Math at work · auto shop, worked out

The Gear Box

The math in a shop, one step at a time: gear ratios, road speed from engine rpm, tire sizes and speedometer error, displacement, compression ratio, horsepower and torque, fuel economy and trip cost, coolant and 2-stroke oil mixes, and the invoice. Plain unit changes are on the Measuring Tape, ratios on their own on the Ratio Table.

For learning and shop practice. Follow the manufacturer’s specs and the service manual: fluid types, capacities, mix ratios, torque values and tire sizes come from them, not from this page. The numbers here are worked examples.

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The work

Say it out loud

    Ratios, mixtures and money are kept exact, as fractions, until the last step; where a number is rounded, the step says so.