Gear Fundamentals

     Gears are used to transmit turning effort from one shaft to another. Gear ratio is thenumber of revolutions a drive gear must turn before the driven gear completes onerevolution. Transmission gear ratios vary from one manufacturer to another. However,approximately gear ratio is 3，1 for first gear, 2，1 for second gear, 1，1 for third，orhigh gear，and 3，1 for reverse gear.

    First gear has a high gear ratio. A small gear drives a larger gear. This reduces outputspeed but increases output torque. The car accelerates easily, even with low engine speedand low power conditions.

    In high gear, the transmission frequently has a 1，1 ratio. The transmission outputshaft spins at the same speed as the engine crankshaft. There is no torque multiplication,4ibut the vehicle travels faster at relatively low engine speeds. Very little torque is needed topropel a vehicle at a constant speed on level ground.