time2roll wrote:
The top gears for fuel economy are not a big concern to me. But to lose 4 of your gears all at the top seems poorly balanced. I would rather be in the middle 6 ratios for normal conditions. For economy I would have 2 more at the top, and for an unexpected steep condition have two more at the bottom. A lower 4.10/4.56 would present this flexibility. I would worry more about getting started on a 15+ percent incline more than a bit of economy.
I don't see how you would say that you would lose 4 gears at the top? If you look at the pictures posted by the OP of the 3.73 ratio in both the 6 and 10 speeds, you will see that the 6 speed 6th gear is close to 10 speeds 9th gear. The 6 speeds 5th gear is close to the 10 speeds 8th gear. The 6 speeds 4th gear is the 10 speeds 6th gear and so on.
I know with towing close to 10k in my old 2011 F150 3.5L Ecoboost with 3.73 gears, it would easily hold 5th towing that much which means that the 10 speed would easily hold 8th gear since those two gears are similar. In fact, if you factor in the 50 lb-ft of added peak torque in the new gen 2 Ecoboost, the 6 speeds 5th gear is putting 1,348 lb-ft to the wheels and the 10 speeds 8th gear is putting more at 1,489 lb-ft to the wheels.
And if you compare a 6 speed 4.10 to a 10 speed 3.55 on how much lb-ft each are putting to the wheels factoring the added peak torque of the new EB, you will see that a 10 speed 3.55 will easily go tow to tow(pun intend) with the 6 speed 4.10.
420 lb-ft Gen 1 EB 6 speed w/4.10
1st: 7,182 lb-ft
2nd: 4,028 lb-ft
3rd: 2,617 lb-ft
4th: 1,961 lb-ft
5th: 1,482 lb-ft
6th: 1,189 lb-ft
470 lb-ft Gen 2 EB w/3.55
1st: 7,826 lb-ft
2nd: 4,973 lb-ft
3rd: 3,572 lb-ft
4th: 2,938 lb-ft
5th: 2,538 lb-ft
6th: 2,120 lb-ft
7th: 1,669 lb-ft
8th: 1,419 lb-ft
9th: 1,133 lb-ft
10th: 1,053 lb-ft
There is also the factor that high rpm turbocharged engines benefit more from taller gears due to being able to utilize there low end torque and broader power band. Basically you are staying in lower gears with its torque multiplication longer. It is mainly N/A engines that benefit more from shorter gearing since their power is higher in the rpm.
time2roll wrote:
I understand those tractor/trailers don't always use the lowest gear to get moving. Or do they?
Not when unloaded. You can start in 3rd of 4th when unloaded. Heck, you can even bypass gears going from 3rd to 6th just like I heard this Ford 10 speed does.
