The rotating assembly in Duramax engines includes the crankshaft, connecting rods, pistons, and flywheel. It converts linear piston motion into rotational torque. Forged steel crankshafts provide strength under extreme load. Connecting rods transmit combustion force to the crankshaft. Pistons endure high heat and pressure within the cylinders. The flywheel stabilizes rotation and stores kinetic energy. Balanced components reduce vibration and improve engine efficiency.