Mine is a '14 1500 Z71 4wd crew cab with 18,000 miles and its doing this bad. Its quite embarrassing to drive through my parking lot at work b/c its so loud it makes people stop and look. Been doing it for a while now and I can't tell where its coming from. I took the spare completely out and it still makes the noise. Torqued the leaf spring bolts, shock mount bolts and anything else I could find and still no change. When I shut any of the doors with a little force there is something under the truck that rattles but I haven't been able to locate it.
Now I have a squeak in the front area that is driving me nuts. It happens every time I any small bump in the road. I like this truck but its driving me nuts with all the noises. It will be going to the dealership shortly.