GM Duramax Damper/Harmonic Balancer. GM Original Equipment Engine Harmonic Balancer is a direct replacement for your vehicle’s original component. It is connected to the crankshaft of your vehicle’s engine to help reduce torsional vibration and serves as a pulley for the engine accessory drive belts. This original equipment engine harmonic balancer has been manufactured to fit your specific GM vehicle, providing the same performance, durability, and service life you expect from General Motors.