Clutch Flywheels

The flywheel has 3 important functions. It stores rotational energy to smooth the engine’s power output, the ring gear on the flywheel’s circumference engages with the starter drive to turn the crankshaft when the ignition key is turned to start, and the face of the flywheel provides the friction surface for the clutch disc and the mounting location for the clutch pressure plate. There are solid flywheels and Dual Mass Flywheels (DMFs). The most common cause for flywheel replacement is excessive wear to the clutch contact surface on the flywheel face. However, DMFs can also fail internally and the ring gear can also become damaged and require ring gear or flywheel replacement. No matter what kind of flywheel problem you’re having you can restore optimal performance with one of our OE quality replacement clutch flywheels or improve it with our performance units.

The flywheel is bolted to the end of the crankshaft and rotates whenever the engine is running. The flywheel’s inertia smooths out the intermittent power pulses created by combustion in the cylinders, effectively providing continuous power output. The clutch disc friction material grips the friction surfaces on the flywheel and pressure plate. It is captured between the flywheel and pressure plate and the splined opening at its center engages with the transmission input shaft splines. For an engine to start the reciprocating assembly must rotate to draw in and compress the air/fuel mixture, which is then ignited by the spark plugs, enabling the engine to run on its own. When the ignition key is turned to START, the starter solenoid energizes the starter motor and engages the starter drive gear with the flywheel ring gear. An overrunning clutch disengages the drive from the ring gear when the engine starts.

Every time the clutch is disengaged and engaged, the clutch disc slows down and speeds up, a process that creates heat and wear, gradually decreasing the thickness of the clutch disc and degrading the surface of the flywheel. This wear can be exhibited as scoring, grooving, hot spots, and heat cracks. Once the pressure plate and clutch disc are removed, in addition to visual inspection for these defects the flywheel should be checked for warpage with a straightedge and feeler gauges. Runout can be brought within specs and the surface finish condition can often be restored by machining the flywheel. However, most vehicle manufacturers specify that only a minimal amount of flywheel material can be removed, which may not be enough to correct runout and finish defects. Some flywheels are stepped and the height relationship between the 2 surface levels must be maintained, necessitating the use of a dedicated flywheel grinder. Because of these refinishing factors, a new replacement flywheel is generally the best course of action.

On some vehicles, replacing a flywheel with excessive runout or unacceptable surface finish is the only option because resurfacing is not recommended by the vehicle manufacturer. This is true of most DMFs. A DMF consists of primary and secondary flywheel masses separated by a damping unit, which absorbs engine vibration and reduces the amount that is transferred to the driveline. A series of springs makes up the damping unit. They were initially developed to reduce noise and vibration and improve shifting operation on diesel engine trucks, but now they are also used on many passenger cars. Along with the inability to resurface these flywheels, the damper mechanism can fail, which is typically indicated by excessive noise and vibration. It is recommended that the DMF be replaced when the clutch is replaced, but if you want a less expensive alternative, we offer flywheel conversion kits. These kits include a solid mass flywheel and clutch engineered to work with this type of flywheel. A flywheel conversion kit may not ultimately function as smoothly and with the minimal vibration of a DMF, but you gain dependability at a more economical price.

If you hear grinding noise when you start your vehicle, the flywheel ring gear may have worn, chipped or broken teeth. Ring gear damage can be caused by long term use that involves frequent start-ups, a starter that is not mounted properly, and on older vehicles, engaging the starter while the engine is running. In some cases, such damage may require flywheel replacement, but the ring gear can be replaced on many flywheels for a substantial parts cost savings. The old ring gear can be heated with a torch and driven off with a hammer and chisel. The new ring gear is then heated so it expands for fitment around the circumference of the flywheel.

No matter what you’re working on, we have the replacement clutch flywheel and components needed to restore proper vehicle operation. We offer clutch flywheels and components that are manufactured to original equipment specifications, so when repairs are completed you can count on the performance your vehicle was designed to deliver. When effecting clutch or starting system repairs, all components should be carefully examined during the process. If you’re replacing the ring gear the starter drive should also be inspected as well as the starter mounting to make sure shims, if required, and any special hardware is in place.

When repairing the clutch, the clutch disc, pressure plate and release bearing should be replaced in addition to resurfacing or replacing the flywheel. The clutch disc friction material wears away and can become cracked, and the springs on sprung hub discs can become fatigued from use and heat. The pressure plate surface wears, and the diaphragm spring can weaken over time from heat and extensive use. The release bearing also deteriorates, particularly on vehicles used in stop-and-go traffic where the clutch pedal is depressed for long periods. Along with flywheels and ring gears, we also offer flywheel bolts, gland nuts, shims, dowels pins, and covers.