The Ford 1C3Z-3B396-CB is a genuine OEM 4WD front automatic/manual locking hub assembly engineered for 1999–2004 Ford Super Duty trucks and 2000–2005 Ford Excursions equipped with Electronic Shift-on-the-Fly (ESOF). Manufactured to exact factory Motorcraft specifications, this 30-spline hub features an integrated dual-function engagement mechanism with an internal vacuum-actuated diaphragm and a manual override dial (Auto/Lock). Ford constructs the internal drive clutch with precision-machined splines and factory-grade environmental seals to withstand demanding front axle loads and maintain reliable connection to the outer axle shaft.

Non-functioning 4WD when switching the dash selector switch, loss of automatic front hub engagement, stripped plastic internal ratchet gears, seized manual override dials, and vacuum leaks causing HVAC blend doors to default airflow to the defrost vents are what this hub fixes. On 1999–2004 Super Duty platforms, factory ESOF locking hubs rely on delicate internal vacuum seals and plastic engagement cams that dry out, crack, or become fouled by water, mud, and road salt intrusion. When the internal diaphragm tears or the plastic cams strip, the vacuum pulse from the ESOF solenoid cannot pull the drive gear into the axle splines, leaving the front wheels disengaged. Replacing a seized or leaking hub with a genuine Ford OEM unit restores hands-free automatic 4x4 shifting from the cab while maintaining a manual "Lock" option for severe off-road conditions. It is sold as a single front locking hub assembly; two hubs are required to service an entire front axle, and outer retaining snap rings, wheel unit bearings, and vacuum knuckle seals are sold separately.

It fits 30-spline Dana 50 and Dana 60 front drive axles on 1999–2004 Ford Super Duty F-250 and F-350 single-rear-wheel (SRW) trucks and 2000–2005 Ford Excursions equipped with the factory ESOF pulse-vacuum 4WD system.

Fitment

• 1999–2003 Ford F-250 Super Duty 4WD 7.3L Powerstroke (ESOF Auto/Lock)
• 2003–2004 Ford F-250 Super Duty 4WD 6.0L Powerstroke (ESOF Auto/Lock)
• 1999–2003 Ford F-350 Super Duty 4WD SRW 7.3L Powerstroke (ESOF Auto/Lock)
• 2003–2004 Ford F-350 Super Duty 4WD SRW 6.0L Powerstroke (ESOF Auto/Lock)
• 2000–2005 Ford Excursion 4WD 7.3L & 6.0L Powerstroke (ESOF Auto/Lock)
• 1999–2004 Ford F-250 / F-350 Super Duty 4WD Triton Gas (5.4L V8 & 6.8L V10)
• Genuine OEM Ford Motorcraft replacement part
• Direct replacement for factory part numbers 1C3Z-3B396-CB, 1C3Z-3B396-AA, and 600-203
• Features factory dual-mode operation: vacuum-actuated "Auto" and manual "Lock"
• Precision 30-spline internal drive gear for Dana 50 and Dana 60 front axles
• Single front locking hub assembly only (two required per vehicle)

Park the truck on a level surface, engage the parking brake, and remove the front wheel center cap to expose the hub bore. Using external snap-ring pliers, compress and remove the large wire retaining ring seated inside the internal groove of the wheel unit bearing, then slide the old locking hub straight out of the bore. Clean all old, hardened grease, grit, and corrosion out of the unit bearing splines and the outer axle shaft stub splines using brake cleaner and a wire brush. Lightly coat the splines with a thin film of clean chassis grease—never pack the locking hub cavity with heavy wheel bearing grease, as excessive grease will hydraulically lock the vacuum diaphragm and prevent the internal clutch from sliding into engagement during cold weather. Inspect the large perimeter sealing O-ring and apply a light wipe of clean silicone grease to ensure an airtight seal against the hub bore. Slide the new Ford hub assembly squarely into the unit bearing, verify the splines mesh smoothly, reinstall the large retaining snap ring into its machined groove until fully seated, and cycle the manual dial between "Auto" and "Lock" to confirm free mechanical movement.