Allan Gibbs said:
What is the first number in relation to the second (or the "1")? Thanks.
It is an indication of how may revolutions the input makes in relation to the output.
For instance, 3.35 to 1 indicates that the input (engine) rotates 3.35 revolutions to the output's 1 revolution. As the gear selected "go up", the ratio usually "go down", as in the fifth gear ratio of .94 to 1; which indicates that the engine turns a little less than one revolution to the output's one - this is known as an overdrive gear as the output turns more than the input.
A low gear (high number) gives more power to the rear wheels, along with rapid acceleration, but the engine runs out of revs. That's when you shift - less "power" to the wheels, but you can go faster. On some hills, or when you need a burst of speed, you down shift (shift to a lower gear).
Added to the over-all gear ratio is the ratio of the transmission's output gearing to the rear "axle"s. This is usually known as the "final drive" gear ratio and unlike the transmission, is not usually "shift-able" (although you can disassemble the axle/transaxle and replace the gears). On some cars, the transmission and the final drive (rear axle) are two separate units. On others, like the Elise, the transmission and the final drive are combine in one unit and are referred to as a transaxle.
The engine speed maximum RPMs and the transmission ratios, final drive ratio, and tire size determine the car's maximum speed in each of it's "gears".
Tim Mullen