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.

I very seldom use the 18 speeds in our big trucks but it is nice to have them. Empty I will jump across 4 gears at times. Loaded I usually use every second gear until I'm cruising. If the engine is happy at 1200 rpm I keep it in that gear, if there is a bit of a wind and I need to pick the rpm up a little I'll drop 1/2 gear. If I hit a hill and I know I'm going to be dropping multiply gears I'll drop 2 gears to bring the engine rpm up to 2000 or 2100. So the gears are nice to have.

When you compare the power curves of the Cummins to the Powerstroke you can see that running at 2100 rpm with the Cummins is no big deal .... you're only giving up at the most 20 horses and if the engine slows the power is only dropping off slightly. So, it's time to downshift if the hill is slowing the truck more but it's a good place to be if the engine and hill are at an equilibrium or if the engine is gaining a bit on the hill.
The Powerstroke, on the other hand, even with a 10 speed is giving up about 65 HP by running at 2100rpm with your foot to the floor in 7th vs 2682 in 6th. So it downshifts and when the load is steady the jump in HP will cause the truck to accelerate ... so it does. And now your revving at 2800 rpm and on the verge of an upshift as soon as the hill relaxes even just a bit... and the cycle continues.

So the Powerstroke needs 10 gears to use its power band and it will beat the Cummins up the hill, but, even with its 10 gears it doesn't have the beautiful pulling characteristics of an engine with a 36% torque rise. If Ford could push the torque up to 1200 lbft @ 2000 rpm and leave the power where it is then we would have the cat by the tail.