National 4278 Differential Pinion Seal - Rear Outer

Overview of National 4278 Differential Pinion Seal

The National 4278 differential pinion seal is engineered to provide reliable sealing performance for Ford and Lincoln vehicles. Designed with precision dimensions and durable fluoro-elastomer material, this oil seal helps maintain differential integrity and prevent leaks in various models including the Ford F-150 and Lincoln Navigator.

• Inside diameter: 1.812 inches (46.020 mm)
• Outside diameter: 3.096 inches (78.640 mm)
• Flanged outside diameter: 3.400 inches (86.360 mm)
• Thickness/width: 0.485 inches (12.320 mm)
• Material: Fluoro-elastomer for enhanced chemical and heat resistance
• Redicoat coating for improved durability
• Series: 4000, Type 86

Technical Details and Specifications

The National 4278 differential pinion seal features a precise inside diameter of 1.812 inches (46.020 mm) to fit the shaft snugly, ensuring effective sealing around the pinion shaft. The outside diameter measures 3.096 inches (78.640 mm) with a flanged outside diameter of 3.400 inches (86.360 mm), designed to fit securely within the housing bore of 3.091 inches (78.510 mm). The seal thickness of 0.485 inches (12.320 mm) provides a robust barrier against oil leaks. Constructed from fluoro-elastomer, this seal offers resistance to heat, oil, and other automotive fluids, making it suitable for demanding driveline applications. The Redicoat finish adds an extra layer of protection against corrosion and wear.

Compatible Vehicles and Applications

This differential pinion seal is compatible with a range of Ford and Lincoln models, including but not limited to:

• Ford F-150, F-150 Heritage, F-250, F-250 Super Duty, F-350, F-350 Super Duty
• Ford E-150, E-150 Club Wagon, E-150 Econoline, E-150 Econoline Club Wagon
• Ford Excursion, Expedition, Mark LT, Mustang
• Ford Transit-150, Transit-250, Transit-350, Transit-350 HD
• Lincoln Blackwood, Navigator

Use the National 4278 seal to maintain proper differential function and prevent oil leakage in these specific models.

Common Issues Addressed by the National 4278 Seal

• Prevents differential oil leaks that can cause driveline damage
• Reduces contamination ingress into the differential assembly
• Maintains proper lubrication by sealing the pinion shaft
• Helps avoid costly repairs due to seal failure or wear
• Ensures consistent performance under high temperature and pressure conditions

Installation Notes and Tips

• Ensure the housing bore and shaft are clean and free of debris before installation
• Use appropriate tools to press the seal evenly into the housing bore without distortion
• Verify the seal orientation matches the original to maintain proper sealing function
• Check shaft surface for wear or damage that could compromise the seal
• Apply a light coating of compatible lubricant on the seal lip before installation

Quality Assurance and Warranty

The National 4278 differential pinion seal is manufactured to meet industry standards for durability and performance. Constructed from high-quality fluoro-elastomer material with a Redicoat finish, it is designed to withstand harsh operating environments. While specific warranty details may vary, National products typically come with a limited warranty against defects in material and workmanship. Always consult the product documentation or manufacturer for exact warranty terms.