Allison Custom Gear Ratios

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    Jason DJason D

    YES, it is possible to run an Allison with my system that has custom gear ratios.  The only limitation is what gear ratios are currently available for the Allison.  The 2500-2550 series medium duty transmissions had the “wide ratio” gear sets from the factory, all others had the “close ratio” set.

    5 speeds are the same with the exception of the 6th gear ratio.   These gear sets can be interchanged into the 1000 to 2400 series transmissions with the right supporting parts and set up.

      1st 2nd 3rd 4th 5th 6th Reverse
    “wide ratio” 3.5 1.9 1.44 1 0.74 0.64 5.09
    “close ratio” 3.1 1.81 1.41 1 0.71 0.61 4.49 offers billet carriers with at least one custom ratio set.


    On Xcaliber website search for “P3 Performance Kits” for custom gear ratios.

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