Kilpack

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!

04 Diesel

Are you sure the knocking is not a bad u joint? Your 203 transfer case linkage might need to be adjusted, also hav you checked if it has enough oil in it. When I buy a new to me truck I always change all the fluids, you can tell by how dirty the fluids are if the truck was taken care of.