Clutch – description and check

1. All vehicles with a manual transmission have a single dry plate, diaphragm spring-type clutch. The clutch disc has a splined hub which allows it to slide along the splines of the transmission input shaft. A sleeve-type release bearing is operated by a release fork in the clutch housing. The fork pivots on a ballstud mounted inside the housing.

2. The clutch release system is operated by hydraulic pressure. The hydraulic release system consists of the clutch pedal, a master cylinder and fluid reservoir, the hydraulic line, a release cylinder, and a release fork mounted inside the clutch housing.

3. When force is applied to the clutch pedal to release the clutch, hydraulic pres­sure is exerted against the release fork by the release cylinder pushrod. When the release fork is moved, it pushes against the release bearing. The bearing pushes against the fin­gers of the diaphragm spring of the pressure plate assembly, which in turn releases the clutch plate.

4. Terminology can be a problem when discussing the clutch components because common names are in some cases different from those used by the manufacturer. For example, the driven plate is also called the clutch plate or disc, the clutch release bearing is sometimes called a throwout bearing, and the release cylinder is sometimes called the slave cylinder.

5. Unless you’re replacing components with obvious damage, perform these prelimi­nary checks to diagnose clutch problems:

a) The first check should be of the fluid level in the master cylinder. If the fluid level is low, add fluid as necessary and inspect the hydraulic system for leaks.

b) To check clutch spin-down time, run the engine at normal idle speed with the transmission in Neutral (clutch pedal up – engaged). Disengage the clutch (pedal down), wait several seconds and shift the transmission into Reverse. No grind­ing noise should be heard. A grinding noise would most likely indicate a bad pressure plate or clutch disc.

c) To check for complete clutch release, run the engine (with the parking brake applied to prevent vehicle movement) and hold the clutch pedal approximately 1/2-inch from the floor. Shift the trans­mission between 1st gear and Reverse several times. If the shift is rough, com­ponent failure is indicated.

d) Visually inspect the pivot bushing at the top of the clutch pedal to make sure there’s no binding or excessive play.