If you’ve ever driven a manual shift car, then you’re probably familiar with the clutch. It’s the third pedal that you have to press in order to change gears.
However, you might not know exactly what the clutch does, especially if you’ve only driven cars with automatic transmissions.
What is a clutch and why do you need one? Because your engine is always spinning, there has to be a way for the wheels to disengage so they can stop moving. This is where the clutch comes into play. It can disengage the wheels without killing the engine.
What is a Clutch?
A clutch is a mechanical device used in the transmission system of a vehicle. It engages and disengages the transmission system from the engine. It is fixed between the engine and the transmission.
The power produced inside the engine cylinder ultimately aims to turn the wheels so the vehicle can move on the road. The reciprocating motion of the piston rotates a crankshaft by rotating the flywheel through the connecting rod.
The circular movement of the crankshaft is now to be transferred to the rear wheels. It is transmitted through the clutch, gearbox, universal points propeller shaft or driveshaft, differential, and axles extending to the wheels.
With the help of all these parts, the use of engine power for the driving wheel is called power transmission. The utilization of engine power to the driving wheels through all these parts is called power transmission.
The power transmission system is normally the same on all passenger cars and trucks. But its design and arrangement may vary according to the method of drive and type of transmission units.
What Does the Clutch Do?
Everyone knows that a car has an engine to power it, but not everyone is familiar with a clutch or how it works.
This mechanism both engages and disengages your power transmission from the driving shaft to the driven shaft. It connects rotating shafts, and there can be two or more of these under your hood.
If you drive a manual transmission, the clutch is connected to both the shaft coming from the engine and the shafts that turn the wheels. While the motor is going to spin constantly, you don’t want the wheels continually spinning.
One of the rotating shafts is going to be connected to the engine or power unit, this will be the driving member, while the other rotating shaft, or driven member, provides output for work.
For example, a drill has a shaft that’s driven by a motor and one that’s driven by a drill chuck.
How Stuff Works explains that the clutch connects the shafts so they can be engaged (spin at the same speed), slipping (spinning at different speeds), or disengaged (spinning at different speeds).
Typically, you’ll find that these motions are rotary; although, linear clutches are possible.
Key Components of a Car Clutch System
The clutch system consists of several interconnected parts that work together to enable gear shifts. Here are the main components you should be familiar with:
#1. Clutch Disc.
The clutch disc is a circular, friction-coated plate positioned between the flywheel and the pressure plate.
When the clutch pedal is released, the clutch disc is pressed tightly against the flywheel by the pressure plate, allowing the transfer of power from the engine to the transmission.
Over time, the friction material on the disc wears down, causing the clutch to lose its ability to grip the flywheel properly. This leads to common clutch issues like slipping.
#2. Pressure Plate.
The pressure plate is a spring-loaded metal plate that exerts pressure on the clutch disc, pressing it against the flywheel. This is crucial for ensuring that the engine’s power is fully transferred to the transmission.
When the clutch pedal is pressed, the pressure plate moves away from the clutch disc, disengaging the power flow. A worn-out pressure plate can result in a slipping clutch or difficulty shifting gears.
#3. Flywheel.
The flywheel is a heavy, circular metal plate attached to the engine’s crankshaft. It helps balance engine rotation and stores rotational energy. The clutch disc presses against the flywheel to transfer engine power to the transmission.
A damaged or warped flywheel can cause clutch vibration or shudder, leading to inconsistent performance. In some cases, the flywheel may need resurfacing or replacement during a clutch repair.
#4. Release Bearing.
The release bearing, also known as the throw-out bearing, allows smooth disengagement of the clutch when the pedal is pressed. It reduces friction between the pressure plate and the release mechanism, preventing wear on these components.
A faulty release bearing can cause noise (such as squealing or grinding) when the clutch pedal is pressed and can make gear changes difficult.
#5. Clutch Pedal and Linkage.
The clutch pedal is what you press to engage and disengage the clutch. It’s connected to the clutch system through either a mechanical or hydraulic linkage.
Mechanical linkages use cables or rods, while hydraulic linkages rely on fluid pressure. Issues with the clutch pedal or linkage, such as air in the hydraulic system or a stretched cable, can result in a spongy or stiff clutch pedal feel, making it harder to change gears.
Frictional forces are what clutches rely on to operate. Frictional clutches connect one moving member to another one that is moving at a different speed, or not at all, to get it moving at the same speed so that there is no slippage. Various materials are used to create this friction. They include:
- Compound organic resin
- Copper wire
- Ceramic
- Composite paper
You’ll mostly see ceramic materials used in racing or heavy-duty hauling situations, though this material can increase wear and tear on the flywheel and pressure plate. With wet clutches, you find the use of composite paper.
Because these types of clutches tend to use an oil bath or flow-through cooling method, they have less wear than ceramic material.
Multiple plate clutches have more than one driving member, making them ideal for racing cars such as Formula 1, Indy 500, and club racing as well. In drag racing vehicles, a lot of abuse goes to the clutch, which is why they often have this type of clutch.
It can also be found in motorcycles and diesel engines with mechanical transmissions. Additionally, you might find one in a car with an electronically controlled all-wheel-drive system and in some transfer cases too.
A cone clutch has a conical shape, and its taper means that it approaches or recedes more slowly than a disc-type clutch. What this translates to is that speeds of the shift hub and gear wheel are synchronized to give you smoother shifting when you change gears.
It’s most likely that you’ll find a centrifugal clutch in a vehicle such as a moped or machinery like chainsaws, where the speed of the engine defines the state of the clutch.
When the rpms of the engine rise above or fall below a certain level, it will either engage or disengage the clutch using centrifugal force.
A wet clutch system differs from a dry clutch in that it is immersed in a cooling fluid that lubricates it to keep it clean and extend its life. It’s important to note however, that this type of clutch will lose energy because they tend to be slippery.
Stacking multiple clutch discs can help to compensate for this slippage. A dry clutch, on the other hand, uses friction, as it isn’t bathed in liquid.
What Are the Different Types of Clutches?
#1. Friction Clutch.
This is the most common type, using friction between the clutch plate and flywheel to transmit power. It allows smooth engagement and disengagement in vehicles. Common in manual cars and easy to operate with a clutch pedal.
#2. Single Plate Clutch.
Used in most cars, it has one friction plate between the flywheel and pressure plate. It’s simple, reliable, and ideal for vehicles requiring smooth gear changes with less torque transfer compared to multi-plate clutches.
#3. Multi Plate Clutch.
This type uses multiple friction plates to transfer more torque in a compact size. It’s used in motorcycles, racing cars, and heavy-duty vehicles. The more plates, the more grip and power transfer it can handle.
#4. Cone Clutch.
Instead of flat plates, this clutch uses a cone-shaped surface to engage power. It’s more efficient in torque transmission due to increased contact area and is found in old vehicles, low-speed machinery, or race cars.
#5. Hydraulic Clutch.
This clutch uses hydraulic fluid pressure to operate instead of a mechanical cable. It provides smoother and more effortless engagement, especially useful in modern cars and heavy-duty vehicles where pedal effort needs to be reduced.
#6. Centrifugal Clutch.
Operates automatically using centrifugal force as engine speed increases. No need for a clutch pedal. Commonly found in mopeds, scooters, and go-karts, it engages only when the engine reaches a certain speed.
#7. Electromagnetic Clutch.
Engaged by magnetic force when an electric current is applied. It allows remote or automated clutch operation, often used in air conditioning units, robotics, and some advanced automatic transmission systems.
#8. Dog Clutch.
This clutch uses interlocking teeth or dogs to connect shafts directly—no friction involved. It’s used where fast, positive engagement is required, like in racing gearboxes or industrial machinery.
#9. Overrunning (Freewheel) Clutch.
Allows the driven shaft to continue turning even when the driving shaft slows or stops. It works like a bicycle freewheel and is used in automatic transmissions and generators to prevent reverse motion.
What is the function of a Clutch in a Car?
The main functions of a car clutch are:
#1. Transmits Engine Power.
When engaged, the clutch connects the engine to the transmission, allowing power from the engine to be transmitted to the wheels to propel the vehicle forward. The clutch plates join and rotate at matched speeds to transfer rotational force down the drivetrain.
#2. Enables Gear Changes.
The clutch allows the vehicle’s engine to be disengaged from the transmission when the pedal is depressed. This breaks the connection between the engine and gears, enabling smooth gear changes without grinding or clashing noises.
#3. Allows Smooth Stops/Starts.
Depressing the clutch pedal separates the engine from the drivetrain, allowing the vehicle to come to smooth and controlled stops even with the gear still engaged.
This prevents the engine from stalling at low speeds yet keeps the transmission ready to accelerate again after the clutch pedal is released.
#4. Cushions Driveline from Torque Spikes.
The clutch also cushioned the drivetrain by dampening out sudden power surges from the engine. It allows torque to be transmitted smoothly to the wheels as the engine RPM builds, preventing harsh engagements.
#5. Enables Progressive Acceleration.
As the clutch begins to grab, a small amount of slippage occurs between the plates. This brief transition progressively increases the transmission to engine speed, aligning wheel rotation for jerk-free acceleration before full lockup.
What Are The Signs Of A Worn Clutch?
Several symptoms will pop up to notify the driver of a car clutch problem. Let’s look at the detailed list of symptoms of a worn clutch.
#1. Soft clutch pedal.
The clutch pedal requires a certain degree of force on your foot to depress it, regardless of the manual transmission model you own.
If the clutch pedal becomes incredibly soft when depressed, it indicates an issue with the clutch system. This issue can arise from low clutch fluid, up or down clutch kit failure, or a problem with the pressure plate.
Whenever the clutch pedal becomes soft than usual, you may need to diagnose the clutch assembly to figure out the cause of the problem.
#2. Hard gear shifting.
A well-functioning clutch and transmission will smoothly shift into higher and lower gears. The primary function of a clutch is to release the rational force that is transmitted from the engine to the transmission.
So you can shift to different gear ranges. If the clutch fails to perform this function, you will experience hard gear shifting.
This happens to all transmissions when the clutch goes bad. So, if your gear has become extremely difficult to shift to different gear ranges lately, you need to inspect the clutch.
#3. Stiff clutch pedal.
A stiff clutch pedal indicates a problem with the pressure plate. It can also mean issues with the clutch hydraulic system, like a defective clutch master cylinder. Hence, it is advisable to diagnose your vehicle before jumping to conclusions.
Noise when depressing the clutch pedal: If you hear a strange noise when depressing the clutch pedal or changing gears, it is likely a sign of a bad throw-out bearing, drive plate, or pressure plate.
The throw-out bearing is responsible for pushing the pressure plate to engage and disengage the clutch. Like every other clutch component, this bearing can fail and cause issues. It is usually replaced with a clutch.
Whenever your car starts emitting strange noise when depressing the clutch pedal or changing gears, contact your mechanic or dealership to track down the culprit and fix it ASAP.
#4. Slipping clutch.
If you experience clutch slipping when accelerating the car, diagnose the clutch system. A bad or failing clutch typically slips, especially when carrying a heavy load or climbing hills.
In such situations, there’s a likelihood that some drivers will keep depressing the accelerator pedal to gain traction, this will only cause the engine speed to increase, but the vehicle won’t move as fast as it should.
Clutch slippage causes overheating to its components and leads to accelerated component wear and damage.
In a worst-case scenario, a damaged clutch can prevent the vehicle from moving forward or backward. This, however, won’t happen suddenly. Before it gets to this state, it’ll display some signs to notify the driver of a problem in the system.
#5. Higher clutch pedal.
Usually, when the clutch pedal starts wearing out, the pedal will come up more than its standard height. On older vehicles that use clutch cables and rods, it will require a mechanic to adjust it whenever it goes high.
In contrast, new cars use a hydraulic clutch system. The hydraulic system automatically makes this adjustment. Therefore, you don’t have to contact your mechanic to perform any adjustment tasks.
Unfortunately, if the hydraulic system wears out to the extent the hydraulic system can’t adjust it anymore (which happens earlier than the manual adjustment), the clutch will require replacement.
#6. Clutch pedal goes to the floor.
Amidst other symptoms, the clutch pedal can stay on the floor as a sign of a defective clutch. This is usually caused by a bad throw-out bearing, clutch pressure plates, or hydraulic systems.
Whenever this comes upon a vehicle, the first diagnosis should be on the hydraulic system before heading to the clutch.
Having discussed the symptoms and causes of clutch failures, let’s look at the frequently asked questions that you might be wondering about.
Maintenance Tips
- Avoid riding the clutch (keeping foot on pedal partially pressed).
- Ensure timely replacement of worn clutch disc and release bearing.
- Maintain proper clutch free play (if adjustable).
- Regularly check hydraulic fluid levels (for hydraulic clutches).
Lifespan of a Car Clutch
The lifespan of a car clutch can vary significantly depending on several factors, including driving habits, maintenance, and the type of vehicle.
On average, a well-maintained clutch in a passenger car can last anywhere from 80,000 to 160,000 kilometers. However, some clutches may last even longer with careful use and proper maintenance.
Here are some factors that can influence the lifespan of a car clutch:
- Driving Habits: Aggressive driving, such as excessive revving, hard launches, and frequent rapid gear changes, can accelerate clutch wear and reduce its lifespan. Gentle and smooth driving practices can help extend the clutch’s life.
- Maintenance: Regular maintenance of the clutch and the overall transmission system can contribute to a longer clutch life. This includes checking and adjusting clutch pedal play, inspecting for leaks in hydraulic clutch systems, and ensuring the transmission fluid is in good condition (for manual transmissions).
- Clutch Material: The quality and type of materials used in the clutch components can affect its durability. Higher-quality clutches may last longer than lower-quality ones.
- Driving Conditions: Frequent stop-and-go city driving or driving in hilly areas can put additional stress on the clutch and potentially lead to a shorter lifespan compared to primarily highway driving.
- Driver Experience: Experienced drivers who are proficient in operating a manual transmission tend to put less stress on the clutch, which can extend its life.
- Proper Break-In: If a new clutch is installed, it’s essential to follow the manufacturer’s break-in recommendations. Properly breaking in a new clutch can impact its overall durability.
Ultimately, the lifespan of a car clutch is subject to a combination of these factors, and it can be challenging to predict precisely how long a clutch will last in any given vehicle.
Regular inspection, maintenance, and driving with care can help maximize the clutch’s lifespan and ensure it performs optimally throughout its life.
If you suspect clutch problems or experience signs of clutch wear (such as slipping or difficulty shifting), it’s advisable to have the clutch inspected and serviced by a qualified mechanic.
FAQs.
Q: When should I press the clutch while driving?
This is a vague question. However, it all depends on the speed you’re traveling and whether you’re driving downhill or uphill. These are when you need to depress your clutch;
- When changing to different gear ranges
- When slowing down
- When braking on low gears
- When shifting to 1st gear
Q: Can you drive a car without a clutch?
As explained earlier, the clutch engages and disengages the engine’s rational force from the transmission.
Driving with a defective and no clutch on a manual transmission can be tricky and lead to catastrophic damage to the transmission. However, you can run without a clutch in an emergency and for a short period.
Q: Is it bad to press the clutch?
The driver can smoothly engage and disengage the transmission by depressing the clutch pedal. This means pressing the clutch is not bad.
However, some habits or situations make pressing the clutch bad. The following are driving habits that can cause severe damage to your transmissions;
- Depressing the clutch at a spotlight
- Changing gears slowly. That is lingering when stepped on the clutch pedal
- Depressing the clutch pedal while accelerating the engine to 4,000 to 5,000 RPM
- Riding the clutch. This means partially stepping on the clutch while driving
Ensure you step only when shifting to different gear ranges. Do not ride the clutch while driving. Depressing the clutch pedal when you’re not supposed to, even for the shortest time, will cause accelerated component wear.
Q: Are clutches expensive to replace?
Several factors affect clutch replacement cost. These factors include vehicle make and model, whether it is a hydraulic clutch or not, the mechanic handling the job, your location, and whether it is a manual or automatic transmission.
In any case, the average amount of clutch replacement is between $1,100 to $1,200. The parts should be between $600 to $650, while the service fee estimation is $500 to $550. However, your location can cut down the cost to $750.
In some cars, you have to pay around $350 for the replacement parts. The replacement cost will be reduced if the mechanic will not change all the clutch components.
Q: What happens if you change gears with a clutch?
Changing gears without depressing the clutch will emanate car clutch problems. If you form this as a habit or you do it for a long time, it will cause catastrophic damage to your transmission.
Q: Can a clutch fail suddenly?
A clutch can fail either suddenly or gradually. Sudden clutch failures are usually caused by the failed hydraulic master cylinder or loose, bent, or broken clutch cables/rods.
There might be a sudden fluid leak in the hydraulic system, or the disc surface may have accumulated dirt and debris.
Q: Should I press the clutch while turning?
Shift to lower gears and maintain that range throughout the turning. Always shift to lower gears when making a turn instead of depressing the clutch pedal.
Aside from using engine braking, shifting to lower gears before making turns keeps you at a required RPM, which guarantees a smooth return to high speed after the turning.
Q: How long should a clutch last?
It all depends on your driving habits and styles. Most clutches can travel over 60,000 miles before needing replacement, while some can last only 40,000 miles. Others might wear off before 30,000 miles, which is abnormal.
If you use your baby ride for inter-state travel or cruising on the highways, the clutch will last much longer than another driver who’s doing city stop-and-go driving.
Final word
Having answered the question ‘What does a clutch do’ and explained clutch problems and solutions, and the signs of a bad, you have to watch out for the outlined clutch symptoms above and fix any problem before it causes damage to your transmission.
Regardless of how useful the clutch application is, only apply it when necessary. Do not ride on the clutch for any reason except when driving in 1st gear.
If you want your clutch to meet or even exceed your lifespan expectation, follow our driving habits tips to prevent premature component wears.