The 4x4 or 4WD Auto Locking Hubs are located on the front wheel hubs of your F250, F350, F450, F550 Super Duty, Expedition, Excursion, or Navigator.. These hubs connect to the axle assemblies and control how power is transferred from the axle to the fronts wheels of your truck. If your 4x4 system is not working properly a failing actuator is likely the cause. This actuator is a direct replacement for both the front right (passenger side) and front left (driver side) actuator on your .Fits the following vehicles: F250 1999, 2000, 2001, 2002, 2003, 2004 F350 1999, 2000, 2001, 2002, 2003, 2004 F450 1999, 2000, 2001, 2002, 2003, 2004 F550 1999, 2000, 2001, 2002, 2003, 2004 Excursion 2000, 2001, 2002, 2003, 2004, 2005 Expedition 2001, 2002 Navigator 2001, 2002Replaces part number 1C3Z-3B396-CB and 1C3Z3B396CB This is not a genuine OEM part. This part is manufactured by AA Ignition and comes with a lifetime warranty. The term and other vehicle models are used only to identify the vehicles this 4x4 auto locking hub fits.