Driver Knowledge Tests

What happens when your clutch fails?

The clutch is the mechanical connection between the gearbox (transmission) and the engine. It is engaged and disengaged using the left-hand pedal – push the pedal down and it disengages, release it and it engages. Without a clutch, it is almost impossible to get a vehicle moving, and it’s much more difficult to change gears as the driver must match the engine speed with the road speed. This is something that drivers do with non-synchro gearboxes such as Eaton’s Roadranger (it’s called ‘floating the gears’, and it’s not recommended), but it’s not something your average car, ute, motorbike or light truck driver would do.

How long should your clutch last?

In most standard vehicles, a clutch will last 80,000-150,000km. However, if you pull a heavy load such as a boat, do a lot of driving in stop-start traffic or you have poor clutch technique (e.g. riding the clutch, or resting your foot on the clutch while driving), then it will wear out sooner.

What are the signs the clutch is about to fail?

  • The clutch feels spongy, loose, or you can feel a vibration through the pedal
  • You hear a new noise when the clutch pedal is depressed – sometimes a squeaking noise
  • When you push the accelerator, the engine revs, but you don’t increase speed
  • You’re pushing the clutch all the way in, but it’s difficult to change gear
  • You notice fluid under the car – check it’s not from the clutch or gearbox.

What does it mean when the clutch fails?

Clutches are operated either by a cable (most common on motorbikes and cheap, small cars) or hydraulically.

Usually, this means that either the cable that operates the clutch has failed, or the clutch is worn so much that it slips constantly and doesn’t provide any forward motion.

In the first case, the clutch can’t be moved – the pedal will go to the floor, or (on a motorbike) the lever will move very easily – whereas in the second case, the clutch can be moved, but there is no material remaining on it to provide friction and therefore drive to the gearbox.

When the clutch is wearing out, it will start to slip and you may notice a burning smell as the friction pad wears down and eventually it’s metal on metal. You can tell if a clutch is slipping because the revs will rise but you won’t gain speed. Note that if you have a CVT (continuously variable transmission), these will rev like your clutch is slipping, but it’s perfectly normal for that type of gearbox.

What do you do if your clutch fails while driving?

If the clutch cable or hydraulic cylinder fails, then you will be able to continue driving as long as you can keep the vehicle moving, although it’s recommended that you pull over as soon as possible and call a breakdown service. If you are travelling where there are traffic lights, this means anticipating the lights so you can keep rolling. You will be able to change gears by matching the revs – this means giving a few more revs on the downshifts and letting the revs fall on the upshifts.

It’s unlikely the clutch will immediately fail through slipping while driving as you’ll get plenty of warning, but the clutch cable or hydraulic system is usually an immediate fail.

What vehicles don’t have a clutch?

Automatic vehicles have a torque converter, not a clutch. This enables the car to come to a complete stop while in gear, which isn’t possible in a car with a manual gearbox as the engine will stall.

Electric vehicles don’t tend to have clutches, although some EVs do have two gears.

Darren is an expert on driving and transport, and is a member of the Institute of Advanced Motorists

Posted in Advice

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