Axles. The front and rear axles, including suspension assemblies, shall have a gross axle weight rating at least equal to that portion of the load as would be imposed by the chassis manufacturer's maximum gross vehicle weight rating. The rear axle shall be of the full-floating type. The rear suspension assembly shall have a gross weight rating at ground equal to or exceeding that portion of the total load as would be imposed by the manufacturer's maximum gross vehicle weight rating. Air Cleaner. The engine intake air cleaner shall be furnished and properly installed by the chassis manufacturer to meet engine specifications. Heater Outlets. The chassis engine shall provide inlet and outlet holes in which heavy duty cut-off valves shall be installed in accessible locations for attachment of the bus heating system water lines. Oil Filter. An engine mounted filter shall be provided by the engine manufacturer. Transmission. A transmission shall have a minimum of four forward speeds and one reverse speed. Drive Shaft. Each segment of the drive shaft shall be equipped with a suitable guard to control its motion and prevent accident or injury in the event of its fracture or disconnection.