I have a 2014 and my was doing the same clunking sound. I had read something in one of the forums that this was a rear spring issue ( not matching) . I took my truck to my dealer and ask to speak with the shop manager and explained to him my issue., he directed me to his shop foreman and we took a test drive ( not a long one ) he told me that their have had other trucks with the same issue and that there was an order to try to make the clunking disappear.
1: tighten everything and grease the springs
( if that doesn't correct issue)
2: change brackets and (rubber half ball on spring)
( if that doesn't correct issue)
3: order new springs
Well the shop foreman said he wasn't going to make me take my truck back 3 times for the same issue and skipped to step 3 ordering me new matching set of springs.... This fixed the issue and I have not heard a single clunk