on either lock, there is no play in the front propshaft or joints. There is no play in either front wheel bearings. All ball joints track rod ends etc have been replaced as thought it could be metal to metal on a worn out bush transmitting road/wheel rumble. Dont think it is the transfer box or gearbox because if you knock it out of gear the rumble is still there.No undue vibrations thrugh the gear stick either.
Anyone got any suggestions before i pull the diff out and replace it? thats all i can think it can be -bearings in the planet wheels perhaps?
Anyone got a good but inexpensive diff too?

post in the discovery section.

Just cuz this section sounds a bit like yer screen name, it's not much help yer question being in here! Like Spud sez, stick it in the Disco bit.