This shaft transfers rotary motion from the front of the straw-walker assembly to the rear, driving the walker cranks that separate grain from the straw mat. It can be installed at either the front or the rear position; when mounted at the rear, the longer end of the shaft accommodates the pulley that drives downstream components. The shaft rotates within bushings that must be in good condition to prevent excessive play and vibration. A worn bushing or misaligned shaft causes uneven walker timing, reducing separation efficiency and increasing grain loss over the sieves. On reinstallation, ensure the bushings are free of debris and that the shaft rotates freely before securing the pulley.