This crown washer secures the threshing drive assembly on a self-propelled forage harvester. It sits between the rotating component and the retaining fastener, using its eight internal teeth to lock into the mating shaft and prevent loosening under vibration and torque. A worn or missing washer allows the drive element to shift axially, which can cause misalignment and accelerated wear on the adjacent gear or bearing. The manufacturer machines this washer to the original profile so that the tooth engagement matches the shaft spline depth, maintaining the correct axial preload in the stack. On reinstallation, inspect the washer for deformation and replace it if the teeth show any rounding or cracking.