F350 Super Duty vs 3500 Denali vs The Ike Pulling 30k lbs

To have zero brake applications they need to be running at the speed they want to maintain then set cruise to say 5mph less but also lock the trans in the same gear you would have climbed that grade in. This will vary based on the grade and load. This takes a human to dial this in.

I easily maintained 30-35mph locked in 2nd gear on a several mile 14% grade at 33k combined simply by moving the cruise speed up or down with my thumb.

For the Cummins closer to 3k will give the best downhill braking.

Cool brakes along any big downhill grade = GOLDEN.