Apologies to the OP that this turned into a transmission thread. I'll summarize: Go with 3.92s unless you're overly concerned about fuel economy.there may be similarities to cooling the transmissions, but the two platforms do not share the same transmissions. the 2500 engines are mated to a 6 speed tranny
But to @Goatmann...there have been rumors shared about an 8-speed making it to the next-gen HD lineup, but I see two problems with that: (1) The soon-to-be-revealed 2020 "4.5 gen" HD is just a refresh, so it wouldn't seem profitable to make a change now, and (2) economy and emissions are not as important as durability in an HD powertrain. Have you heard anything about next-gen HD transmissions? What about @devildodge or @Jared B?