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Parts of a Car Clutch System and How They Function

Nov. 16, 2023

While driving your vehicle and accelerating, the clutch system plays a pivotal role in transferring power from the engine's crankshaft to the transmission. Without this system, power would consistently flow to the transmission, resulting in constant forward propulsion of the wheels. Hence, a crucial component is required to enable disengagement of the engine's power from the rest of the powertrain, allowing drivers to maintain control over the vehicle's speed.

Essentially, a clutch comprises a metal disc embedded with friction material, similar to brake pads. When there's no pressure exerted on the clutch, it operates freely, allowing independent rotation. However, upon the application of pressure, the clutch engages with another component, enabling them to rotate at synchronized speeds. This fundamental mechanism forms the basis of how a car clutch functions during operation.

Although clutches may be present in various mechanisms, their consistent location is within a transmission system. In the case of a manual transmission, the clutch is situated between the engine's crankshaft and the transmission housing, specifically positioned on an input shaft housed within the bell housing. On the contrary, within an automatic transmission, a sequence of clutches can be found housed inside the transaxle assembly.


What's the difference between manual and automatic transmission?


Regardless of whether you have an automatic transmission or a manual gearbox, both rely on clutches to enable control over your vehicle for acceleration, deceleration, and braking. Without a clutch, your engine would stall every time you come to a halt!

However, there are several key differences between manual and automatic transmissions:

1. In a manual transmission, there's typically one large clutch disc, whereas automatic transmissions comprise a series of smaller clutches.

2. The clutch disc in a manual system operates dry, while in an automatic transmission, the clutches are immersed in oil.

3. Engaging the clutch disc in a manual transmission involves using a clutch pedal, whereas the torque converter in an automatic transmission initiates the engagement of its clutches.

4. During a rebuild, clutches in an automatic transmission are serviced, while in a manual transmission, the clutch is replaced as part of routine maintenance.

Now, let's delve into the primary components of a manual transmission's clutch system and explore their functionalities.


Clutch main parts and their functions


While there are many related parts, these eight parts are the major players in a clutch system on a manual transmission.

Clutch Disc:

At the heart of the system lies the clutch disc, a substantial circular component typically exceeding 30 cm in diameter. It seamlessly fits onto the transmission's input shaft, featuring bonded friction material on both of its flat surfaces, akin to the semi-metallic composition found in brake pads. Upon pressing the clutch pedal, the disc rotates freely, disengaging power transfer between the transmission and the engine. Upon release of the clutch pedal, it gets compressed between the flywheel and the clutch pressure plate, aligning the transmission's rotation with the engine speed.

Most clutch discs are 'sprung', incorporating a torsion damper affixed with springs. These springs serve to absorb a significant portion of vibrations stemming from the powertrain, consequently enhancing the smoothness of your drive.

 Clutch Disc

Clutch Pressure Plate:

Positioned opposite the engine side of the clutch disc, the clutch pressure plate serves the purpose of releasing pressure from the clutch when the pedal is depressed. Its central metal fingers function as springs. Upon compression, these springs actuate a pressure disc, thereby disengaging it from the friction material.

 Clutch Pressure Plate


The flywheel is securely bolted to a flange located at the rear of the engine's crankshaft. This heavy steel plate serves several functions. Primarily, it acts as a weighted mass, reducing vibrations by balancing the engine's rotation. Additionally, the flywheel plays a crucial role in smoothing out the engine's revolutions per minute (RPM), making the engagement of the clutch less abrupt. Its primary function is to provide a surface for the friction material on the clutch disc to lock against, enabling the transmission to transmit the engine's power.


Release Fork/Release Bearing:

While the pressure plate spins at the same rate as the engine, a stationary component is required to engage it and release pressure from the clutch as needed. This task is assigned to a release fork and release bearing. When the clutch pedal is depressed, it extends a rod at the transmission to exert pressure on the release fork. Consequently, the fork utilizes lever motion to press towards the fingers of the clutch pressure plate. Positioned at the end of the clutch fork, the release bearing enables the non-rotating fork to release pressure, thus disengaging the clutch.

 Release Bearing

Slave Cylinder:

The clutch slave cylinder serves a singular function. Upon activation, a rod extends from the slave cylinder to exert pressure against the release fork. Typically, the slave cylinder operates hydraulically, although in certain instances, it might also be cable-operated.

 Slave Cylinder

Master Cylinder:

In hydraulic clutch systems, the master cylinder holds paramount importance. Positioned directly opposite the clutch pedal on a car's firewall, it plays a pivotal role. When the pedal is depressed, a piston within the master cylinder compresses fluid into the hydraulic line directed towards the slave cylinder. This hydraulic pressure activation sequence continues. Upon releasing the pedal, fluid returns to the master cylinder, prompting the re-engagement of the clutch disc.

 Master Cylinder

Clutch Pedal:

The visible component of the clutch system from inside your car is the clutch pedal. It utilizes the force exerted by your foot to initiate movement of the piston in the master cylinder. A robust spring on the clutch pedal aids in restoring it to its top position when your foot is lifted.

 Clutch Pedal

Pilot Bearing:

Although not directly a clutch part, the pilot bearing is essential and should be replaced when the clutch is changed. It typically comprises a small ball bearing or needle bearing assembly that perfectly fits into the end of the crankshaft. Serving to center the transmission and clutch, it also stabilizes the transmission with the engine by allowing the transmission input shaft to fit into its center.


Summing up how the clutch components collaborate:

1. The driver presses the clutch pedal with their foot.

2. A piston within the master cylinder propels fluid through a hydraulic line directed towards the slave cylinder.

3. The hydraulic pressure extends a rod on the slave cylinder, causing the release fork to pivot.

4. The release fork applies pressure to the release bearing, compressing it against the pressure plate springs.

5. This action releases pressure from the pressure disc, enabling the clutch disc to move freely between the pressure disc and the flywheel.

Car Clutch System

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