This flywheel ring gear is the toothed ring pressed onto the outer diameter of the engine flywheel. It engages with the starter motor pinion to crank the engine during startup. The ring gear is a wear item; a worn or chipped tooth set prevents the starter from engaging properly, resulting in a no-start condition or grinding noise. This replacement ring gear is manufactured to match the original tooth profile and press-fit dimensions, so it seats correctly on the flywheel without additional machining. During installation, the old ring gear must be removed by cutting or splitting, and the new ring gear should be heated evenly before pressing it onto the flywheel to achieve the correct interference fit.