A HGV flywheel is a heavy, circular metal disc that is located between the engine and the transmission in heavy goods vehicles (HGV). The flywheel's main function is to act as a mechanical buffer between the engine and transmission, smoothing out the engine's power pulses and providing a consistent rotational force to the transmission. It is also used as a mounting surface for the clutch, which allows the driver to engage and disengage the engine from the transmission. The flywheel is typically made of cast iron or steel, and is designed to withstand the high torque and temperature of the HGV engine. It is important to regularly check and maintain your flywheel as a worn or damaged flywheel can cause clutch and transmission issues.