3:36 vs 3:91

Discussion in 'Ask An Owner Operator' started by Randhawa.56, Jan 5, 2022.

  1. Randhawa.56

    Randhawa.56 Bobtail Member

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    Hello truckers, I got a cascadia 2016
    Dd16 500hp 13 spd 22.5 tires And 3:91 gear ratio. The mpg im getting is 4.9 on 69-72mph
    I wanna know if i will chage gear ratio to 3:36 how much difference it will make.
    Thank you
     
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  3. Magoo1968

    Magoo1968 Heavy Load Member

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    It should improve dramatically 3.91 is a heavy haul gear. Dd16 is a low rpm motor
     
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  4. Pamela1990

    Pamela1990 Road Train Member

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    How much do you weigh when loaded?
    Mountainous terrain, or flat lands?
     
  5. Randhawa.56

    Randhawa.56 Bobtail Member

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    40000lbs on flats
     
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  6. Pamela1990

    Pamela1990 Road Train Member

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    Definitely use some taller gears then.
     
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  7. ProfessionalNoticer

    ProfessionalNoticer Road Train Member

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    You may be able to switch to taller tires or wheels instead of changing gears depending on how far gone you're current tires are.
     
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  8. AModelCat

    AModelCat Road Train Member

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    Cost vs reward.

    How long will it take to break even on the cost of re-gearing?
     
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  9. dirthaller

    dirthaller Heavy Load Member

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    Interesting that you chose 3.36 to compare to because 3.36 is exactly 1/2 gear above 3.91. You’ll be running the exact same speed at the exact same rpm only now your transmission will be in 12th gear instead of 13th. So basically you’ll be adding another overdrive gear. If you want to burn clutches up, you can go to 2.85 gears and be exactly a whole gear above 3.91 (basically same speed/rpm in 11th gear vs 13th)
     
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  10. abyliks

    abyliks Road Train Member

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    If you are on low pro rubber I would try and go to an 11r or 12r first.

    taller gears are great until you go to take off loaded, even my 3.55s are a smidge to tall, 3.91 are about a perfect highway gears if you are running 11r24.5
     
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  11. Brettj3876

    Brettj3876 Road Train Member

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    Talk about overkill for flat land and legal weights Lol
     
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