Car Flywheel Problems: 5 Most-Common Issues & Solutions

If your car has a manual transmission, it has a flywheel connected to the crankshaft inside the engine. The flywheel has multiple functions including starting the car and transferring engine power to the transmission.

While the flywheel is a simple design, it can complicate driving and ruin the driving experience.

We’ve gathered the most common flywheel issues and how to fix them, so you can keep a positive driving experience going in the future.

#1 – Your Car Is Hard To Start And The Starter Makes A Grinding Sound

When you jump in your car and turn the key, the last thing you want to hear is a grinding sound as you try to start the engine.

Many times the starter is the cause of the grinding sound, but that’s not always the case. Your flywheel may have a problem with the teeth, and it won’t engage with the starter correctly.

How to Fix It

The flywheel is fastened to the engine crankshaft, and it has teeth around the circumference that engage with the starter motor to start the engine.

The teeth need to mesh with the gear teeth on the starter motor otherwise you may hear a grinding sound as the teeth clash and damage each other. If the grinding is allowed to continue, it will eventually wear or break the teeth off the starter and the flywheel.

Most often the cause of the teeth clashing together is the wrong starter has been installed or the starter motor body needs to be aligned for proper engagement.

Many cars have the option for a manual or automatic transmission, and each type can require a different starter motor for proper engagement.

You may also have differences in model years of the car, and an incorrect model year could be selected by mistake causing the wrong starter motor to be installed. Installing the correct starter motor for the model year and options can easily fix this mistake.

The starter alignment doesn’t happen frequently with today’s newer cars due to quality control at the auto manufacturers. You may find alignment issues with cars and trucks from the 1980s and earlier that require shims between the starter motor housing and the engine block to correctly align the gears and teeth.

These shims are cheap at an auto parts store, and you just need to loosen the starter motor and slide the shims between the housing and the engine block. It may take two or three tries with varying shim sizes to find the perfect thickness to solve the grinding problem.

#2 – Your Car Vibrates And Makes Noises When Idling

Your clutch assembly spins at the same speed as your engine. Even at an idle speed, the assembly rotates 800-1,000 times per minute.

That’s fast!

Any imbalance or loose fasteners can cause a vibration or make a significant noise that you can hear inside the car.

How to Fix It

The flywheel is attached directly to the rear of the engine crankshaft and is meant to store rotational energy. It absorbs excess power from the engine, reduces vibrations, and keeps rotational momentum to reduce engine speed reduction when you take your foot off the pedal.

There are two types of flywheels currently in use: single-mass and dual-mass.

They are typically made from aluminum, iron, or steel, with most newer cars using dual-mass flywheels made from lighter alloys. The dual-mass type of flywheel has two separate flywheels that rotate independently of each other. One is attached to the clutch with the second attached to the engine. Each flywheel is separated and balanced by springs that dampen engine vibrations.

The clutch assembly can become worn, corrode, and warp due to overheating. The balancing springs can lose their ability to dampen vibrations and you may be able to feel them in the car. You may also hear chattering or clunking with the engine running. The springs in the dual-mass flywheel aren’t doing what they are intended for.

Flywheels may be resurfaced if the surface is warped or unevenly worn, but most often they are replaced with a new unit.

#3 – The Clutch Is Slipping

The flywheel and clutch disc surfaces use friction to work together. When one or both have worn surfaces, the clutch assembly may not transmit power to the transmission to move the car.

How to Fix It

The flywheel is attached to the engine crankshaft and will always turn when the engine is running. The clutch pressure plate is attached to the flywheel around the periphery, and it too will always rotate with the flywheel and engine crankshaft.

The key for the transmission to receive rotational power is the clutch disc must contact the flywheel and use friction to turn with the flywheel.

If your clutch is slipping, it means there isn’t enough friction between the clutch disc and flywheel surfaces. The flywheel could be warped due to overheating. The clutch disc could be worn out and the friction surface could be damaged.

The clutch disc will need to be replaced, but the flywheel may be able to be resurfaced to remove the warped surface condition. If the flywheel is too thin, or the warping has caused significant damage, the flywheel will need to be replaced also.

Read also, Car Clutch Problems: 4 Most-Common Issues & Solutions

#4 – You Detect A Burning Smell From The Clutch Area

If you drive your car harder than most, you may detect a burning smell from the clutch area occasionally. If you can smell the clutch all the time, you’re causing damage to the clutch assembly and flywheel due to overheating.

How to Fix It

When the clutch assembly is replaced, the surfaces on the flywheel and clutch disc should be cleaned before they are installed in the car. Dirty or oily surfaces can cause a burning smell as the surfaces heat up from use.

A second reason you may smell burning from the clutch and flywheel is due to overpowering the clutch disc. Poor driving habits such as shifting without using the clutch pedal, towing heavier loads than recommended, or driving with the clutch pedal partially depressed can cause excess friction and abuse between the flywheel and clutch disc.

It can wear out the clutch disc prematurely and warp the flywheel surface beyond repair.

If the burning smell is constant, you need to know why. If the surfaces were dirty when installed, they should be cleaned to prevent further smells and potential damage.

If you’re overpowering the clutch due to poor driving habits, they need to change before you cause irreparable damage.

#5 – It Is Difficult To Change Gears On The Transmission

When you depress the clutch pedal, the clutch disc should move away from the flywheel and allow you to change gears easily.

If the clutch disc still contacts the flywheel, the transmission gears will be difficult to change with the shifter lever.

How to Fix It

If the gears are difficult to change with the clutch pedal depressed, the clutch disc is still contacting the flywheel and dragging on the surface. The flywheel could be warped and the high points on the surface could be touching the clutch disc with or without using the clutch pedal.

You will need to remove the flywheel and have the surface flattened or completely replace the flywheel.

A second cause of a dragging clutch is the shifting fork not moving correctly. It should be able to move through the full stroke to fully depress the clutch pressure plate.

If the clutch slave cylinder in a hydraulic system isn’t adjusted correctly or it doesn’t move through its full stroke, it may allow the clutch disc to slightly contact the flywheel as you try to change gears.

A manual system with a cable between the pedal and shifting fork could have a cable that has stretched. A cable that is too long will not move the shifting fork through its full stroke and allow the clutch disc to contact the flywheel as you shift gears.

You will need to shim the clutch slave cylinder or replace any parts that are worn.

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