This brake disc is the component that the parking-brake mechanism clamps against to hold the tractor stationary when the lever is engaged. It is splined to the transmission output shaft and sits inside the brake housing. When the parking brake is applied, the actuating linkage presses friction pads against both faces of the disc, locking the driveline. A worn disc reduces clamping force, allowing the tractor to creep on a slope. The disc is manufactured to the original spline profile and thickness specification so that it engages the shaft without play and maintains the correct clearance for the actuating mechanism. On installation, ensure the friction surfaces are clean and free of oil.