Performance Most 4WD vehicles have locking hubs on the front wheels. When the 4WD is not engaged, the locking hubs disconnect the axle. They spin freely, and the rear wheels of the car do all the work of moving the vehicle. When 4WD is engaged, the locking hubs lock in the front wheels to the front axle allowing them to get torque from the engine. Compatible : This 4WD locking hub fits both right and left front axles for your Ford F250 1999-2004, F350 1999-2004, Ford F450 1999-2004, Ford F550 Super Duty 1999-2004, Ford Excursion 2000-2005, Ford Expedition 2001-2002 and Lincoln Navigator 2001-2002 cars. OEM NUMBER OE part number: 1C3Z-3B396-CB, 1C3Z3B396CB, 600-203, 600203. Install either LH (Side) & RH (Passenger Side) FRONT. Fits 4WD (Four Wheel Drive) Models with Auto Locking Hubs only. Notice: If your vehicle is equipped with locking hubs and the have suffered failure, youll notice that selecting your 4 wheel drive wont send drive power to every wheel. Installation & Severces 1. If replacing automatic locking hubs with manual locking hubs reinstall the axle shaft splined steel washer or needle thrust bearing and the axle retaining ring. 2. Install the Hublock assembly against the wheel hub and rotor. 3. Install the wheel and tire and torque the lug nuts One full year of warranty, any questions, welcome to contact seller, we will respond and provide a solution within 24 hours. Compatible : This 4WD locking hub fits both right and left front axles for your Ford F250 1999-2004, F350 1999-2004, Ford F450 1999-2004, Ford F550 Super Duty 1999-2004, Ford Excursion 2000-2005, Ford Expedition 2001-2002 and Lincoln Navigator 2001-2002 cars.