good ratio for mpg

Discussion in 'Trucks [ Eighteen Wheelers ]' started by hellpatrol, Dec 29, 2016.

  1. vangtransport

    vangtransport Heavy Load Member

    863
    2,837
    Apr 14, 2009
    0
    With a Cummins ISX @ 67mph, 13 spd trans & 3:42's would be in the sweet spot with 295/75 R22.5's.

    Cummins has a online tool: https://cumminsengines.com/powerspec
     
    hellpatrol Thanks this.
  2. russtrucker

    russtrucker Road Train Member

    1,767
    337
    Mar 27, 2012
    Central PA
    0
    My volmins (daycab 2016 volvo with isx15). 2.64 rear gear. 10 sp ultrajunk with .80 top gear, makes it run 65 mph at 1200 rpm. Gross 30k-60k lbs. Gets 6.5-7.4 mpg driving around pennsylvania. I would get the same mpg when I drive 08 t800 with 10 speed standard and isx400 1750 lb ft. 65 mph at 1400 rpm, .74 top gear, 2.53 rear gear.
     
    KB3MMX Thanks this.
  3. hellpatrol

    hellpatrol Light Load Member

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    172
    Apr 22, 2013
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    I was running last night and discovered that at 10 pounds of boost my rpm's were almost always around 1,300 in any of the higher gears. I also ran the other night keeping my boost around 10#'s max and I gained 0.5 mpg. So if I wanted to keep the engine right around that 1300 mark to keep the boost down and run a gear lower than max(17th in this case) then it seems that I should be running these gears too.
     
  4. JORTRUCK

    JORTRUCK Light Load Member

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    Mar 9, 2017
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    I can giveyou this
    Ratio 336
    HP 505
    DD15
    DT12 AUTO
    You think for this spaces okay to pull reefer 53 trailer. Good for mpg and do you think the truck go up hills smoothly ?
     
  5. KB3MMX

    KB3MMX Road Train Member

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    2,589
    Dec 29, 2014
    Orrstown, PA
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    Too tall for me.

    I'd never go that high anymore, the downspeed drivetrains have made me a believer. The pulling is still similar but with better fuel mileage in general.

    I've also been told the 2.64 axle won't pull and they've been proven wrong.

    Against a 3.25 truck I run with, it pulls the same but I consistently get much better MPG on same runs similar gross #. It's been great to be able to do this and see a direct comparison.
     
    uncleal13 Thanks this.
  6. russtrucker

    russtrucker Road Train Member

    1,767
    337
    Mar 27, 2012
    Central PA
    0
    Correction. 10 speed manual i drove on an 08 t800 with 2.64 rear end is actually a direct drive tranny on 10th gear.
     
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