Loud clicking noise in 89 front end

I have just developed this loud clicking noise in the front end of my 89 Sub. It only happens when I am backing up and turning (backing out of the driveway). I am pretty sure something is binding as I can feel it popping through out the whole truck. It got much worse today when we drove up one of the local mountains here. This time I was in 4WD and we turned around(3 point turn on the road). In fact it locked up the whole driveline. Before it was completely bound up I got out to see if I could hear where the noise was coming from. I was out side of the truck watching the front wheels while the wife was backing it up, I had her bring it forward to see if it was only in reverse when it wouldn't move. I got back in and pulled it out of 4WD and stepped on the gas and it still wouldn't move. It tried but something was bound up. At this point I was nervous about being stuck on top of this mountain so I stomped on the gas and it finally popped loose. Nothing broke it just un-bound (if that’s a word). On the way home we developed a leak.It was tranny fluid but I dont know if it is from the transmission or the transfer case. The transmission was still full so tommorrow I will check the transfer case. I dont know if these are related of if it is just my bad luck. I dont think they are related. Also, when I was watching the front end while my wife was backing up, I saw the right wheel was noticeably popping. I didn’t see if the left was doing it as this is when I had her drive forward. I am wondering if it is in the automatic locking hub somewhere or in the diff itself. I am not too familiar with 4WD systems so any help here would be appreciated.

Well, here’s an update. I checked the transfer case and it was FULL. I mean completely full! I drained out about 1 quart. After looking around and some cleaning, I found gasket maker so I am assuming it has been rebuilt. I am also assuming it was filled when it was laying flat on a work bench, which is the only way I can see it being that full. I hope that is where the oil came from. I drained the case and put new fluid in it. Did a test drive and no leaks so I hope I figured that out. As far as the noise in the front end, I am thinking it is the hubs. They are auto hubs and from what I am reading, when you back up they disengage and then re engage in that direction. Tell me if I’m wrong! I am thinking that is where the problem is as it only happens when I back up. I looked up after-market manual hubs for replacement as I don’t mind having to get out and lock them. Any body have any ideas on this?

Stop driving your truck!!!!!!!! The front U-joint is going out! It may and most likely will lock up going down the road and stop you from steering. I have had this problem before with an 87' 1/2 ton truck. I put it into the ditch, luckly I was alone on the way to work (my wife would have had a cow if she was with me!). The fluid might be the axle fluid leaking past the seals after you "broke it free".
Good luck!
Ingoldx1