On a cold start my 2018 XLT when shifting to reverse, the tranny will slam into gear to the point that it will actually lurch backwards if my foot is not firmly planted on the brake. I got 16k miles and I just noticed this behavior about a month ago or so. Now, usually the rpms are still running at 1100 or so. I have been waiting for the truck to idle down before shifting, usually 30 seconds or so.