High-end supercars such as the Lamborghini Aventador may use paddle shifters near the steering wheel instead of a clutch, but most cars with manual transmissions involve the use of a pedal to shift gears. Anyone who drives a stick shift car will likely think nothing of the third pedal at their feet, but a lot goes into engaging and releasing the clutch under the hood.
There is a flywheel connected to the engine, and this is held in place by a clutch plate, which is hooked up to the transmission. A pressure plate is fitted on the outside of the clutch plate to hold it against the flywheel when the car is in gear. After the pressure plate is in place, a diaphragm spring pushes the pressure plate against the clutch disc when your foot is off the clutch. The throw-out bearing holds everything in place so the transmission spins with the engine when the clutch is released.
Engaging the clutch by applying pressure to the pedal pushes the throw-out bearing in against the center of the diaphragm, which forces the outer edges to bow away from the engine. In turn, the pressure plate is pulled away from the clutch disc and the transmission is disconnected from the engine.
Like any other car part, the clutch is subject to developing problems and wear. The most common issue that arises with the clutch is worn friction material. This material is located on the clutch disc and the flywheel so they spin in sync. When the clutch slips, or does not fully engage, this can cause unnecessary wear.
Slipping is one common issue that arises with a clutch, but things can go wrong in the other direction as well. A sticking clutch can make it difficult to switch gears, and if you notice a grinding noise when you shift, this could be due to a clutch that is literally sticking to the flywheel. There are a few different things that can cause the clutch to stick.
A sticking clutch may be due to leaking cylinders, which are otherwise responsible for controlling the throw-out bearing. There may also be air in the hydraulic lines that will cause a loss of pressure. Broken or worn clutch cables and misadjusted linkage can also cause the clutch system to malfunction, which can trap the clutch disc against the flywheel.