While you may have heard of a drivetrain, you may not be familiar with how it works. The term is often used interchangeably to also refer to powertrain or driveline equipment. A drivetrain includes the transmission, driveshaft, axles, and wheels. With this in mind, the drivetrain works in tandem with the engine to rotate the wheels. As movement is a vehicle’s primary function, the drivetrain system is an essential component to such structures.
Like most systems, drivetrains also have components that are integral to their functionality. Drivetrain systems, in particular, depend on the transmission to perform optimally. The foremost purpose of the transmission is to keep the engine turning in time with the wheels, regardless of what gear the vehicle is in. As the drivetrain backs the transmission, the drivetrain generates power from the vehicle’s engine, directing it through the transmission to drive the wheels to control the amount of torque.
Beyond the transmission, there are other various components that allow the system to operate. This collection of components that transfer power from the transmission to the wheels to drive a vehicle forward include the driveshaft, CV-joints, U-joints, differential, and axle shafts.
The driveshaft is a steel or aluminum cylinder that connects the U-joint near the rear axle to the U-joint at the back of most transmissions, allowing the transmission to provide torque to the wheels.
Next, the CV-joint (constant-velocity joint) has a malleable design which enables it to bend in any direction, giving the axle the ability to move with the vehicle while still turning the drive wheels. Moreover, CV-joints are located on front-wheel drive vehicles where the driving shaft joins the front axle to the front driving wheels.
The U-joint (universal joint) is a flexible point on the driveshaft that enables the shaft to pivot and rotate as the wheel goes over bumps or dips on a road.
The differential consists of a housing that contains the axle gears and the differential itself. It is usually located in the middle of the axle and distributes power to each drive wheel. More than that, the differential allows the wheels to move at varying speeds. The differential is positioned on the drive wheel’s axle, that of which is the front axle for front-wheel drive, the rear axle for rear-wheel drive, and both axles for all-wheel drive configurations.
The differential contains multiple axle shafts, which deliver power from the differential to the rear drive wheels.
How the Drivetrain Works
For rear-wheel drive (RWD) and front-wheel drive (FWD) vehicles, the drivetrain works very differently. In RWD vehicles, the drivetrain uses the transmission to control the power that travels from the engine to the wheels. Then, the driveshaft connected to the transmission rotates rapidly, allowing for the transfer of power to the rear differential. Finally, the rear differential distributes power to the rear axles and rear wheels. In the case of FWD vehicles, these mechanisms are confined to the front. Without a driveshaft to carry engine power to the back of the car, the work is done by the transaxle. The latter is a housing that combines the functions of the transmission, axle, and differential into one assembly.
While knowing how the drivetrain works is important, it is even more critical to understand how to detect if you have a failing drivetrain. You can identify if your drivetrain is malfunctioning if there are unusual noises, fluid leaks, vibrations, problems shifting, or of course, an illuminated “check engine” light.
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