I don't use the 4WD much but whenever I did I kept hearing a clunking noise when I made a turn in 4WD. Didn't matter-4W Auto-4W Lock-4W Low.They said that it was normal on a hard surface. Okay, but it did in my field in sand as well. Finally talked the dealer into checking it out.
I really don't know what the problem was. When I picked it up today they said it had a leak and the bearings went out. BUT. When I had the oil changed the week before and complained again about the noise they said they checked the fluids in both differentials and they were clean and full. And- I don't remember when it didn't do it. I have had the truck since it was new.