The '11 Dodge/Cummins has the aluminum case G56 6 speed manual tranny (around 280-300 lbs with a clutch).
gears are
1st..5.94
2nd..3.28
3rd..1.98
4th..1.30
5th..1.00
6th..0.94 OD
reverse..5.42
The Cummins has the zero throttle launch . No slipping the clutch just let the clutch out and the Cummins throttles up on any slope and you don't even touch the go pedal to get it rolling.
My '03 5.9 Dodge Cummins HO has the cast iron NV5600 6 speed manual (about 400 lbs with a clutch) 3.73 gears with about the same tranny gear splits. When empty I launch in 2nd...shift to 4th...and then 5 or 6 depending on highway speed limit.
I've had the truck since new and find the Cummins/6 speed manual/Jacobs exhaust brake is a towing dream. Exhaust brake works in all 6 gear and even reverse.
I would advise you to drive it for a while. There a big heavy tranny and shift nothing like a 3-4 speed manual tranny in a car/1/2 ton truck so there not for everyone. It does take a lot of foot/arm and brain coordination to make seamless up and down shifting without knocking the U joints out.