How Does The Clutch Work?

In automatic vehicles, the clutch is automated to change gears itself rather than manually in stick shifts.

If you know how to drive a stick shift car, you know the clutch is an essential component when driving. In fact, if you don’t have good clutch skills you cannot even start a manual car. The clutch is used when making a gear change and even when starting the vehicle.

Most devices have clutch systems today, from chain saws to some toys children play with.

What is a clutch?

When a car is moving and the engine is running, the car’s wheels need to be able to stop and start regardless of a running engine without killing it. Manual cars use a clutch to do this. The clutch pedal is the left most pedal.In manual cars, the clutch controls the connection between the shaft turning the wheels and the shaft coming from the engine.

For automatic vehicles, the clutch is part of the torque converter. The torque converter is a set of systems composed of the clutch and other components. It connects the engine to the vehicle’s transmission so that the wheels can turn.

Parts of the clutch

The clutch has four major components:

  • The cover plate (includes a diaphragm spring): This is connected to the flywheel.
  • The pressure plate: Exerts pressure on the driven plate through the diaphragm or coils in older vehicles.
  • The driven plate: Runs between the flywheel and pressure plate.
  • Release bearings: When the release bearings are pushed against the diaphragm spring using hydraulics or cable, it releases the spring load to interrupt power transmission.

How the clutch works

When you press your foot against the clutch pedal in a manual car, there are springs that apply pressure on the clutch disk which presses the fly wheel. This locks the engine to the transmission shaft and makes the shaft and wheels spin at the same speed.

When your foot is down on the clutch, there is a hydraulic piston pressing hard against a release fork. This release fork in turn pushes a bearing at the center of a spring.

As the center is pushed on, there are a set of pins on the outside of the spring that causes the spring to withdraw the pressure from the clutch disc. This releases the clutch from the running engine.

When the clutch is disengaged by releasing the clutch, there is arm that pushes the releasing bearing against the middle of the diaphragm spring that releases the pressure. The outer pressure plate stops clamping the driven plate. The power transmission is then broken allowing the gears to change.

For cars with a hydraulic clutch, when the clutch pedal is pressed down, a piston is activated in the master cylinder which sends pressure through the clutch fluid to a slave cylinder. The slave cylinder is connected to the release piston.

Clutch Fluid

Clutch fluid or break fluid in an essential liquid needed for the engine to function. The clutch fluid basically lasts forever as it is a closed system consisting of the reservoir, master cylinder, slave cylinder and tubing. As long as nothing goes wrong in the system, it should last forever with topping up only being required when levels are low.

To check the level of brake fluid in your car, follow the simple steps below.

  1. Turn off the engine and pop the hood
  2. Find the clutch fluid reservoir almost at the back of the engine
  3. Open the cap carefully as clutch fluid can be corrosive. A better alternative would be to use heavy rubber gloves. Also be careful with the fluid spilling on your car’s body.
  4. Check the fluid level. The clutch fluid should be full to the top, or close to full. If not, refill it. You can also use a dipstick to know the exact point the fluid is at.

Usually the level should go low after a long time. If you keep finding low fluid levels, it could be possible that you have a leak. Leaks can be serious if not discovered on time and render the clutch pedal useless. Leaks occur mostly in the cylinders (master and slave). To identify low fluid levels, there are a few symptoms to look out for.

The vehicle vibrating when changing gears. The gears should shift smoothly when the car is in good condition. Vibrations and other stutters is a likely sign of low transmission fluid. This is because low fluid makes it difficult to fully shift gears.

Gear Slip. A gear slip is when the gear fails to engage. You should not struggle to shift gears and when you find yourself engaging a gear with difficulty, it is an indication of low transmission fluid.

The vehicle lurching: Low fluid levels cause the vehicle to thrust forward or backwards when driving. It makes the ride rough and not enjoyable.

No springing effect on the clutch pedal. The clutch pedal should spring forward to normal position as you slowly release it when shifting gears. This helps in finding the clutch’s point of engagement. When the fluid is low, the pedal’s movement is interrupted. It gets stuck before reaching the furthest point or simply does not spring into normal position.

Grinding noise: Low fluid level causes a grinding noise as there is no lubrication. This noise indicates that you should top up your fluid levels immediately.

Common clutch problems

Clutches are built to last about 80k miles with good vehicle maintenance. If you carry heavy loads constantly or simply fail to service your car regularly, that lifespan could be cut to up to half. A few clutch problems you might experience are:

  • Wear and tear. This is when the material on the disc wears out because of friction
  • Slipping clutch. As the material on the plates wear out due to friction, you will notice the clutch slipping. The clutch will lose its ability to transmit rotational power from the engine to the gearbox to the wheels.
  • Hard clutch: A hard clutch means that you will require t apply a significant amount of pressure on the pedal for it to engage. This problem is caused by many components from low fluid levels to problems in the pedal linkage.
  • Leaks in the cylinders are a common problem. They reduce pressure causing serious problems like gear slips and hard clutch.
  • Air in the hydraulic system. When air gets in, pressure is lowered in the cylinders causing some problems is engagement of the gears.
  • Broken cable. The cable is used in a push-pull mechanism used by the cutch system. When it breaks, the clutch fails
  • This is when the pedal linkage transmits a less or more force than required.

How to avoid wearing out the clutch

Even though the clutch will eventually wear out, proper maintenance goes a long way to ensure it goes a while before completely wearing out. Here are a few proper maintenance tips.

Avoid riding the clutch. Riding the clutch is when you still press on the clutch (whether partially or fully) even when a gear is engaged and moving smoothly. This causes more friction on the clutch plate meaning more wear and tear.

Use the handbrake to park/when in park. When you come to a long stop, use the hand brake and release the clutch. This is because parking using the clutch puts pressure on the clutch.

Change gears properly. This is a skill that requires experience and practice. To change the gear well, you need to know the clutch’s point of engagement. You will instinctively know this point the more you drive. When you change the gears at any other point (when clutch is not deep enough or too deep), you put a strain on the clutch. Also, reduce the amount of unnecessary gear changing.

Conclusion

The clutch is one of the most important component of the engine. It is expensive to repair. You should constantly service it to ensure its longevity and smooth working.

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