Technology for transmission continues to advance ahead at a rapid speed, especially in terms of automated gearboxes, however manual gearboxes aren’t drastically changed since the idea of multiple speeds for a rotating machine emerged in the early 1900s. Modern vehicles have synchromesh, and some also come with rev-matching functions however, all without fail use the same type of clutch and it’s a resaleable item therefore it’s important to be aware when it needs attention.
What does a clutch do?
In simple way, the clutch sends energy from an engine into the gearbox but more importantly, it can isolate it from its gearbox to allow changing of gears within the gearbox. The clutch plate itself is usually made mostly of metal trimmed in a friction material on both sides. It has a splined centre section, which permits it to slide along the input shaft of the gearbox. In its default position (i.e. without the clutch pedal pressed), it is clamped against the flywheel by the pressure plate of the clutch. It is not possible to slip this way.
When you press the clutch pedal it disengages the clutch so power is interrupted. Some vehicles use an electronic clutch cable that pulls an internal lever in the gearbox (called”the release bearing fork) and, in turn, moves the release bearing into between the plates. In the middle, a diaphragm lets the clamping pressure go, meaning the clutch plate is no longer held by the flywheel, and it is able to rotate at a different speed depending on the gear chosen, etc. The clutch is able to be’slipped depending on the extent to which the pedal for the clutch is pressed. Although the basic principle is the same, other vehicles make use of hydraulics instead of a cable for the clutch, where the pedal movement is controlled by a master cylinder which changes the hydraulic pressure to a slave cylinder. This then determines the motion of the release bearing fork.
How do you know if your clutch needs to be replaced?
Clutch Slip
With time, the friction material on the clutch wears out and when that happens the clutch will start to slide. It should be quite obvious when your car’s clutch is sliding when it shouldn’t. If the clutch pedal is completely removed (i.e. not pressed at all) and the clutch pedal is not pressed at all, there should be no slip whatsoever. Slip is evident by the sudden increase in engine revs without any associated acceleration when your vehicle has been in gear and and the clutch pedal isn’t pressed when you press the accelerator pedal. It can also be evident when you try to accelerate up a steep climb. Even though the degradation of a clutch takes place slowly as time passes (depending on the type of driving you do and the conditions – stop-start traffic is known to wear down clutches more quickly than, say motorway driving) If it’s slipping in this manner then it’s the perfect time to replace it. There are other signs to look out for and look out for, like strong smells emanating from the engine as you move away from the stop or an increased “bite” point on the clutch pedal than prior to.
It could also mean that something is wrong in the hydraulics of your clutch (if you car has an automatic clutch that is hydraulically operated). The first step is to check that the master cylinder reservoir (in the engine bay and looks like the brake fluid reservoir) is topped up with clutch fluid. If everything is fine, it’s time to take the car to a garage for determine if the slave’s cylinder is in need of replacement. In cars that use a clutch cable instead of hydraulic activation, the cable may stretch, and isn’t an expensive or complicated component to replace.
Clutch Judder:
The most obvious sign of juddering is when setting off from a stop. It is manifested as a powerful vibrating
by the engine/transmission as you let the clutch go to get the car moving. It’s typically something like hydraulic fluid or oil that has somehow found its way onto the outside of the clutch and causes it to not grasp properly or smooth when it is engaged, creating a feeling of juddering as it grips at times, it slips and then grabs the same place and it goes on and so on. It can also result from misalignment or misalignment the flywheel, or by the clutch being slightly warped or just getting worn out or stained to the point the clutch isn’t getting consistent grip. The judder in the clutch can be extremely severe, so much so that it can make the car difficult to navigate, especially in rush hour. It’s also extremely annoying to endure! The only way to stop clutch judder would be to have it replaced.
Worn Release Bearings & Double Mass Flywheels:
I’ve placed these two components together as they are very different, when they begin to fail they can have very similar sounds. If you hear the sound of a low rumbling from the gearbox which fades disappear when you press your clutch pedal then it’s possible you have an issue with the release bearing or the double mass flywheel (if your car is equipped with one)
Other Issues: There are also several clutch-related problems that might not be solely the fault of the gear itself. Sometimes the problem is not caused by slipping, but sticking. If your clutch doesn’t release properly it will continue to turn the input shaft. This can result in grinding or completely stop your car from going into gear. The most common reasons why the clutch could become stuck are:
Damaged or stretched clutch cable The cable must have the proper degree of tension in order to push and pull effectively.
A defective or leaky slave and/or master clutch cylinders. Leaks stop the cylinders in the process of building the necessary amount of pressure.
Aeration in the lines of the hydraulic Air can affect the hydraulics by filling up the space that the fluid requires to build pressure.
Misadjusted linkage – When your foot hits the pedal it transmits the wrong quantity of force.
If you’re encountering any of the above symptoms , you may be lucky and not have to replace your clutch in any way, it may be something that is simple and cheap to fix!
Replacing the clutch on your car.
It’s required in almost every vehicle (there are a few exceptions) to take the gearbox out of the vehicle for the purpose of replacing the clutch, which is why it’s such a costly and time-consuming job to finish – regardless of the price of the parts themselves. Thus although it’s usually only the clutch plate that requires replacement, it’s still worth purchasing the entire kit, which includes the pressure plate as well as the release bearing. If you’re planning to undertake van clutch replacement yourself, make sure you are aware of the procedure, consult a workshop manual if necessary and stay in a safe place.
A note on dual-mass flywheels.
Much is said regarding dual mass flywheels. They are effective in reducing vibrations in cars that generate large torque at low speeds, but can cause issues in all models based on the type of driving it is predominantly used for. The mechanism is weakening and breaking into pieces over time, leading to slow starting and poor running. If you’re replacing your dual-mass flywheel, make sure you replace the remainder of the clutch, since the gearbox will be removed in any case. Beware this: it’s an extremely popular change for certain cars to convert from a dual mass flywheel to a solid flywheel. Most often, it’s because they’re cheaper, but mostly because dual mass flywheels get lots of negative press regarding reliability, but they’re designed for a reason and replacing yours with a solid conversion will cause a significant increase in the vibrations through the clutch pedal and the cabin in general.
