Spur gears are the most typical kind of gears. They possess straight teeth, and are mounted on parallel shafts. Occasionally, many spur gears are used at once to create large gear reductions.
Spur gears are used in many products that you can see all over HowStuffWorks, like the electric powered screwdriver, dance monster, oscillating sprinkler, windup noisy alarms, washing machine and clothes dryer. Nevertheless, you won't discover many in your car.
This is since the spur gear can be really loud. Each time a gear tooth engages a tooth on the additional gear, the teeth collide, which Sprocket impact makes a noise. It also increases the stress on the gear teeth.
To lessen the noise and stress in the gears, 
the majority of the gears in your car are helical.