This is my first post here, and what a GREAT resource to find! In the end of August 2015, I bought a 2014 Silverado High Country as a 50th Birthday present to myself. the second day I drove it, I had all the windows down, and was coasting at around 20mph, and heard a very noticable metal-on-metal clunk sound when I accelerated again. I did more testing over the next several days, and took it to one of my good friends auto shop. He drove it with me, and easily recreated the clunk sound. He told me to contact the dealer. I made an appointment, only to have them tell me it's normal and provide me with the same serivce bulletin mentioned in this thread. This is my first ever GM purchase, and because of this clunk issue, as well as a drivers seat that moves around, and a salesman that completely lied about the vehicle history, I'm VERY dissapointed with my purchase..........