What happens when you replace a clutch

Replacing a clutch means removing the old friction disc, pressure plate, and related parts from between your engine and transmission, then installing new ones. The job takes a mechanic four to eight hours on most cars, though some vehicles require removing the engine or transmission to reach the clutch, which can add time and cost.

You'll know the clutch is worn when the pedal feels spongy or sinks to the floor, the car struggles to move forward even with the engine running, or you smell a burning smell when shifting. A worn clutch won't grip the engine's power anymore, so the wheels won't turn even though the engine is spinning.

This is not a job most home mechanics attempt without a lift and specialized tools. The transmission or engine has to come out, and the clutch sits in a tight space where you can't see or reach it easily. If you're comfortable with basic car work but have never done this, this guide will help you understand the process and what to expect when you take the car to a shop.

Key Takeaways

  • A clutch replacement requires removing either the transmission or the engine to access the clutch assembly, which is why most people take the car to a mechanic.
  • The job involves unbolting the pressure plate, removing the worn disc, installing a new disc and pressure plate, and adjusting or replacing the throwout bearing.
  • On most cars, a mechanic will also replace the pilot bearing and inspect the flywheel for damage while the transmission is out.
  • The total cost ranges widely depending on the car model and whether the flywheel needs resurfacing, but labor is usually the largest expense.
  • If you do attempt this at home, you will need a transmission jack, engine hoist, socket set, and a clutch alignment tool to keep the new disc centered.

Removing the transmission or engine

Before you can touch the clutch, the transmission has to come out. On most cars, you'll disconnect the battery, drain the transmission fluid, unbolt the driveshafts or axles, and remove the shifter linkage and clutch cable or hydraulic line. Then you'll support the engine with a jack or hoist and unbolt the transmission from the engine block.

Some cars are easier to work on if you remove the engine instead. This is common on front-wheel-drive vehicles where the engine and transmission are bolted together as one unit. You'll disconnect the radiator hoses, fuel lines, and electrical connectors, then lift the whole assembly out. This takes longer but sometimes gives you better access to the clutch.

The transmission or engine will be heavy—usually 100 to 300 pounds—so you must use a proper jack or hoist rated for the weight. Resting it on a floor jack alone can be dangerous. Many shops use a transmission jack, which has a cradle that holds the transmission steady while you unbolt it.

Unbolting the pressure plate and removing the old disc

Once the transmission is out, you can see the clutch. It sits on the back of the engine, bolted to a large spinning wheel called the flywheel. The pressure plate is bolted to the flywheel with six to eight bolts arranged in a circle.

Loosen these bolts a little at a time, going around in a star pattern (opposite bolts alternately) so the pressure plate comes off evenly without warping. If you loosen one side all the way first, the plate will tilt and stick. Once all the bolts are out, the pressure plate and old friction disc will come free.

The friction disc is the thin, round part that looks like a small brake rotor. It has a splined center hole that slides onto a shaft called the input shaft. Once the pressure plate is off, the disc will fall out—catch it so it doesn't drop on your foot or the engine.

Inspecting and preparing the flywheel

Before you install the new clutch, look at the flywheel surface where the friction disc spins against it. It should be smooth and shiny. If it's scored, cracked, or has a glazed (shiny, slippery) surface, it needs to be resurfaced or replaced.

Resurfacing means taking the flywheel to a machine shop where they'll use a lathe to cut a thin layer off the surface, making it smooth again. This usually costs $75 to $150 and takes a day or two. If the flywheel is cracked or too thin to resurface safely, you'll need a new one, which costs $200 to $400 depending on the car.

Many mechanics resurface the flywheel as part of a clutch job because a worn flywheel will wear out the new clutch faster. If you skip this step to save money, you may find the new clutch doesn't last as long as it should.

Installing the new clutch assembly

The new clutch kit usually includes a friction disc, pressure plate, and throwout bearing. Some kits also include a pilot bearing, which is a small bushing that supports the input shaft where it enters the engine.

Start by installing the pilot bearing if it's included. It presses into the center of the flywheel. You'll need a pilot bearing installer tool or a socket that fits snugly inside it—tapping it in with a hammer risks damaging it.

Next, slide the new friction disc onto the input shaft. It will only fit one way because the splines are cut at an angle. Use a clutch alignment tool—a tapered shaft that holds the disc centered while you bolt the pressure plate back on. Without this tool, the disc will be off-center and the transmission won't slide back on smoothly.

Bolt the pressure plate to the flywheel using the same star pattern you used to remove the old one. Tighten the bolts to the torque specification in your car's service manual, usually between 15 and 25 foot-pounds. Over-tightening can warp the pressure plate; under-tightening means it won't grip properly.

Replacing the throwout bearing and adjusting the clutch

The throwout bearing (also called the release bearing) is a small bearing that presses against the pressure plate fingers when you push the clutch pedal. It wears out along with the clutch and should be replaced at the same time.

The bearing bolts or slides onto a shaft called the input shaft sleeve. Remove the old bearing and slide the new one on, making sure it seats fully. Some cars have a hydraulic throwout bearing, which is a cylinder that does the same job—if yours has one, you may need to bleed the hydraulic line after installation.

Once the new bearing is in, reinstall the transmission, reconnect all the hoses and electrical lines, and fill the transmission with fresh fluid. If your car has a hydraulic clutch, you'll need to bleed air out of the line by pressing the pedal repeatedly while opening a small bleeder valve on the slave cylinder until only fluid comes out, no bubbles.

Testing the new clutch before driving

Before you take the car on the road, test the clutch in the driveway. Start the engine and slowly release the clutch pedal while in first gear without pressing the gas. The car should move forward smoothly without jerking or stalling.

The pedal should feel firm and return to the top when you release it. If it feels spongy or sinks slowly, there may be air in the hydraulic line or the cable may need adjustment. If the car jerks or the pedal is very high or very low, the throwout bearing or pressure plate may not be seated correctly.

Drive slowly in a parking lot and practice shifting up and down. The clutch should engage smoothly without slipping (the engine revving without the car speeding up) or grabbing (the car lurching forward). If something feels wrong, stop and check your work before driving on the highway.

Common mistakes to avoid

The most common mistake is not using a clutch alignment tool. Without it, the friction disc sits off-center, and the transmission input shaft won't slide into the splines smoothly. You'll force it, damage the splines, and have to do the job again.

Another mistake is not resurfacing the flywheel. A worn flywheel will wear out the new clutch in half the time, and you'll be back under the car in two or three years instead of five or more.

Tightening the pressure plate bolts unevenly or all the way on one side first will warp the plate and cause the clutch to chatter or slip. Always use a star pattern and tighten a little at a time.

Forgetting to bleed the hydraulic line on cars with hydraulic clutches will leave air in the system, making the pedal feel spongy and the clutch not engage fully. Bleed the line before you consider the job done.

Frequently Asked Questions

How long does a new clutch last?

A new clutch on a car driven normally lasts 50,000 to 100,000 miles. Drivers who ride the clutch, tow heavy loads, or drive in stop-and-go traffic may see the clutch wear out in 30,000 to 50,000 miles. A resurfaced flywheel and a quality friction disc will extend the life.

Can I replace just the friction disc without the pressure plate?

It's not recommended. The pressure plate wears at the same rate as the friction disc, and replacing only the disc leaves a worn pressure plate that will wear out the new disc quickly. Replacing both together costs only slightly more in parts but saves you from doing the job again soon.

What's the difference between a single-disc and dual-mass flywheel?

A single-disc flywheel is a solid wheel that bolts to the engine. A dual-mass flywheel has two wheels connected by springs to absorb vibration and reduce noise. Dual-mass flywheels are more expensive to replace but last longer on modern cars. If your car came with one, replace it with the same type.

Do I need to replace the clutch cable or hydraulic line?

Only if it's damaged or leaking. If the cable is frayed or the hydraulic line is cracked, replace it while the transmission is out—it's much harder to reach once everything is bolted back together. A new cable costs $30 to $80; a new hydraulic line costs $50 to $150.

What if the car won't go into gear after I reinstall the transmission?

The friction disc is probably off-center. You'll need to remove the transmission again and use a clutch alignment tool to center the disc before bolting the pressure plate back on. This is why using the tool the first time is so important.