Transfer Case?
 

2007 Chevy Silverado 1500 LT (newer body style). I was driving down the interstate and heard a slight whine from the front followed by a slight deceleration. After a while down the road there was a loud bang from the front end. I immediately pulled over. I put the truck in both drive and reverse and heard a grinding sound from the front end. I looked the best I could being on the side of the interstate with below zero temperatures and it looked like smoke coming from transfer case. Anyone have an idea what I'm dealing with?