We get asked all the time what exactly does a clutch do? Why does it wear out and why is it so expensive?
The technical explanation would be something like: A clutch is a mechanical device that provides for the transmission of power (and therefore usually motion) from one component (the driving member) to another (the driven member) when engaged, but can be disengaged.
Think about it this way. While the engine on your vehicle is running there needs to be some way to disconnect the engine from the wheels. If there was no way to disconnect the engine from the wheels then starting your car would be next to impossible and every time you stopped, the engine would stall. So the clutches job is to disconnect the engine from the rest of the drive system.
So why does a clutch wear out? The most important reason is because the clutch does not instantly engage. If the clutch only had two states fully engaged or fully disengaged then getting your vehicle going from a dead stop would be quite difficult. By “slipping” the clutch, engaging it slowly, your vehicle can start off smoothly giving you a comfortable start. The clutch disk is made out of material very much like brake lining. Over time as you “slip” the clutch this material becomes worn away until eventually your clutch will no longer hold. This is when it requires replacement. To replace the clutch usually requires removing the transmission. On most vehicles this is a large job, the more labor the higher the cost.
Vehicles with more powerful engines usually have more expensive clutches. In fact very powerful vehicles such as race cars, super cars and trucks may even have a clutch which has two states; engaged and disengaged. These vehicles are very difficult to get moving from a dead stop and take a lot of practice. I have had an opportunity to drive several NASCAR cars. The first time I drove one I needed the pit crew to push the car as I could not get it moving without stalling the engine and they did not want me to spin the tires. I used to work in the heavy duty industry so have seen many broken axles and drive shafts due to inexperienced clutch operators.
Bottom line: as you gain more experience, use your clutch less and more efficiently, the longer it will last so the less it will cost you.