National 5778 Differential Pinion Seal - Front Outer or Rear Outer

National 5778 Differential Pinion Seal

National 5778 is a differential pinion seal built for driveline sealing at the pinion shaft. It uses polyacrylate material with Redicoat protection and measures 1.552 in. inside diameter, 3.165 in. outside diameter, and 0.645 in. thickness for a precise OE-style service replacement.

National has supplied sealing solutions for more than 75 years, and this oil seal reflects that focus on dimensional accuracy and modern vehicle coverage. It is a direct-fit option for many Jeep, Ford, Dodge, Chevrolet, GMC, Honda, and Isuzu applications that use the listed axle and ring gear configurations.

Key Features

• Part number 5778 differential pinion seal
• Polyacrylate construction for sealing performance
• Redicoat surface treatment
• Inside diameter: 1.552 in. / 39.420 mm
• Outside diameter: 3.165 in. / 80.390 mm
• Thickness: 0.645 in. / 16.383 mm
• Housing bore: 3.160 in. / 80.260 mm
• Series 5000, Type 72 oil seal

Detailed Description

National 5778 is a differential pinion seal for driveline and axle service where the pinion shaft must retain gear oil and keep contaminants out of the housing. The seal’s 1.552-inch shaft diameter, 3.165-inch outside diameter, and 0.645-inch width make it a dimension-specific replacement for many front outer and rear outer applications. This part cross-references Monroe Shocks & Struts 5778 for the same application.

Compatible vehicle coverage includes long-tail search applications such as 1994-2003 Dodge Ram 1500 front outer differential pinion seal, 1997-2001 Jeep TJ rear outer pinion seal, and 1980-1996 Ford F-150 front outer axle seal service. It also appears in Jeep Wrangler, Cherokee, Grand Cherokee, Bronco, F-250, and Corvette driveline repair listings where the axle and ring gear specifications match.

What It Helps Fix

• Gear oil leaking from the differential pinion area
• Contamination entering the axle housing through a worn seal
• Wet pinion yoke or driveline residue around the axle nose
• Seal wear caused by age, heat, or mileage
• Service issues on front outer or rear outer differential applications

Installation Notes and Tips

• Verify shaft, housing bore, and width dimensions before installation.
• Confirm axle type, ring gear size, and position against the vehicle listing.
• Inspect the pinion yoke and sealing surface for wear or scoring before assembly.
• Clean the housing bore and surrounding area so the seal seats evenly.
• Use the exact application notes for Jeep, Ford, Dodge, Chevrolet, GMC, Honda, and Isuzu fitment.

Quality Assurance

National builds sealing products with more than 75 years of industry experience and ongoing design support for current vehicle requirements. Part number 5778 is engineered as a precision oil seal for differential service and is backed by National’s established sealing expertise.