My 2015 LTZ behaves just like this. Had the seat clip fix done a couple weeks ago... waiting to see if the issue appears again or not. I've probably lowered the seat my maybe half an inch at best. Mine too, has the rear noise issue in the cold. This happens mostly just when turning a corner from a standing stop, and seems to be coming from the left right part of the truck. I haven't complained to the dealer about this yet, as it often isn't cold enough on successive days down here in Florida. Too late this year. Will see if it re-appears next year when it's "cold"... under 45.