A4. S4; 4 Cylinder; Auto Trans. S4; 4 Cylinder; Manual Trans; 6 Speed. S4; 6 Cylinder; Auto Trans. S4; 6 Cylinder; Manual Trans; 6 Speed. A single complete drive axle assembly, used on vehicles that utilize dependent suspension systems, that includes a differential and drive axles to deliver power to the wheels of a vehicle in order to drive the vehicle. Device connecting Drive Shaft to Axle Shafts that allows for varied speeds of wheel rotation.