The effective ratio of every single gear is altered it the final drive ratio is altered with, thereby affecting performance and economy. It is basically the gear ratio of the gear train. The gear ratio of a gear train is also known as its drive ratio and is the ratio of the angular velocity of the gear inputted to the output gear. The gear ratio can easily be calculated directly from the number of teeth on the gears of the gear train. Using the principle of virtual work to show that its torque ratio (which is the ratio of gear train’s output torque to its input torque, is equal to the gear ratio, or speed ratio, of the gear train), a gear train can be analyzed. The drive ratio and mechanical ratio are so defined that they yield a number which forms an ideal linkage.
Automobile drive terrains generally have two or more major areas where gearing is used. To achieve a great range of vehicle speeds, and also in the differential a gearing system is employed in the transmission which contains a number of different sets of gears which can be changed for that purpose and contains the final drive to provide further speed reduction at the wheels. Further, the differential contains further gearing which splits torque equally between the two wheels while allowing them to have different speeds while moving in a curved path. A transaxle is the combination of the transmission and final drive into a single unit or they might be separate and connected by a driveshaft. The gear ratios in transmission and final drive are important because they will change the traits of the vehicle's performance.