2021 Cummins 1075 lbft peak torque at 1356 rpm

4x4ord wrote:
Your 10 speed sounds like a good set up. I’ll take you on with the 6 speed Aisin if I can have 3.31 gears. I’ll bet we will find the extra gears aren’t going to buy you much. How about we pull an 18000 lb toy hauler cruising down the highway a 63 mph and say you get 9 mpg with your rig. Then we’ll go 70 mph empty and say you get 18 mpg with yours. Then we’ll climb a 7% grade towing and see how they compare. Then we can compare how they would do heading into a 20 mph wind towing at 55.

Looks like my excel screenshots disappear, Google image hosting doesn't work.

I took the estimated torque curve you posted, fitted it with a polynomial equation which I then used to calculate the Tq and hp at every speed / gear combination:



You'll notice a "Tq %" input highlighted with a red box. With this, we can play with different throttle setting, and see if we can get into the magical [550 - 1000 lb-ft] + [1500 - 2000 rpm] range.

For example, at 60% throttle, I've highlighted (in darker blue) where torque remains above 550:



I'll let you calculate out the scenarios to see what grades can be pulled at the corresponding hp values.