Rear End Gear Ratio

Discussion in 'Ask An Owner Operator' started by Gazoo, Aug 5, 2007.

What Rear Ratio

Poll closed Aug 12, 2007.
  1. 2.79

    0 vote(s)
    0.0%
  2. 2.93

    50.0%
  3. 3.58

    25.0%
  4. *

    3.73

    25.0%
  1. Gazoo

    Gazoo <strong>Resident Mental Patient</strong>

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    Hey guys, I am looking at trucks Tomorrow and Wed. What is a good rear ratio for fuel fuel mileage and overall hill climbing?

    Detroit 430hp, 10 spd.

    2.79?
    2.93?
    3.58?
    3.73?

    those are pretty much what they have in stock.
     
  2. MACK E-6

    MACK E-6 Trucker Forum STAFF Staff Member

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    It depends really on what you are going to use the truck for and where you will be driving. If you are going to pull a lot of heavy loads over mountains then you want a higher number. If you expect to be running the flatlands then a lower number would serve you better.
     
  3. Brickman

    Brickman Trucker Forum STAFF Staff Member

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    The dealer should have a computer program to input all your requirements and make recommendations from there. You'll want your RPMs around 1400 at 65 for the best MPGs.
    That'll put you at 1700/1800 at 75 mph.
     
  4. Brickman

    Brickman Trucker Forum STAFF Staff Member

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    Right on KW's home page there is a BUNCH of info on specing.
     
  5. kd5drx

    kd5drx <strong>Master of Electronic Communications</stron

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    Like other have said it depends on where you will run most of the time and what you will be pulling most of the time. The dealer can put it all into his computer and figure out where to gear it for you and you can always have the pumpkins changed later if things change its a little expensive but it can be done pretty easy. The best ratio is to have your engine run at the sweet spot RPM at the speed you will be running most of the time. If you run the east coast mainly then 65 if you run out west allot the 70 or 75 in the sweet spot. Usually the Detroit's like it around 1400-1550 or so is a good range. I personally don't like the 10 speed but if thats what they offer so be it a 13 or 15 over will give you better fuel millage over all because you can keep it in the sweet spot allot easier. A friend of mine hauls allot of M/T trailers and he has his geared real tall and when he is heavy he can't get into high gear most of the time but he hardly ever runs loaded and get around 8 mpg out of his T600 with a 500 HP Detroit.
     
  6. kelgar50

    kelgar50 Light Load Member

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    I have a 2000 XL running a 60 series 470 linked to a 13spd direct with 2.93 rears and 22.5 lo-pros.
    MPG is good around 6.8 on avg. pulling a stepdeck.When I pulled refers at 78,000 to 80,000 all the time I got 5.9-6.2 on a reg. basis.
    I would def go with a 13 direct over the 10spd for the simple fact that it is better for climbing the hills.
    As far as the pull goes it climbs fine I can hold my own just fine.
    Exmp. while running with a friend of mine with a 06' XL with a 515 series 60 with a 13 over and 3.58 rears and 22.5 lo-pros with me being 4000 lbs heavier he could stay at my side but could not get around me.
    Examp.#2
    While with a another friend with a 60 series 470/500 in a W900 with a 13 over and 3.55 rears running lo-pro 22.5 rubber at the same wieght as me(within 1000 lbs.) climbing up Tehachapi I ran off and left him without a problem.
    Also the nice thing is at 65 mph I run about 1375-1400 rpm.So it helps the mpg for sure.And while running in Ca at 60 mph im about 1300 rpm.
     
    Captredbeard Thanks this.
  7. Gazoo

    Gazoo <strong>Resident Mental Patient</strong>

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    Thanks for all the info guys.
     
  8. 25(2)+2

    25(2)+2 Trucker Forum STAFF Staff Member

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    Schneider runs 2.93 gears with that motor from used truck specs I have read, Wal-mart ran 2.79, but they would tend to haul lighter loads. I'm running 2,62 pulling mostly heavy hard pulling trailers, not a good set-up for performance, either MPG or pulling. A 13 is better for mpg, but lots of the high ratio trucks have OD transmissions even in 9 and 10 speeds. It depends on what you find. My company bought those trucks used pretty cheap and then put Rigmasters on them, those suck, too.:biggrin_2556:
     
  9. juan0311

    juan0311 Bobtail Member

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    don't lesson to the others that tell you that you need to drive at 65 for the best sweet spot, i am looking at my last 3 fuel up, 8.40, 8.22, 8.52 mpg and i can go on with my fuel up, my rear ends are 355 with a 10 speed auto shift i have a pre egr motor so that does help with the fuel mileage i also run under 60mph. people that knows more about me about fuel mileage says by slowing down 1 mile you gain 1/10 of a mile in fuel mileage gain, so if you drive 70 and slow down to 60 you will gain 1 full mile per gallon, and also if you buy a truck that is a non aero dynamic truck you will loose 1 mile to the gallon compared to a truck that is aero dynamic such as a columbia, t 600, ect. with the same specs as a non aero. i would prefer the 2.79 gears direct drive because that is a 5/10th gain in fuel mileage with the direct drive my next truck will have them gears, trying to hit 9mpg for the future my fuel surcharge is .52cpm@9mpg=4.58 per gallon is what i will be getting for my fuel, meaning i will be getting paid for putting fuel in my truck, i hope fuel keeps on rising.
     
    banjo317 and Frontman Thank this.
  10. Dryver

    Dryver Road Train Member

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    Why would anyone buy a Rigmaster?, horrible APU. Suck is too nice a term for them.
     
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