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. rank

    rank Road Train Member

    9,823
    110,622
    Feb 11, 2010
    50 miles north of Rochester, NY
    0
    That’s more or less where my truck runs and I have a 13 with low pro 22.5 and 4.33 rears. BTW in most 13 speeds 11th is direct, not 12th.
     
    Oxbow Thanks this.
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  3. wore out

    wore out Numbered Classic

    12,989
    163,473
    Jun 5, 2013
    CHASIN THE DEVIL'S HERD
    0
    I think we discovered in another thread the original 13 speed went tits up. So it was replaced with a RTO15613 which ends in .87 or an easy way to say it a half hole short from what everyone today is used to.
     
    Oxbow and rank Thank this.
  4. Largecar359

    Largecar359 Road Train Member

    1,074
    1,311
    Aug 13, 2011
    New Jersey
    0
    Yeah that's where he's getting burned on the top end. .73 final drive gives it the legs it needs.
     
    rank, Oxbow and wore out Thank this.
  5. Lalito.1234

    Lalito.1234 Light Load Member

    113
    24
    Dec 1, 2015
    irwin,il
    0

    I thought over drive was stronger than direct???????????
     
  6. Brettj3876

    Brettj3876 Road Train Member

    9,813
    45,202
    Nov 18, 2014
    Stuck in Limbo
    0
    1700 sounds about right. Plug these numbers in the calculator.

    40 in tire
    3.55
    .87
    1700 rpm

    Transmission Ratio RPM Calculator | Spicer Parts
     
  7. ulenie

    ulenie Medium Load Member

    319
    192
    May 24, 2018
    Houston, TX
    0
    Is 13 speed with 4.33 a heavy haul spec? Currently looking at a 12.7 DD with that rear end for OTR work, max 80K gross(usually bt 75 to 80K). Looking to cruise at 65mph. Drive mostly in flat lands
     
    rank Thanks this.
  8. Final Drive

    Final Drive Road Train Member

    1,573
    2,478
    Jan 21, 2015
    0
    I feel left out, why no 370 ?:(
     
  9. DougA

    DougA Road Train Member

    1,429
    8,877
    Dec 16, 2013
    Retired,In my shop in Md.
    0
    I know this is an old thread,but yes,they used to make a 13 speed direct,haven't seen one in a long time. Had one in my 1969 IH COF4070A. NTC 335 Cummins,13 speed direct,4.11s,tall 10:00-22 rubber. When you came out of the low side,you split under the gears,instead of over. 13 direct was high gear.
    Was a very good running truck,in its day.
     
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  10. rank

    rank Road Train Member

    9,823
    110,622
    Feb 11, 2010
    50 miles north of Rochester, NY
    0
    HH not by a darn site. Truck has a M11 and it needs a 4.33:1 rear
     
    DougA and Oxbow Thank this.
  11. Driver Eight

    Driver Eight Light Load Member

    241
    131
    Oct 26, 2012
    0
    I haven't actually located that? I do happen to have lousy online search skills, so its probably a me thing. I did see something google referenced, but I could not find on the site, something as called "T680 Online Truck Configurator"
     
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