DBTravelers

When pulling my 8000# travel trailer last year with my 2013 5.3 GMC 1500, I saw the temp hit 215 and was worried. Traffic was stop-and-go in 100+ degree heat. I tried finding out what temperature spells trouble in various forums, but finally just called the GMC dealership and spoke with the manager in the transmission shop. He said I would have to be up around 285 degrees for several hours of driving to start doing serious damage to the transmission and burning the fluids. He said today's engine/transmissions can run 220-230 all day long with no real issue or damage. Pulling the same rig last year in Wyoming and Colorado, I saw the temps hit 230 but only until I reached the summit and it cooled back to about 200 headed down the other side. No problems whatsoever.

Southpaw, I had a 2013 1500 Sierra with 5.3 and used Tow/Haul on it quite a bit as I pulled a 8500# travel trailer. I would push the button to engage T/H mode when starting on an incline, or if I needed to move into traffic a bit quicker than normal. I also used it in the mountains of CO, WY, and OR on a recent trip when the terrain was undulating. Other than that, I just let the computer take care of normal shifting and had no issues at all. We pulled across Death Valley and tranny temps hovered about 200, but that is not a problem. Traded for a 2015 3500HD Allison DRW, so until we trade for the 5th wheel we don't use T/H much yet. Congrats on the new 2500HD! Yes, we would like to see a photo of the new baby.