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ACZL's avatar
ACZL
Explorer
Dec 09, 2020

Curiosity caught the Cheshire cat

Went past a Ford dealer couple weeks ago and noticed he had 2 SD dallies on the lot. Stopped by the following week to take a gander at them. 1 was a 450 Lariat and the other a 350 XLT. 79 and 70K respectively. Anyways, didn't spend a whole lotta time there, but on the 350 (very well equipped), it was a '21, 4.10 gears and had the 10 speed tranny. So it got me to thinking and perhaps a little drooling too, but what is the RPM difference between a 4.10 6 speed and 4.10 10 speed at 60-70 mph? On my '17 350 w/ the 4.10 6 spd, I'm at 2100 at 70 mph.

29 Replies

  • Boomerweps wrote:
    IDman wrote:
    I'm curious too. What is a dallie?

    I suspect an auto spell corrected DUALIE.
    My auto correct has also displayed words that don't exist. And it's dually.
  • MFL wrote:
    Good info Shiner, tire size guess, no problem!

    Jerry


    I just went off average tire sizes for the past F350/450's. It appears I was very close after looking it up. The new F450 has 225/70R19.5 which is 31.9 inch in diameter.
  • Too funny - four out of six responses tell us what he meant, but does not speak to his comment.

    From personal driving experience, without the engineering data. We went from a four speed tranny and 3:73RE to a six speed tranny and a 4:10 RE. Did not notice a significant difference in actual 'feel', and the power and mileage seemed very similar. I still got 15-17 mpg empty, and 12-14 hauling. Climbing hills hauling was the greatest 'feel different' as the 4s x 3:73 was less power, while the 6s x 4:10 pulls really well.

    But the 6s x 4:10 was ten years newer, so advances in technology besides the gear ratio makes a difference too. If I had a choice, I'd go with the 6s x 4:10 again without a second thought.

    I know, not the 6s vs 10s tranny, but still a change in gearing and a result from it.
  • BurbMan wrote:
    IDman wrote:
    I'm curious too. What is a dallie?


    I think he meant Duallie


    I knew what he meant . . . ;)
  • IDman wrote:
    I'm curious too. What is a dallie?

    I suspect an auto spell corrected DUALIE.
  • IDman wrote:
    I'm curious too. What is a dallie?


    I think he meant Duallie
  • Good info Shiner, tire size guess, no problem!

    Jerry
  • 10th gear in the 10R140 is .632:1 and 6th gear in the 6R140 is .674:1. That is a 126 rpm difference at 70 with 32 inch tires putting the 10R140 at 1,905 rpm and the 6R140 at 2031 rpm in their final gear. I am not sure what the size the F350/450 tires are so that is just guess.