Q: How Does a Clutch Work?

asked by on December 01, 2015

How does a clutch work in a manual transmission?

A clutch for a manual transmission is not a single part, but many parts put together to form the clutch assembly that is part of the clutch system. The parts in a clutch assembly are the clutch pressure plate, clutch disc, clutch release bearing, flywheel, clutch release fork and pilot bearing. The clutch system consists of the clutch assembly, clutch cable, clutch pedal, and bracket. Some clutch systems use hydraulics to move the clutch instead of the clutch cable. The system has a clutch master cylinder, fluid pressure line, clutch slave cylinder, and a different release fork or no fork at all, mounted on the front of the transmission.

The clutch pressure plate is bolted to the flywheel with the clutch disc sandwiched between them. The pressure plate keeps high pressure on the clutch disc causing it to press against the flywheel. The clutch disc has material mounted to it with rivets or glue similar to brake pad material. The disc has center splines that slide on and lock to the transmission input shaft. The input shaft is supported on its tip by a pilot bearing or bushing in the center of the flywheel or rear of crankshaft. The clutch release bearing slides on the front of the transmission and is pressed on the pressure plate fingers to release its pressure on the clutch disc. This allows the engine and transmission to spin free of each other.

The clutch operation starts with the operator pressing in the clutch pedal. The pedal arm will pull in on the cable or the arm will push in on the rod to the clutch master cylinder. The cable will pull on the clutch release fork or the clutch hydraulic slave cylinder will press in the clutch fork. The fork or slave cylinder pushes in the release bearing to press on the clutch pressure plate to release the clutch. As the pressure plate is pressed, it takes off pressure on the clutch disc and allows the transmission to be shifted. Once a gear is selected, the clutch pedal is released and the pressure plate then applies pressure on the clutch disc. As pressure is applied, the clutch disc is locked to the pressure plate and flywheel to turn the transmission input shaft.

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