1976 w100 powerwagon issues

Hey all, I just got this truck I mentioned in the title, and now that I've got the front driveline on its making a knocking noise when I drive it. I also can't get it to go into low lock or high lock. Any suggestions? I believe it's in the transfer case but don't know what I'm looking at...
In the end if I need a new transfer case, would one recommend getting a replacement all time 4wd or would it be any more benefit besides the obvious to get a part time one to put in? Thanks all, any ideas and advice are appreciated!
Author: Kilpack