On my Ram I can manually engage the exhaust brake and Tow/Haul mode. I always drive with the exhaust brake on and whenever I hook onto any trailer I engage Tow/Haul. The Tow/Haul mode does a great job of managing shifts when a load is connected and it also makes the exhaust brake more aggressive. Actually, the exhaust brake works so well I've had to tap the throttle descending a hill because it was slowing me too much...and that was towing a 13,000lbs 5er on a 10% grade :E
I figure transmissions are extremely expensive and Tow/Haul mode gives better shifting performance under load so I might as well use it.
KJ