<P> Belts can have teeth in them also and be coupled to gear - like pulleys . Special gears called sprockets can be coupled together with chains, as on bicycles and some motorcycles . Again, exact accounting of teeth and revolutions can be applied with these machines . </P> <P> For example, a belt with teeth, called the timing belt, is used in some internal combustion engines to synchronize the movement of the camshaft with that of the crankshaft, so that the valves open and close at the top of each cylinder at exactly the right time relative to the movement of each piston . A chain, called a timing chain, is used on some automobiles for this purpose, while in others, the camshaft and crankshaft are coupled directly together through meshed gears . Regardless of which form of drive is employed, the crankshaft - to - camshaft gear ratio is always 2: 1 on four - stroke engines, which means that for every two revolutions of the crankshaft the camshaft will rotate once . </P> <P> Automobile drivetrains generally have two or more major areas where gearing is used . Gearing is employed in the transmission, which contains a number of different sets of gears that can be changed to allow a wide range of vehicle speeds, and also in the differential, which contains the final drive to provide further speed reduction at the wheels . In addition, the differential contains further gearing that splits torque equally between the two wheels while permitting them to have different speeds when travelling in a curved path . The transmission and final drive might be separate and connected by a driveshaft, or they might be combined into one unit called a transaxle . The gear ratios in transmission and final drive are important because different gear ratios will change the characteristics of a vehicle's performance . </P> <P> A 2004 Chevrolet Corvette C5 Z06 with a six - speed manual transmission has the following gear ratios in the transmission: </P>

Where do you find a simple gear train