The jargon patrol/Gear Ratios: How do gear ratios contribute to your ability to move as quickly as possible from one spot to another?
It's a basic three-step approach from engine to wheels. The steps of an engine in operation are: engine crankshaft to transmission input shaft, from here to transmission output shaft, and from here to the drive axles (by way of the differential). The ratios in the transmission determine how much of the turning power reaches the wheels. The lower gears have higher ratios to reduce the power output to the wheels, so that one turn of the crankshaft leads to a reduction in the number of rotations of the output shaft.
For example, in first gear, with a ratio of 3.44:1, the input shaft must turn 3.44 times for the output shaft to turn once.
As you move up the gears the ratios decrease until, usually in fourth or fifth gear, the ratios reverse with, for example, an 80 per cent turn of the input shaft resulting in a full turn of the output shaft. These are called overdrive gears (where the ratio is less than 1:1).
Another common term is 'the final drive' gear ratio, which is the number of times the crankshaft needs to turn to power the wheels for one full rotation.