Transfer casephenomenon

[MuddyRangeRover]

Ok, so I just spent the better part of the day working on my Buddy's D1. As with all non offoraded D1's, his T-Case knob was stuck. Anyway, after remvoing the center console, spraying it with penetrative oil, and using pure brute force, it began working, BUT it only goes H-N-L. We can;t get it to go into Diff Lock (to the left).

We tried from H-N-L, wit no luck. Are we missing something here? What is the proper procedure for going into diff lock?
We tried while driving the truck and so forth, nothing.
Needless to say he is pretty pissed.
Any help is appreciated

[01001010]

I just kept at it when I got mine. Mess around with it, spray some more PO on it, mess around some more, then more PO, and later keep messin around with it....eventually the gunk thats built up down there will give and you'll be able to lock it...unless you want to continue disassembly and get RIGHT to it...its the faster method but requires the most amount of work.