To H303
I actually do have the 4:1 T-case and a rear diff lock (came like that from the factory).
What seems to happen is that when I try to drive it very slow (1500-2000rpm only) on such roads the front suspension is to hard (It seems not to compress enough).
This is causing me to NOT use the rear diff locker. Because If I do try to use it, the truck just gets thrown sideways.
I've attached a link to an off-roading I did in the Negev desert. At this video I also had to NOT use the rear diff lock. When I tried to climb with it set to LOCK, I got stuck on the begining of this hill you see in this video.
http://www.youtube.com/watch?v=4nz-_OO6qTA