When your car has a difficult time starting with each attempt accompanied by a strange grinding noise, or when your clutch keeps grabbing harshly rather than engaging smoothly during a shift, you might be in need of a new flywheel. At the beginning of these signs of failure, any driver may think that something else is wrong. Some may think there's an issue with the starter solenoid not being able to turn the ring gear. Others may think that they need a new clutch friction disc. But without performing a few good inspections, it is impossible to tell if you actually need to replace your flywheel or not. First, one should watch the starter try to engage the ring gear. It can be turned manually as well so that all the teeth can be inspected. If all that checks out, then the next step should be to open up the bell housing to reveal the clutch kit. It can be removed from the flywheel so that the surface can be inspected. Sometimes, it just needs to be resurfaced. But if it is very old, then it will likely need to be replaced.
Your engine's four-stroke cycle produces power through the combustion of the air-fuel mixture inside the cylinder head. This power turns the crankshaft inside the engine block. Bolted to the rear of the crankshaft is your flywheel, and it is responsible for transferring the engine's torque to the transmission via the clutch. Additionally, your flywheel has a ring gear around its perimeter that your starter motor uses to turn the crank when the engine starts. Before this, drivers manually cranked their engine to get it to turn over. So, as you can see, this part serves multiple purposes and your car will cease to operate properly if it is broken.
Changing your flywheel is a task that will likely take most of the day... even for an experienced mechanic with the right tools. All cars are different, but the main steps are all about the same.