Spur gears are the most common kind of gears. They possess straight teeth, and are mounted on parallel shafts. 
Sometimes, many spur gears are utilized at once to create large gear reductions.
Spur gears are found in many products that you can see around HowStuffWorks, like the electric screwdriver, dancing monster, oscillating sprinkler, windup noisy alarms, washing machine and clothes dryer. But you won’t find many in your car.
This is since the spur gear could be really loud. Each time a equipment tooth engages a tooth on the various other gear, the teeth Super Power Lock collide, which impact makes a noise. In addition, it increases the stress on the gear teeth.
To reduce the noise and stress in the gears, most of the gears in your vehicle are helical.