September 23, 2024

Juan Valenciana

12th Grade

St. Francis Preparatory School 

Drivetrains are the key to how your vehicle moves, transferring the power from the engine to the transmission and making the wheels turn so that the car can drive. 

In a car, the engine burns fuel to create energy, similar to how when you pedal a bike, you generate power with your legs. The transmission is the first major component within the drivetrain. Based on the driver’s input, such as pressing the gas pedal or shifting gear, the transmission adjusts how much power the engine should be putting out by changing gear ratios and modulating the amount of torque (circulatory force) put through to the wheels. 

Low-Speed Torque: When a car starts moving from a stop or needs to go up a hill, it needs a lot of torque. Lower gears in the transmission (like first or second gear) multiply the engine's torque, making the car more powerful at lower speeds. Once the car begins moving on a flat road, it doesn't require as much torque. Higher gears (like fourth or fifth gear) don’t multiply torque as much which in turn allows the car to reach higher speeds. 

Engines need gears to be able to have low-speed torque, yet still be able to shift those gears for higher-end top speed without going over their max rpm limit. Without a transmission, the engine would be slow to start with just high gears, or fast to start, but have a very limited top speed. 

Transmission Control Module (TCM) is the ‘brain’ of the automatic transmission system. It uses sensors for the vehicle’s speed, engine load, and other factors to automatically determine when to shift gears. Furthermore, automatic transmissions use hydraulic pressure to engage and disengage gears. In this system, a torque converter replaces the clutch by allowing the transmission to decouple or disengage from the engine and transfer power from the engine to the transmission. 

The differential is important because it enables the wheels to turn at different rates, particularly during turns. Without a differential, the wheels would all be forced to rotate at the same time which would lead to worn-out tires and overall poor handling of the vehicle. 

Most rear-wheel drive cars have an open differential, which allows the rear wheels to spin independently of each other. Most cars utilize open differentials. A limited-slip differential (LSD) allows for a smaller difference in wheel speed but reduces excessive slip when one wheel loses traction. For example, if one wheel starts spinning rapidly due to ice or mud, LSD transfers some of the torque to the wheel with better traction improving overall stability.

Driveshafts connect to the transmission and the differential via universal joints. The driveshaft transfers the power of the transmission to the differential. This power being transferred is from the front part to the rear end of the vehicle where the differential is mostly located. 

The last link in the drivetrain after the differential is the axles, the strongest weight-bearing component of the vehicle. The axles, along with the driveshaft, are directly responsible for turning the tires. 

The drivetrain system connects the engine’s power with the wheels to allow the car to drive. By balancing differential wheel spins during turns, drivetrains also play a role in handling and stability. Maintaining the drivetrain system is necessary for vehicle performance and longevity.