I have a 2012 Sierra 2500 hd, gas 6.0, auto transmission. I tow an 8000 lb fifth wheel. The truck pulls the trailer well and generally shifts through the gears fine, with an exception. When I stop in a rest area on the Interstate for a few minutes I shut the engine off. I then go to leave and accelerate on the entrance ramp. The transmission seems to hang in (I think) third gear. Most of the time, it is on a level surface and the truck is accelerating as I would normally get on the Interstate. The tachometer is at 5000 rpm, I let off the gas some to let it shift and it doesn't. I then get back on the gas to about 5500 rpm and it finally shifts. Since this only happens as described and otherwise drives fine, it has just been a minor concern to me. A couple of months ago, I got my oil changed at the dealership and I mentioned this to the service writer. He told me that since it only happens intermittently, that they probably couldn't duplicate the problem and he didn't know what it could be.
I am now within several hundred miles of being out of warranty and I will be making an appointment with a different dealership. I was wondering if anyone else had similar problems.
