Gears

Discussion in 'Ask An Owner Operator' started by Thotphobia, Jun 12, 2021.

  1. Thotphobia

    Thotphobia Bobtail Member

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    Hey guys, does anyone have a semi with 13 speed c15 with a gear ratio of 3.90? Are they any good? We’re looking at one and was curious as to how they perform. Thanks !
     
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  3. Brettj3876

    Brettj3876 Road Train Member

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    Probably be around 1400-1600 rpm at 65 depending on tire size. Not the best for a speed demon but good all around gear set
     
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  4. Dino soar

    Dino soar Road Train Member

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    I don't have a C15 but my truck has 390 rears and with a .73 overdrive I think at 70 I'm doing about sixteen hundred RPMs with 11R 22.5 tires. 11R 24 5 Tires with slow that down a little.

    But those 390 rears will make you pull like a mean beeeyyyotch.

    Google Road Ranger Road speed calculator that will give you a good idea of road speed and RPMs.
     
  5. Rubber duck kw

    Rubber duck kw Road Train Member

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    What are you going to pull with the truck? Just regular 80k pound gross that's way too high a gear.
     
  6. Brettj3876

    Brettj3876 Road Train Member

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    No not at all. Unless you run 75+ everywhere. Depending on tire size he'll be around 1500 at 65 with Lp24.5 and or 70 at 1500 with tall 24 5

    That's on the upper end of the sweet spot
     
  7. mtoo

    mtoo Road Train Member

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    In my humble opinion that set up is perfect with tall 24.5 rubber. Only thing better would be coupled to an 18 speed. But I like a work truck, not that concerned about the last .05 MPG increase
     
  8. mtoo

    mtoo Road Train Member

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    One other thing you might look out for. If you you have tall 24.5 rubber and a high 5th wheel mount, you could have problems with over all height, depending on the trailer you pull and/or the load.
     
  9. Cattleman84

    Cattleman84 Road Train Member

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    Have run many such setups in Agricultural work... Great off road setup. Its not going to get great fuel mileage... But if your looking at CAT engines you probably already know that.
     
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  10. AModelCat

    AModelCat Road Train Member

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    I like OPs handle. Thots scare me too.
     
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  11. abyliks

    abyliks Road Train Member

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    Rto or rtlo trans and what size rubber? And what are you hauling and where?

    Should be a perfect all around gear with an rtlo and tall 24.5s
     
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