This shaft transmits drive from the reel’s gearbox to the tine-bar assembly that sweeps crop onto the header auger. It is the mechanical link between the reel-speed variator and the cam track that controls tine angle. A bent or worn shaft causes uneven reel rotation, leading to crop loss at the cutterbar. The shaft is machined to match the original spline and keyway geometry so that no reaming or shimming is required during installation. When reinstalling, ensure the universal-joint yokes are aligned in phase to avoid driveline vibration.