will a truck with 2.64 gears pull?

Discussion in 'Ask An Owner Operator' started by Evilcapitalist, Nov 3, 2008.

  1. Eskimo6804

    Eskimo6804 Heavy Load Member

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    Northeast Alabama
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    The 2.64 and 2.79 ratois are matched to direct drive(1:1 final ratio) transmissions. The 2.64 with direct drive is equivalent to a 3.55 with overdrive, and a 2.79 is equivalent to a 3.70 with overdrive. Some of the big companies spec these direct drive transmissions because they supposedly get a little better fuel mileage than an overdrive. This is due to having less moving parts in the tranny and thus less mechanical drag. That is the theory anyhow...I don't really know how much of a difference it would make, but any little bit helps I guess.
     
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  3. rjones56

    rjones56 Heavy Load Member

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    Depends on transmission and tire size.Most overdrives geared for lower numbered rears.The shorter the tire the better the truck pulls,taller tires will get better fuel mileage.My truck has a DDEC 4,430\470 hp, 13spd w\.73 overdrive on low-pro 22.5 tires.I run the east coast,fuel mileage is 5.5 or less.Wish I had 11r24.5 tiers but would probably wear out the trans shifting. As is the truck does a good overall job.Got 6.75 mpg from lower AL. to Philly last week but I only had 860# in the box.
     
  4. 7mouths2feed

    7mouths2feed "Family Man"

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    There sounds like you have a problem if you are getting only 5.5 with that combo. Could be either mechanical or personal but something is definately amiss there. 24 talls would drop your RPM's by about 75 rpm (assuming 3.36 gears) which wouldn't be a big difference in milage for you and would not make a big difference in shifting.. Look elsewhere for the problem.


    Evil I PM'd you the info you will need to figure RPM's for a given set-up.
     
  5. OwnerNotOperator

    OwnerNotOperator Light Load Member

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    El Paso, TX
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    Well I have a 435hp 3406E CAT with a super 10 trans and a 3.55 rear end in a '99 Freightshaker Classic XL and is currently averaging 6.72 MPG. Worst mileage so far was 6.2 MPG with 44,000lbs in the van from El Paso TX to Claycomo MO...(oh and its 1.3 million miles and counting)

    just my 2 cents
     
  6. Cowpie1

    Cowpie1 Road Train Member

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    Kellogg, IA
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    And there is an operator, Randall Corlee, that pulls fuel in Oklahoma, with a Pete 389, running a C-15 Cat, tied to an 18 spd (running in direct 16th gear), hooked up to 2.64 rears, running 65-70 mph, that gets 7.5 - 8.2 avg mpg.
     
  7. kinglenn

    kinglenn Bobtail Member

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    How's a setup like that climb? I been thinking of getting an 18 speed in my truck . Cascadia dd13 2.64 ratio. 10-speed direct. I'm averaging 6.8 to 7.4 mpg now , but would love to get to 8plus a gallon the way things are now.
     
  8. kinglenn

    kinglenn Bobtail Member

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    Oh and I'm pulling a tanker with sugar
     
  9. Cdemars316

    Cdemars316 Light Load Member

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    I put 2.74's in my Pete, went from 3.55's I have a 15 sp low reduction which has a tallish od (.79) compared to most have a .72 when I am in direct it is geared the same as it was in overdrive with the 3.55's or a little better actually at 70 I am right around 1500 rpm's in direct, the old 3.55's and overdrive at 70 I was about 1625 for rpm's. It pulls hills way better in direct then it ever did in overdrive. The only reason 2.74's work with this transmission is because of my low reduction gear to start off in when loaded. Hopefully by the end of the year I will have an 18spd in the truck, its on order right now. with an 18sp in first overdrive (17th gear is .86) I will be at around 1300-1350 at 70 which imho is perfect for fuel mileage. Right now with my current setup I am right around 6.5 mpg those are all miles loaded and empty, I still struggle and always will with vans in the wind and am around 4-5 in those situations. But even the most aero truck with proper gearing and setup struggle in North Dakota winds in the winter. I personally love the new gearing, it pulls the highway better, took awhile to get used to but once I have if you are all highway I say lower is better, my truck is now a highway princess and I don't do offroad crap with it anymore so it works for me
     
  10. DRTDEVL

    DRTDEVL Road Train Member

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    Drive ratio is drive ratio, it doesn't matter what the actual combination of gears are used to get there. if a 1:1 and a 2.64 is used vs a and 0.74 and 3.55, you end up with a difference of only 0.03, or 30 rpm for every 1,000. Negligible, and delivering the same torque multiplication through to the hubs (well 1800 * 2.64 vs 1800 * 2.637, so 4,752 lb-ft vs 4,728.6 lb-ft to the hubs). They will pull exactly the same, just a different means of achieving the same effect. Then add in the lower parasitic drain in a direct drive vs. overdrive, and now the trucks with 2.64 and direct drive have a fleet average of exactly 8.5 mpg (I just pulled the cumulative mpg YTD reading off the spreadsheet for all 2021-2023 models in the fleet and looked at the mean) pulling heavy reefers.

    Those extra 2 mpg are huge when multiplied by 50 trucks. We're talking the difference between 17,647 gallons/year and 23,077 per truck. Those 5400 gallons of fuel savings can be used for much better things, like more driver comforts, higher paychecks, and better benefits. That's 270,000 gallons/year at 50 trucks, or a savings of over $1.2 million... or around $25,000 for the independent.

    I'm sure you all could use an additional $25,000 in profit every year, right? That's why the manufacturers have come up with this formula.
     
  11. RunningAces

    RunningAces Road Train Member

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    I pull a flatbed with a used Melton truck, isx15, 425hp, 10 speed automated with 2.64s and I can tell you for certain I don't pull mountains for ####. I don't care though let the traffic pile up behind me and I'll laugh all the way to the top at 25mph.
     
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