13 spd Transmission and RPM's. Best cruising gear?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Turbrospeed, Nov 23, 2021.

  1. Turbrospeed

    Turbrospeed Bobtail Member

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    Hey guys just wanting to get your opinion.

    Can i cruise in 12th gear for long periods of time?

    Reason i ask is becuase in 13 gear my rpms are only at 1280 at 70 and sometimes with alot of wind i get bad fuel mileage so i have to put 12 n go 60ish so my rpms can be around 1400
     
    Pamela1990 Thanks this.
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  3. xsetra

    xsetra Road Train Member

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  4. blairandgretchen

    blairandgretchen Road Train Member

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    Won’t hurt anything. I re geared from 3:70 to 3:55, and often set the cruise at 62 at 1525 rpm when it’s windy, or heavy.
     
    jamespmack, Pamela1990 and Turbrospeed Thank this.
  5. BoxCarKidd

    BoxCarKidd Road Train Member

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    Actually a little easier on the trans. Back box is direct instead of running power through counter shafts.
     
  6. Turbrospeed

    Turbrospeed Bobtail Member

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    If you dont mind me asking, how much did you pay to re-gear?

    And do you just change the gears in one or both diffs?
     
    blairandgretchen Thanks this.
  7. xsetra

    xsetra Road Train Member

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    Differentials gears have to be the same. Change both.
     
  8. Turbrospeed

    Turbrospeed Bobtail Member

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    Very rare that i use the cruise, ive gotten use to my foot on the pedal, cause i stare at my mpgs like a religion
     
    blairandgretchen Thanks this.
  9. Turbrospeed

    Turbrospeed Bobtail Member

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    Thanks for your replys guys... I usually go around 70 and currently getting 8.2 mpg average, but if i go 60-65 in 12 gear i can get 9+
     
    blairandgretchen Thanks this.
  10. wore out

    wore out Numbered Classic

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    Not quite. On the RTLO transmission back box is an under drive unit. When the button is in direct the back box is turning which is using power flow and making heat. Eaton actually advises against running with the button in direct for long periods though I have never personally seen it anything it hurt. When the button is in overdrive the power flow runs straight through the trans. Which is less rotating mass etc.
     
    BoxCarKidd, stwik, Roger McG and 5 others Thank this.
  11. Pamela1990

    Pamela1990 Road Train Member

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    I cruise in 16th or 17th often in my 18 speed. Never be concerned about cruising in top gear, unless it is the right conditions to do so.
     
    Last edited: Nov 24, 2021
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