80 Series Land Cruiser - Knock noise in diff?

Hi,
I experience a knocking noise (sounds exactly like a crook cv joint) in my front diff when cornering, but only at initial start off. It happens in forward and reverse. I had the vehicle in a garage to have the cv type joints replaced but upon removal and clean-up they show no signs of wear after 296,000 kmh. A faulty bearing was found to be spinning on the hub and was replaced (hub & bearing) {caused by mixture of different greases over the years}.
Has anyone ever encountered this problem? and if so what was the solution?
Could it be a noise transmitted from the clutch as it happens when the clutch engages with the engine ie doing a U turn from stand still (happens when turning left or right). The noise gets more severe as the revs increase and stops knocking while depressing the clutch to change to 2nd gear and re continues to knock until wheels are positioned for straight travel. No noise or vibration is felt through the gear stick.
It has me stumped. Any relevant suggestions will be greatly appreciated.
Cheers,
Chris.