When I shift into 4 wheel drive every.thing is fine. Until I try. To turn then there is this loud popping noise I'm trying to figure out what it may be. There's a little play in one of the universals. Could this be the issue? If anyone has any clue please help me out. Thank you

 

Poping when turning is a sign of a u joint going, you should go ahead and replace both

 

First order would be to replace u-joints. Check your hubs/ball joints as well, if you have to do either of those, it makes sense to only take everything apart once.