I have a 2013 3500 with the Aisin transmission, 3.42 diff. and 20500# tow rating and I wouldn't want it any other way. With the Aisin you get 850 lb ft torque.
I'm not sure whether it's available in the 2500 Ram. You want the torque to overcome the low diff. ratio, it sure gives you decent fuel mileage when not towing.
To my knowledge the Cummins still puts out 800 lb ft when hooked up to the standard automatic transmission and that is still pretty good but I'm not sure if 17800 # in tow would be pushing it for 3/4 ton.
2013 RAM 3500 Dually Longhorn
2014 Trilogy 3650RL, W/D, Onan 5500, 8000# Axles, IS, 960 Watt Solar, 6x6 Volt Battery Bank, Freedom SW 3012 Inv/Charger