What Is a Powertrain?
Hannah DeWitt
· 4 min read
When
buying a car
, it can be difficult to know what the upsides and downfalls of a car are if you don’t know certain terminology
. But don’t worry, we’re here to help. With some help from WhichCar
, we’re here to tell you just what, exactly, a powertrain is.
What’s a powertrain?
Powertrains are what makes cars move—everything that creates and directs power from the engine (or motor in electric cars) to the wheels.
An engine might generate a car’s power, but the rest of the powertrain is what gets that power to the wheels and moves the car.
For combustion cars, the powertrain is made up of five parts: the engine, the transmission, the driveshaft, the differentials, and the axles. Each of these parts play a role in getting energy to the wheels, allowing them to roll.
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Parts of a powertrain
- Engine
The engine is in charge of generating power. It uses combustion, the burning of gasoline, to turn the liquid into air. This air creates pressure that moves pistons within their cylinders, which then rotates a crankshaft, transferring the energy.
- Transmission
The transmission consists of the gearbox and the clutch. These elements turn the power created by the engine into rotational for the gears in the gearbox to determine how much force is being applied and at what speed, in order to best transfer the energy to the wheels. When the car is going slower and using a lower gear, the force applied is greater but is applied at a lower speed. When the car is moving faster, less force is supplied but at a higher speed.
Newer cars with automatic transmissions don’t need a clutch to shift gears, but manual-transmission cars require the driver to use a clutch to shift gears and change speeds.
- Driveshaft
The driveshaft is responsible for sending the rotational power, or twist, from the engine and transmission down to the wheels. It consists of a long shaft running the length of the car, right down the middle. It carries the energy by rotating, which is why it’s also known as a propeller, or “prop”, shaft.
The only car type where a driveshaft is not necessary is in cars with front-wheel drive and front engines. Since the power has such a short distance to travel, the long reach of a driveshaft isn’t needed.
- Differentials
Differentials control the amount of power given to each wheel. If wheels each received the same amount of power in any situation, they would always spin at the same speed, which isn’t conducive to turning.
The outer wheel would need to speed up while the inner one wouldn’t, so one wheel would just be spinning mostly in place to compensate for the other’s speed. The differential lets wheels spin at different speeds, splitting the power between each as needed, which helps them grip the road better.
- Axles
Finally, axles are what actually allow a wheel to turn. An axle is a shaft on which wheels (or gears) rest and rotate. It’s what makes wheels actually turn.
Put them together, and you have the powertrain. However, this isn’t quite the same as the drivetrain, which is another common term for some of these parts.
Are powertrains and drivetrains different?
Drivetrains are different from powertrains, but only slightly. “Drivetrain” refers to every part in the powertrain aside from the engine (and sometimes the transmission, depending on who you ask).
This means that it refers to the transmissions, driveshaft, differentials, and axles—everything that works to transfer the engine’s power to the wheels.
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