There are 3 versions of the 6.7L Cummins.
The 6 speed manual trans equipped trucks get one rated at 350hp/660tq.
The trucks equipped with the Chrysler 68RFE auto trans are rated 370hp/800tq.
The trucks equipped with the Aisin 69ASC auto trans are rated at 385hp/850tq.
In other words, the Aisin is the heaviest trans available in a Ram truck. In 2008 - 2012, it was only available in the 4500/5500 trucks, and had an OEM warranty to 180,000 miles in those commercial vehicles. Should be pretty stout.
The DEF has proven to be no big deal. All of the big 3 diesels use it, and most people get 750 - 1000 miles per gallon of the stuff.