I still say it is a combo of excessive clearances with transfer case output needle bearings and slip joint wear being the root cause.

I've looked and nothing seems to be loose. If I knew some of the common loose suspension points I could give them a thorough going over. Also, you can see where the bump stops are hitting, maybe this is also caused by the same problem? I understand they are too prevent the body from bouncing all the way down but I haven't bound the suspension up or hit any serious bumps.