How A Vehicle Clutch Works

Clutches - The Basics

What Is A Clutch?

a complete clutch cut out from its background laid out at a slight angle

The clutch in a modern vehicle sits between the engine and gearbox. A clutches primary function is to transmit or prevent transmission of drive from the engine to the gearbox.

The Three Main Components

On most cars a clutch consists of 3 main parts; the pressure plate, the friction plate and the thrust bearing. The pressure plate is bolted to the engine flywheel. The friction plate sits between the engine flywheel and the clutch pressure plate. Typically the clutch fork is either hydraulic or cable operated from the drivers clutch pedal.

The Clutch’s 3 Jobs

To engage drive to the vehicle gearbox
To disengage drive to the vehicle gearbox
To allow smooth standing starts through clutch control which partially engages allowing the clutch to slip.

How A Clutch Works

It’s All About Drive Transmission!

When the clutch is disengaged (drivers clutch pedal up) the friction plate face is pressed against the flywheel face by a very strong diaphragm spring allowing engine drive to be transmitted through the clutch friction plate and thus transmitting drive to the gearbox input shaft which is splined into the middle of the friction plate.

When You Press Your Pedal

When the clutch pedal is pressed to the floor the thrust bearing is forced up against the pressure plate diaphragm releasing the pressure on the clutch plate, allowing it to spin freely of the engine flywheel. Drive is no longer transmitted to the gearbox.

Lets’s Get Moving!

The clutch doesn’t just allows us to change gear. Depressing the drivers clutch pedal disengages drive transmission while we select a different gear. Or by partially engaging the clutch we can smoothly move off from stationary by varying the pedal pressure.

Consider No Clutch

four individual car dashboards showing revolutions per minute and vehicle speed enphasising the need for a clutch in a vehicle

Imagine if you could not change gear. Imagine no clutch biting point. So no uphill starts than. In fact without a clutch cars would not be usable as we might as well not have a gearbox and choose one gear like 1st, 2nd or maybe 3rd gear. 1st gear is limited to about 20 – 30 mph. But you may actually get your car moving by holding on the ignition key in start position until you are moving fast enough for the jerky motion to smooth out. you would most likely not get moving in any other forward gear.

Clutch Operation

Hydraulic Clutch Operation

a clutch master cyclinder cut out showing its resavoir and plunger extruding from its housing

As you press your clutch pedal this operates the clutch master cylinder plunger inwards forcing fluid through pipe. The slave cylinder located next to the clutch is operated from the pressurised fluid forcing the clutch fork forwards. The other end of the clutch fork now forces the clutch thrust bearing against the clutch pressure plate diaphramn. The clutch plate which is splined to the gearbox input shaft is now free and drive is disengaged.

Cable Clutch Operation

a rolled up clutch cable cut out showind the entire end to end clutch cable

As you may expect the drivers clutch pedal is connected to the clutch fork via the clutch cable which pulls the clutch fork when the clutch pedal is operated. This forces the clutch thrust bearing against the clutch diaphragm allowing the clutch plate to spin freely disconnecting drive to the gearbox.

Clutch Fork

The clutch fork rests against the clutch thrust bearing. A simple but essential component the clutch fork is attached to either a cable or a slave cylinder depending on the method of operation. When the clutch pedal is pressed the clutch fork pivots from the end mounting point.

Clutch Linkages

close up of a clutch linkgage system mount to a gearbox

While most modern car clutch linkages are self-adjusting, there are some tell-tale signs that will tell you if adjustment or replacement is required. For instance, if the clutch engages and disengages and the pedal is close to the floor of the car or the transmission "grinds" when changing gear, your clutch probably needs attention. For a free clutch check or a free quote telephone us on: 0114 2363617

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