14LTZ-1LZ

Sounds (shuddering) like your TC is going out or is already gone, that's how my 14 LTZ sounded until the transmission went. Just got it replaced under the extend warranty I bought. Have them drop the pan and see if there metal shaving in the pan. If it's still good replace the trans fluid with AMSOIL trans fluid. Good Luck.

After I got the truck back took it for a drive you could say 122 miles round trip. Keep an eye on the trans temp. I guess I didn't pay attention before, but on the trip the temp. gauge reach 199 is this normal?

OK, thank you for the advice. I will have to look around my area for someone to tune the transmission.

It will be still under warranty for 3/100,000. What kind of tune do you suggest?

Transmission went out on my 2014 LTZ 4x4 109856 miles. before Christmas, no codes or of any signs of trouble. Out shopping with the wife on the way back home from Kansas City. Pick up started fine no service lights or trouble lights of any kind. Drove for a bout 10 miles all of the sudden would rev. high no forward motion would just coast. Pulled over on the highway thinking it was just a fluke, turn it off and started the vehicle again drove fine for a mile. Then it totally went out, check transmission to see if it has fluid, it was where it supposed to be on the dipstick. No leak underneath, but had a weird grinding noise from underneath near the transmission. Everything else was working fine,engine running smooth, heater and radio. Transmission temp. 196F, but still no forward motion. Called USAA which I might change my vehicle insurance or add AAA would only towing up to 16 miles paid for the remaining miles to the dealer which was 130 miles away. Flat bed came and towed to the dealer, which where I had the vehicle serviced 10,000 miles ago. Had bought a extended warranty that covered all that's mechanical. Took about 1 week for the insurance company to the make a decision to replace the transmission. Yes, they found metal shaving in the pan but still no signs of transmission going out, so am getting a re-manufacture transmission from GM with a 3 yr or 100000 miles warranty. Now my question is what's the break-in procedure?

This happened to me the dealer replace the "Brake control Switch" message has not returned. You might want to hold on to that module their might be nothing wrong with it. https://www.rockauto.com/en/parts/acdelco,22822675,trailer+brake+controller,14161