I’m loooking at a used 2016 shorty Expy ( only 31k miles), w/ HD tow package, 3.15 yes electronic brake control, too. Why put such a 3.15 gear on a towing Expy? Yes gas mileage, when not towing, but one seems they would want better performance when towing. As it has an HD tow package? What am I missing here? Does the twin tubes make up for this gear? With an electric brake standard on HD towing one would think it is for towing a travel trailer?! What am I missing? Or is this 3.5 HD tow with 3.15 exceptable to be an rv towing vehicle? Thanks for your thoughts