Not sure on your chevy but on the new ford E series at least 2016 and newer the tow mode is great for hills. If you tap the break petal it will down shift 1 gear. tap again down another gear..... Also very helpful for stopping as well because you use your breaks and engine to slow down. I would use it all the time but my MPG suffers with it on.
My 2011 F250 does the same.
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