Gears might be “old” technology, but they are still considered the most rugged type of mechanical drives. They transmit power with efficiencies of up to 98% and have long operational lives. That’s why gears and not belts or chains are used in automotive transmissions and most heavy-duty machine drives. Gears are also versatile and can serve to increase output torque by providing gear reduction and also be used to adjust the direction of shaft rotation, such as on the driveshaft to the rear wheels of cars and trucks.
Here's a look at some basic types of gears.