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How Does An Engine Actually Move A Car? Wheels In An Engine

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If you're curious about how all the wheels in an engine truly work, then read on to learn about the flywheel, clutch, transmission, drive shaft, and more.

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  • How Does An Engine Actually Move A Car? Wheels In An Engine

The engine is the most vital piece of gear that a car has. It works in tandem with every moving or power-reliant aspect of the vehicle, and no component functions well without it. In previous articles, we've explained how many parts of a car work to keep you on the road, such as:

Yet none of these can power your car on their own. So, what moving parts actually make up the total of an engine, how do they work, and what do they accomplish to make your car the robust, convenient machine it is? Let's take a closer look at how all the wheels in an engine work:

The Flywheel

When you start your car, engine cylinders are forced into motion. This creates energy, which is used to rotate the crankshaft. To translate that power to the rest of the vehicle, this crankshaft is connected to a flywheel.

By and large, the flywheel helps to smooth the motion of the engine by maintaining rotational inertia. As such, while your engine runs, the flywheel spins and evens out the discrepancies between the motion of the cylinders.

In theory, you could attach this directly to a few gears and use that to turn some wheels – but then you would only be capable of going or stopping when you turned the engine on and off, respectively. Moreover, you could only drive within a limited speed range.

Considering the amount of power required to activate the engine through a starter motor, you would quickly run your battery down in stop-start traffic. As such, to keep the engine running and allow you to drive smoothly at different speeds, you need to transmit that power through the transmission system. The first part of that system is the clutch.

The Clutch

On the other side of a flywheel is the clutch. This connects the rotational movement of the flywheel – with all its power – to the transmission system and then eventually onto the wheels. This ensures you don't have to start and stop the engine each time you want to change gears (that would also be dangerous if not impossible at speed). Instead, the clutch system lets you engage and disengage the transmission from the flywheel.

When you press the clutch pedal down, a cable is pulled, which yanks the clutch plate away from the flywheel. This essentially removes the power transmission from the engine. This is similar to turning the engine on and off, but without having to actually meddle with the engine's power.

The Transmission System

The transmission system is a relatively complicated set of gears, which multiply or divide the power coming out from the engine. Drivers control this power supply by using the gearbox to change gears.

The change is noticeable to drivers; when in first gear, you can't go very fast, but more power is going to the wheels to keep them from becoming stationary. When you're in neutral, the transmission system isn't connected, so you can take your foot off the clutch (which technically engages the clutch), but your car doesn't stall, because there's no load on the engine.

When you try to engage the clutch in first gear, you need to match the required force by putting more power into the engine (through the accelerator pedal). Now, because the transmission system turns directly with the wheels, if the wheels aren't moving, then they'll stop your engine from moving when the clutch is engaged. This is why your car stalls if you didn't get the biting point right.

However, if your car is already moving, it takes far less power to get it moving slightly more. That makes it relatively easy to change gears when you're going at the general speed.

The Drive Shaft

On the other side of the transmission is the drive shaft. This shaft brandishes a hinged connection on either side. When driving on the road, your car is subjected to a host of different forces as it accounts for bumps and unevenness in the road. The drive shaft needs to be rigid in order to effectively transmit the torque from the engine to the wheels, but if it's a single rod, then it can't account for any flexing.

That's where the hinges come in. They allow the front and end of the drive shaft to move up and down, as well as change angle, within certain parameters while still rotating.

The actual construction of a drive shaft can vary dramatically between cars. That's because it's surprisingly difficult to transmit power from the engine, across a distance, and to the wheels.


The end of the drive shaft is attached to a component known as a differential. This is like a big cog, set at a right angle to the drive shaft.

As such, the rotation of the drive shaft is turned into rotation along the axis of the axles, and then the wheels. The differential is also tasked with accounting for differences in wheel speed between the left and right sides, like when driving through corners.

All together, these are the most important wheels in your engine. If you're concerned about any aspect of your car's drive train, don't hesitate to get in touch with your local Autofusion Centre.