Last summer on I40 headed east thru North Carolina. East of Asheville there's a very long decent. Flashing lights, all truck pull over and such. Towing a Honda Accord with a Ready Brake tow bar. Top of the hill hit the brake for a bit until the transmission down shifted and the coach held steady a 55 or so the entire decent. Never touch the brake again. RPM peaked at about 3500. Bottom of the hill hit the resume on the cruise control, transmission up shifted and the coach accelerated up to my normal 62 and away we went.