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question about gearing

Discussion in 'Trucks [ Eighteen Wheelers ]' started by dgc, Dec 19, 2012.

  1. Dec 19, 2012 #1
    dgc

    dgc Light Load Member

    92
    46
    Dec 2, 2012
    miami, fl
    0
    i spoke to Mr Haney about reprogramming my ecm and about bringing my gear ratio from a 355 to 336. I currently run 68 mph at 1500 rpm. He told me what speed i would be going at 1500 rpm with the 336 but i dont remember and dont want to call and bother the man with a question.

    Can anyone help.. i have an 18 sp with 355 and 24.5 lp
     
    dgc, Dec 19, 2012
    dgc, Dec 19, 2012
    #1
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  3. Dec 19, 2012 #2
    e500gvr

    e500gvr Light Load Member

    125
    32
    Aug 21, 2006
    Bloomington,MN
    0
    Engine Speed (RPM) ​
    ​
    ​
    ​
    ​
    = MPH x Rev x Ra x Rt​
    60​
    Where:​
    Rev = Tire revolutions per mileRa = Rear axle ratioRt = Transmission ratio​
    CalculationsTable 1Table 2Table 3​
    Other UsefulFormulas​
    Glossory of TermsHorsepowerStartabilityIndustry StandardStartabilityRequirementsVehicle CruiseSpeedRecommendedEngine CruiseSpeedWhat Is?​
    13
     
    e500gvr, Dec 19, 2012
    e500gvr, Dec 19, 2012
    #2
  4. Dec 19, 2012 #3
    JackZ

    JackZ Bobtail Member

    24
    6
    Jul 7, 2011
    Winston-Salem, NC
    0
    If all you're changing is the rear axle ratio and everything else is the same, you can figure out the new road speed by applying the percent change in the ratio. Meaning that you are changing the axle ratio by 5.4% (3.55-3.36=.19 then .19/3.55=.054 or 5.4% decrease). So with the same engine RPM the road speed would increase by 5.4% or 3.7 MPH for a new speed of 71.7 MPH.
     
    JackZ, Dec 19, 2012
    JackZ, Dec 19, 2012
    #3
    dgc Thanks this.
  5. Dec 19, 2012 #4
    bubbanbrenda

    bubbanbrenda Road Train Member

    1,388
    649
    Feb 27, 2011
    Middletown,Oh.
    0
    http://big-rig-road-speed-calculator.blogspot.com/2011/03/semi-truck-road-speed-calculator.html

    Saved it to my favorites, very handy.

     
    bubbanbrenda, Dec 19, 2012
    bubbanbrenda, Dec 19, 2012
    #4
    dgc Thanks this.
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