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How do you find out the gear ratio?

2005 freightliner columbia. detroit 60 475-515; 10 speed transmission. truck won't climb very well and we drop gears like crazy even with a light load. could it be the gear ratio and how do we find that out?

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Here's KR's guide for calculating rear end ratio.

How to Calculate Your Rear End Ratio

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Equations to find:

MPH =(60*EngineRPM)/(TireRPM*RearRatio*XFinal)

Tire RPM =(EngineRPM*60)/(RearRatio*XFinal*RoadSpeed)

X-Final Output =(60*EngineRPM)/(RearRatio*TireRPM*RoadSpeed)

Engine RPM =(RearRatio*TireRPM*XFinalRatio*RoadSpeed)/60

Rear Ratio =(60*EngineRPM)/(TireRPM*XFinal*RoadSpeed)

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What does the #60 represent ?

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Rear end ratio is usually listed on the door tag where the Vin Number is.

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Its also stamped on the rear end housing

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On the front axle the ratio is on the side of the differential, on the rear axle the ratio is marked on the top of the diff. You can also take the numbers stamped on the input shaft of the rear diff, divide the first number by the second and that will give you the ratio. Flr marks the ratio on a tag just under the fuse panel on the pass. seat. Sit in the passenger seat, and pop off the plastic panel with a flat screwdriver. Your ratio will be there towards the bottom right of the sticker. This is only on the century, cascadia, columbia and coronado models. The fld and classic models are marked inside the glove box.

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There is usually a component info sheet under the cover in-front of the fuse panel axle ratio is in the lower right in the gray aria.

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it is real complicated. jack up the front drive axle, put a mark on the driveshaft and another on a tire and then spin the driveshaft( trans in neutral) by hand if the driveshaft spins 3.55 revolutions per 1 revolution on the tire or wheel then you have 3.55:1 ratio.

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requires only common sense no algebra needed

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Jenni and Rob Kebler will be eternally grateful.
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