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Differential ratio

Discussion in 'Engine & Performance' started by Ypogeo, Apr 19, 2019.

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  1. Ypogeo

    Ypogeo Junior Member

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    I drive a 1991 Dodge E 250 with Cummings 3 speed automatic trans and 3:07 differentials. I live where the access road has an adverage grade of 25%. The engin doesn’t hold the truck back when I go down the hill. At 5 mph the engin at idle pushes me. I think the best way to fix this problem would be lower differential gearing. I hear that they made 4:11 differentials for the truck.
     
  2. Ypogeo

    Ypogeo Junior Member

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    Forgot to mention that the truck is in 4wd low range when I drive down. What do you think
     
  3. crash68

    crash68 Senior Member

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    Gearing isn't going to help as much as an exhaust brake will. Diesels don't have a butterfly to create vacuum like a gas engine, here why diesel don't naturally engine brake. Semi trucks use Jake brakes, but that utilizes exhaust valve to build pressure in the combustion chamber. With the Cummins exhaust brake it restricts the exhaust for the same effect, they are commonly added to trucks that tow heavy travel trailers.
    https://www.dieselpowerproducts.com/c-105-1989-93-59l-dodge-cummins-exhaust-brakes.aspx
     
  4. crazzywolfie

    crazzywolfie Senior Member

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    i think that would probably be a bad idea to change gears. you will lower your top speed by at least 25mph and these things seem like they have a hard time doing much over the speed limit as it is stock. i know my buddies 4x4 diesel would just do the speed limit on the highway with 3.07 gears and no overdrive on 37's. i would hate to see it with 4.10. it would probably max out at 60mph in overdrive. max gear ratio i would consider for a diesel is 3.55 unless you get a transmission with more gears.
     

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