Why might you have a transmission with a set of low gears and a high 2.73 axle ratio over a car with a transmission that has 2 or 3 overdrive gears a set of high gears with an axle setup of 4.10 instead?
There are usually more then one way to get the car moving, like you say. The gearing in a transmission is usually more expensive to change to fit various car light truck models, so they change the read end gears. A tranny in a light passenger car could maybe handle at 'shorter' gear, like a 2.73, but if you stick that same tranny in a heavier pick-up truck, it needs at taller gear, like a 3.27, to get the heavier truck rolling. The taller the rear end gear, the faster the acceleration, but the lower the top speed. The manufacture has to balance the different vehicle models it makes using the fewest number of different transmission types, so he can buy more of one type of tranny get it cheaper.
