I have a nasty knock coming from behind me when on full lock (or a lot of lock) either way while going forward. Almost certain it's a rotational knock.
Crawled under and had a look around and noticed that the centre diff mount was broken and the diff could move around quite a bit.
Replaced that but the knock is still there. Any ideas where to look next?
Did the owut test, got about 45 seconds for 5kg at 1.2m when cold (for about 90 degrees). Don't notice any noise or braking from the vcu when in reverse on full lock.

Thanks

Give the driveshaft joints a rattle around by hand and check for play. You've done the obvious one !
Check diff oil too while you are under there!

After a bit more investigation the two prop bearings either side of the VCU were gone big time.
Replaced them and it's all back to normal now, no knocking anywhere.