Mines a 2014 Limited edition.
LOVE the truck, but then again, I've owned a 2003 Chevrolet Duramax/Allison dually, a 2006 Dodge Ram 3500 Cummins w/ 6 speed manual and a 2011 Ford F-350 dually PowerStroke 6.7L automatic previous to this one.
The 2011 Ford got better fuel mileage than my current Ram when hauling around the same truck camper. Power was NOT a problem, stopping at Dave Smith Motors was the problem. Just kicking tires looking, and I drove away in my new Ram instead of the Ford. :B
As far as my Ram I've got the 385 Cummins/Aisin in mine. Wonderful combination, but fuel mileage could be better. I average about 11.5 loaded, which is lower than my 2011 Ford got. Not by much mind you, but it is somewhat less.
That said, you may want to consider the normal speed you travel towing or hauling your RV as a deciding factor on which rear axle ratio you wish to have.
Mine has the 3:73 ratio, same as all my previous vehicles.
I find the Aisin in this one can go gear hunting at times, especially should I be driving in the say 61 to 63 MPH speed range. It'll shift back and forth from sixth to fifth gear until I get tired of it and lock sixth gear out.
Increase my speed to 66 MPH and it stays in sixth all the time.
Problem with mine is the Aisin doesn't shift to sixth gear until 58 MPH in tow/haul, so I think it's just not far enough into sixth, so to speak, to stay there at my cruising speeds of 61-63 MPH. A 4:10 axle ratio would solve this, as it shifts into sixth sooner, I believe at around the 54 MPH mark. Other posters have remarked their MPG with the 4:10's are similar to mine with the 3:73's.
Best of luck.
