2021 Cummins 1075 lbft peak torque at 1356 rpm

Grit dog wrote:
Or, assuming your calculated rpm at certain speeds and certain gears, regardless of vehicle, the closer the gear splits (more available gear ratios within a certain speed range), the less of a rpm jump or drop and the greater the ability to match desired speed, and rpms (up/tq) balance.
I’d argue if your numbers are right, dropping or gaining 500-600 rpms with a single gear shift is not ideal and more available ratios will only serve to improve performance by staying ever closer to the perfect sweet spot at more given road speeds.
Does the 10 speed Ford really have 500 rpm drops between gears especially in the upper gears? If so, I’d say it doesn’t have ideal ratios for towing and maybe wasted a gear or 2 too many on upper high speed “cruising” gears.
The 6 speed is good but not ideal, talking Cummins or any other diesel pickup. The more the merrier.
There’s a reason heavy haulers have 18 speeds, besides the big engines havin a much smaller useable rpm range, it’s also to keep the truck putting out the most available power to the ground over the greatest speed range.
Or simply put, more gears the better, within reason.

7 th gear is 1:1 in the 10r140 and 6th is 1.277:1. So a downshift at 2114 rpm in 7th brings the engine speed to 2700 in 6th. 5th is 1.519 :1 so dropping from 6th at 2270 rpm would bring the engine up 2700 in 5th.