ASVAB Auto Information: Transmissions
The automotive transmission system is a crucial component of a vehicle, acting as a bridge between the engine and the wheels. Its primary purpose is to transfer power from the engine to the wheels while allowing the vehicle to operate at different speeds and under various conditions. The transmission system accomplishes this by changing gears, which alters the ratio of engine rotations to wheel rotations.
At the heart of the transmission system is the gearbox. This complex assembly contains a series of gears of different sizes that can be engaged or disengaged to change the gear ratio. The gear ratio determines how much power is transferred from the engine to the wheels and at what speed. Lower gears provide more power but lower speed, while higher gears offer less power but higher speed.
The clutch is another essential part of the transmission system, particularly in manual transmissions. It allows the driver to disconnect the engine from the transmission temporarily. This is necessary when changing gears or when the vehicle is stationary but the engine is running. In automatic transmissions, a torque converter performs a similar function to the clutch, but it operates automatically without driver input.
The gear shift, whether it's a stick in a manual transmission or a lever in an automatic, is what allows the driver (or the car's computer in an automatic) to select different gears. In a manual transmission, moving the gear shift engages different gears in the gearbox. In an automatic transmission, the gear shift tells the car's computer which range of gears to use.
Torque is a crucial concept in understanding transmission systems. It refers to the rotational force produced by the engine and transferred through the transmission. The transmission system helps manage this torque, providing more when needed (like when accelerating from a stop) and less when high speed is more important than power.
The driveshaft is the long tube that connects the transmission to the differential at the driven wheels (usually the rear wheels in rear-wheel drive vehicles). It transfers the rotational force from the transmission to the wheels, allowing the car to move.
Other important parts of the transmission system include the differential, which allows the driven wheels to rotate at different speeds (necessary when turning), and the axles, which connect the differential to the wheels themselves.
In recent years, continuously variable transmissions (CVTs) have become more common. Instead of fixed gears, CVTs use a belt or chain running between two pulleys that can change diameter, allowing for a continuous range of gear ratios.
Understanding the transmission system is key to appreciating how a vehicle converts the engine's power into motion, allowing us to drive at various speeds and under different conditions.