Spiderwebbb

I bought this 2015 LTZ last year around this time and about 5 months after buying it I was going down the highway goin around 55mph in drive on a flat if not slightly downhill grade and it decides to drop into 1rst gear. Called dealer they said bad programming. They keep it for a week and give it back. Then about 5 months after that I get this clatter when putting into reverse like slack in the drive train somewhere. My thought is transfer case. Call dealer they say bring it in but I'm working on the road. Before I can get around to it there's another problem forming. Now when going uphill or under slight acceleration it shakes. The whole truck vibrates and shakes. I'm on my way home on a 12 hr drive and I. The middle of that drive while praying it doesn't leave me stranded the a/c just quits out of no where while cruising at 65. I've pulled a camper a couple of times and it ways a little over 7 but way under what it is rated to pull and I've used 4x4 in ice once and in mud a few times on job sites but nothing major and I've had it services on time every time. This isn't exactly what u expect when buying a $46,000 truck. Very disappointed and was wondering if anyone can relate to these issues