What does a flywheel do?

Your truck, SUV, or that performance car’s torque and power are determined by the powertrain it has. The powertrain consists of the engine and drivetrain. And the drivetrain consists of front and rear differentials, axles, transfer case, driveshaft, wheels, and transmission. These components are responsible for providing the torque and power your performance car, SUV, or truck needs to move forward and backward.

One of the essential components of the powertrain we fail to mention above is the flywheel. If it fails, it will cause several adverse effects on other powertrain components.

Now, you may be wondering what does a flywheel do, and what the heck is it. This article will unveil three functions of a flywheel and bad flywheel symptoms.

What Is A Flywheel And How Does It Work?

what does a flywheel do in a small engine

You have likely heard the words powertrain and drivetrain. It is also likely you know that these components provide power and torque to move your vehicle. But I doubt you know all the components that make up a powertrain. And flywheel may be unfamiliar to you, despite its essential role in the movement of your vehicle.

The flywheel is a heavy metal disc placed in between the engine and the transmission. It is installed with mounting bolts at the back of the crankshaft. It is designed in a coin form with gear teeth around its circumference. The function of these gear teeth is to hook and revolve with the starter motor as you start the vehicle.

Your clutch is mounted on the back of the flywheel. This is why many mechanics debate on the subject of ” is flywheel a part of the clutch system or not”. Amidst this, it is worth noting that a flywheel is attached to an engine to increase power and torque.

However, you need to understand that automatic vehicles do not have flywheels, instead, they have flexplates. So, if you have an automatic vehicle, you don’t have to worry about the signs of a bad flywheel. They are found in manual transmissions, however, there are manual transmissions that don’t rely on them. That said, how does a flywheel work?

Now that you know what is a flywheel in a car, whether your vehicle has it or not, and where to find it, let’s discuss how it works. As explained earlier, it is found in between the engine and transmission and increases the engine torque and power by storing rational energy.

One of its primary functions is to smoothen the fluctuating forces created during the combustion process. It starts carrying out these functions once you start your engine.

As explained not long ago, it works together with the clutch system. Once an engine is running, it creates mechanical forces that need to work in conjunction with the transmission, the powertrain achieves this with the help of a flywheel. It keeps transferring these mechanical forces from the engine to the transmission. And this continues as long as the flywheel is working optimally. If you’re asking ‘what does a flywheel do in a small car?’ A straight-to-the-point answer is, that a flywheel does the same thing on all manual transmissions.

what does a flywheel key do


Q: What are the signs of a bad flywheel?

One of the things you wouldn’t want to give up without signs on your car is the flywheel. It may mean you are going to park your vehicle in a garage until you replace it. Luckily, some signs will pop up before the flywheel goes out. They’re as follows;

  • Rattling noise when you depress or release the clutch pedal.
  • Gear goes into neutral or slips out when shifting gears.
  • Burning smell from the clutch.
  • Regularly vibration when driving
  • Your car produces strange noise when turning the starter motor

Q: Does Flywheel always spin?

We explained earlier that the flywheel keeps transferring power from the engine to the transmission once you start a car. So, you might think the flywheel spins all the time. That’s not true. The flywheel does not spin when in neutral.  This is because the input shaft that connects to the clutch plate; then to the pressure plate which connects to the flywheel is designed to spin freely when the vehicle is in neutral.

Q: Can I drive with a bad flywheel?

Apparently, you can drive with a bad flywheel. It all lies in how severe the damage is. In some cases, a flywheel will keep you stranded in the middle of nowhere.

Before deciding to keep driving with a bad flywheel, you should note that when a flywheel goes out, it can cause damage to other powertrain components in that area because the flywheel serves as a balancer between the engine and the transmission as the crankshaft rotates. If it stops acting as a balancer, there will be vibrations as you drive. A rough idling will hinder the engine from producing peak performance.

Q: Why is flywheel so expensive?

There are two types of flywheels; fixed and dual flywheels. Fixed flywheels are considerably affordable to all car owners. On the flip side, dual flywheels are more expensive than their variants because of the material used in production. However, a standard-style flywheel lasts much longer and hardly requires replacement.

Q: What happens if the flywheel breaks?

Since the main function of the flywheel is to transmit power from the engine to your tranny, if it suddenly breaks or fails, it will cause unexpected and severe damage.

It will also cause vibrations, rattling noise, gear slippage or hard shifting gear, or strange noise when turning the starter motor. In a worst-case scenario, it will cause your engine to underperform and lose torque and power altogether.

Q: How much does it cause to resurface a flywheel?

If there’s discoloration or glazing on the surface of the flywheel; it is a sign of wear, which can disrupt the smooth meeting of the flywheel with the clutch. If this happens, you’ll need to resurface the flywheel. A resurface job should be between $20 to $50. This, however, does not include your mechanic’s service fee.

Q: Does the flywheel need to be replaced with a clutch?

If you notice gear slippage or any other symptoms of a bad clutch, and upon inspection, you find out you have a worn clutch disc, you don’t necessarily need to replace the flywheel. However, it is recommended to resurface the flywheel in a high-mileage vehicle whenever you remove the clutch.

Q: How long does it take to machine a flywheel?

There are two methods of resurfacing a flywheel. The methods include grinding and cutting. Whichever method you chose to adopt, resurfacing a flywheel will take 3-5 minutes.

The purpose of resurfacing the flywheel is to remove the hard surface while leaving it with a homogeneous and smooth surface.

Q: How many times can you resurface a flywheel?

There’s no specified number of times to resurface a flywheel. However, I recommend resurfacing it once or twice, and nothing more than that.

In any case, Machine operators will be able to tell whether you need to resurface a flywheel or it’s long gone and needs a replacement by merely looking at it. This is their job, they do it often.

Final Word

At this juncture, you won’t be asking what is a flywheel, what it does, and the symptoms to watch out for when it goes bad.

Not only does this article provide a sufficient answer to the question ‘what does a flywheel do’ it also unveils the consequences of driving with a bad flywheel. Suppose you notice any of the symptoms above, consult your mechanic for professional inspection and fixes.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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