My 2012 had a roaring noise from day one. I took it to the dealer with a few K miles and they replaced the entire differential. They said GM wanted the entire unit sent back to them. So they didn't even open it up.

After the new unit was put in, it eventually started roaring again or at least I thought it did. It wasn't sure until my 2013 arrived that I realized the rearend on the 2012 had actually gotten very loud. By that time the 12 was at auction and had sold.