All vehicles have rack and pinion gears in their steering systems. These gears are capable of converting the rotation of the vehicle into linear motion. The steering wheel is what will rotate the gear within the rack, and as it turns, the rack will move to the right or left based on how you turn the wheel.
Gears do several important jobs, but most importantly, they provide the proper gear reduction in vehicles. This allows the correct output speed with the appropriate amount of torque. In order to understand the likeness of gears; imagine two 2-inch shafts where each has a 1-inch radius. The one gear has a 4-inch gear on it and the other will carry an 8-inch gear on it. Now, if you take a single pair of teeth that are meshed in between the gears, the ends of each shaft become the radiuses of each shaft. Therefore, you have a gear ratio that is determined by the distance of the gear and the point of contact.
If you take a splined output shaft, you can place two gears on it. These two gears will be able to move freely back and forth along the splines in the shaft. The smaller of the two gears is considered the second speed gear. There is a splined recess that is designed to slip over the splined stub that protrudes from the input shaft. The larger of the two gears is considered the low and the reverse gear. The larger gear is able to shift in order to mesh with the reverse idler gear.
The torque needed comes from the smaller gear so that the larger gear can read it. Gears are used to increase the shaft speed through the torque applied. Sometimes the need for torque increases, which is the reason we have gears in our vehicles. For example, the gears adjust the direction of the rotation in the differential on your car. You have one shaft that is in the center of your car where the differential will turn ninety degrees in order for the wheels to move.
Today, most of the gears used in vehicles are helical gears. Helical gears have teeth that are cut in such a way that they are angled to the face of the gear. This is so that there is a gradual engagement of the gears. Helical gears consist of bearings that support any thrust load. They are the quieter gears that are used in nearly all transmissions so that noise and stress is eliminated while driving.
Hypoid gears are also used in many vehicle differentials today. These types of gears allow the input to be lower than the radius of the ring gear. Hypoid gears will lower the driveshaft in a vehicle so that the passenger compartment side of the vehicle is not used. Therefore, the vehicle is capable of having more room for people and cargo.
Worm gears, on the other hand, are like no other gears in a vehicle. The worm gear set consists of a shallow worm (shaft) and gear. The worm has an angle that is capable of easily turning the gear, but the gear cannot turn the worm. Worm gears are used when there is a large gear reduction needed. In other words, a lot more torque is needed for power to be transmitted to the wheels. For this reason, worm gears are primarily used in high-performance cars and trucks.