Regular car, truck, and motorcycle maintenance and inspection can often prevent or catch problems before they become catastrophic. However, it’s relatively easy to inspect your brakes or check your oil level. Not every vehicle component is so easily examined, especially the transmission. And apart from the transmission fluid—which isn’t actually a ‘lifetime fluid’—there’s one component that needs attention from time to time: the clutch.
How does a clutch work?
As Donut Media and CJ Pony Parts explain, to get power to a wheel, it has to travel from the engine’s crankshaft through the transmission and driveshaft, and into a differential. But you can’t change gears just by moving the shifter. The engine and driveshaft turn at different speeds, and shifting like that would severely damage the transmission. That’s why there’s a clutch.
At its heart is a disc made of high-friction material. This disc presses up against the flywheel, which is connected to the engine’s crankshaft. A pressure plate and diaphragm spring maintain even pressure on the disc, with the whole arrangement contained with a cover bolted to the flywheel. All this is mounted on an input shaft. As the crankshaft turns, it spins the flywheel, which spins the disc, which spins the input shaft, which feeds into the transmission.
When you want to change gears, you press down on the clutch pedal, which depresses a release (or ‘throw-out’) bearing. This presses on the diaphragm spring and disengages the friction disc. With this, the transmission gears can spin freely, and you can shift. When you’re down, you release the clutch pedal, which releases the bearing and thus the spring. The friction disc reengages, and smoothly lets the transmission and driveshaft reconnect with the engine.
Does every vehicle need a clutch replacement?
Like brake pads, a clutch is a mechanical component that gradually wears away, especially the friction disc. As such, it needs to be replaced after a set number of miles. However, so far, we’ve only discussed a manual transmission. It’s a slightly different story with dual-clutch transmissions and automatics.
A dual-clutch, as the name implies, uses two computer-controlled clutches to shift gears. This, Autotrader explains, speeds up shifts and prevents excessive loss of power and acceleration. They were marketed as smoother than manuals and faster than conventional automatics, however, as the Ford Focus’ DCT has shown, that’s not always the case.
In fact, Car and Driver reports automatics have improved so much, the DCT is becoming overshadowed from a performance standpoint. The Koenigsegg Revera hypercar, for example, uses a torque converter, not a DCT. Nevertheless, a DCT has conventional clutches, and these too do occasionally need to be replaced.
A torque converter automatic, however, doesn’t have a clutch like a manual or DCT does, Autoblog explains. Instead of a friction disc, a torque converter uses spinning fans and fluid to send power from the engine to the transmission. That’s why Matt Farah’s 1,000,000-mile Lexus LS400 could last that long without needing major transmission repairs: no clutch to replace.
There is a kind of clutch inside the torque converter, CJ Pony Parts explains. However, Car Treatments and Mechanic Base explain that if your torque converter’s having clutch problems, it’s cheaper and easier just to replace the whole converter.
Clutch care and warning signs
With the proper care, CarBible reports a friction disc can last up to 100,000 miles. Some can last even longer, though. Motor1 reports a 1994 Acura Legend LS has traveled over 570,000 miles on its original clutch. Motorcycle clutches generally don’t last quite as long as car clutches, but you should be able to go multiple riding seasons without worry.
The biggest factor in clutch wear is the driver or rider, Your Mechanic explains. Keeping the clutch pedal or lever depressed for extended periods puts strain on the components, Click Mechanic explains, for one. So, does ‘riding the clutch’, i.e. letting it out too slowly, and causing excessive drag on the friction disc.
There are several signs that indicate your clutch may be on the way out. One of the first, CarBible explains, is if the pedal or lever moves with less resistance than normal. That means the friction materials is starting to lose its grip. If this continues, the clutch can start to slip, letting the engine rev without the vehicle moving, which can sometimes result in literally burning the clutch up. This also occurs in motorcycles, though Motorcyclist reports a frayed or stretched clutch cable can also cause clutch slip.
You can also have the opposite problem: the clutch sticking too much, or failing to release. When this happens, you’ll hear a loud grinding noise, feel lots of vibration, and possibly detect a burning odor.
The bearings can also fail, CJ Pony Parts reports. That’s indicated by squealing or chirping when the pedal or lever is depressed. And if your car or bike is noisy in neutral, but quieter in gear, that might be the input shaft bearing that’s in need of replacement.
Is this a DIY repair?
Changing your own clutch can be done, Autoweek reports. However, the repair involves dropping the transmission from the car, not something every home mechanic is comfortable with. And if you suspect a torque converter failure, CarBible reports, that’s a repair best suited to a trained professional.
But, if you keep a weather eye out for the warning signs, you should be able to get your clutch changed before any further damage is done.
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