The rotating assembly in the 6.6L LB7 Duramax (2001–2004) includes the crankshaft, connecting rods, pistons, and flywheel or flex plate—components that convert combustion energy into rotational motion to drive the vehicle. It forms the core of the engine’s bottom end and is built to handle the high torque and cylinder pressure typical of diesel performance. The crankshaft is forged steel, strong and durable, turning the pistons’ linear motion into rotation. The connecting rods link the pistons to the crankshaft and are designed for heavy-duty operation. The cast-aluminum pistons handle high compression but can be a weak point in high-performance setups, where forged upgrades are often used. The flex plate connects the crankshaft to the torque converter in automatic transmission models, transferring power to the drivetrain.