Thoughts on 3.08 diff ratio

Discussion in 'Ask An Owner Operator' started by Truckie6674, Mar 2, 2021.

  1. Truckie6674

    Truckie6674 Bobtail Member

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    Thinking about changing my diff ratio to 3.08s
    How would the 3.08s fare in hills behind a 12.7 w 470hp and a 18sp
    Usual run is from Tx to Colorado in the mountains.
    Thoughts?
     
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  3. Spyro2112

    Spyro2112 Medium Load Member

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    Fuel mileage, I'd go up a little more
     
  4. dirthaller

    dirthaller Heavy Load Member

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    Just put it in 17th gear and pretend it has 3.55s.
    Use 18th as a bonus gear and get used to starting in low when loaded on a hill.
    That’s the way I think anyway as my truck has 2.93s and I run 17th pretending that it has 3.42’s.
    The late great Cowpie1 (former poster) had 2.64s with his 12.7 jimmy and ran in 16th to pretend 3.55s.
     
  5. Speed_Drums

    Speed_Drums Medium Load Member

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    Don't mean to derail the thread but Cowpie1 died?
     
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  6. magoo68

    magoo68 Road Train Member

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    18 speed you can use darn near any ratio . The only difference will be shifter location. Engine doesn’t know what rear ratio or transmission gear it’s in. Keep your rpm on a pull where you have it now whether that’s 16/17/18 it don’t matter
     
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  7. AModelCat

    AModelCat Road Train Member

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    Sadly yes.
     
  8. dirthaller

    dirthaller Heavy Load Member

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    In 17th gear...........
    3.36=3.90
    3.25=3.70
    3.08=3.55
    2.93=3.42
    2.85=3.36
    2.64=3.08
     
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  9. Speed_Drums

    Speed_Drums Medium Load Member

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    That's sad. Was it a long time ago?
     
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  10. rollin coal

    rollin coal Road Train Member

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    When did cowpie pass away?
     
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  11. AModelCat

    AModelCat Road Train Member

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    I read about it a week or 2 ago. I think it was quite recent, few months maybe?
     
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