"a tow/haul switch so I probably don't have it (but then I'm not likely to be towing"
Tow/haul isn't just for towing. It's very useful on a heavy vehicle such as a MH up and down hills. In fact when I'm not towing and climbing or descending the Sierras or Rockies it's "on" just for the Tahoe.
Chevy manual says: "The Tow/Haul Mode adjusts the transmission shift pattern to reduce shift cycling. This provides increased performance, vehicle control, and enhanced transmission and engine cooling when driving down steep hills or mountain grades, towing, or hauling heavy loads."