This gear drives the elevator chain that moves crop material through the cleaning unit. It is mounted on the straw-walker drive shaft and engages with the mating sprocket to maintain timing between the walker and the cleaning shoe. A worn tooth profile causes chain skip, which leads to uneven material flow and reduced separation efficiency. The manufacturer machines the bore and tooth form to match the original shaft interface, so no shimming or adapter is needed during replacement. On reinstall, ensure the retaining key is in good condition and seated fully.