National 4765 Automatic Transmission Extension Housing Seal

Overview of National 4765 Automatic Transmission Extension Housing Seal

The National 4765 automatic transmission extension housing seal is engineered for reliable sealing performance in Ford, Lincoln, and Mercury vehicles. Designed with precision to fit models such as the Ford F-150, Explorer, Mustang, and Lincoln Town Car, this seal helps maintain transmission integrity by preventing fluid leaks.

• Inside diameter options: 1.598 inch (40.590 mm)
• Outside diameter: 2.483 inch (63.070 mm)
• Flanged outside diameter: 2.747 inch (69.770 mm)
• Thickness: 0.350 inch (8.890 mm)
• Material: Durable fluoro-elastomer with counter-clockwise spiral lip design
• Redicoat surface treatment for enhanced wear resistance
• Compatible with housing bore diameter of 2.476 inch (62.890 mm)

Detailed Product Description and Specifications

The National 4765 seal is part of the 4000 series and features a 79-type oil seal construction optimized for automatic transmission extension housings. Its fluoro-elastomer material offers chemical resistance and durability under high temperature and pressure conditions typical in transmission systems. The counter-clockwise spiral lip design improves sealing efficiency by directing fluid away from the shaft, reducing leakage risks. The seal’s flanged outside diameter of 2.747 inches ensures a secure fit within the housing bore of 2.476 inches, while the overall width with side lip measures 1.475 inches (37.465 mm), providing a robust sealing surface.

Compatible Vehicles and Applications

This transmission extension housing seal is compatible with a wide range of Ford, Lincoln, and Mercury models, including but not limited to:

• Ford F-150, F-250, F-350, and Expedition
• Lincoln Town Car, Mark LT, Mark VIII, and LS
• Mercury Mountaineer, Cougar, and Marauder
• Ford Explorer, Mustang, Thunderbird, and Crown Victoria
• Ford E-Series vans such as E-150, E-250, and E-350 in various configurations

Common Issues Addressed by National 4765 Seal

• Prevents automatic transmission fluid leaks at the extension housing
• Reduces contamination ingress into transmission components
• Minimizes wear on transmission shafts by maintaining proper lubrication
• Helps maintain transmission pressure and performance
• Prevents premature seal failure due to heat and chemical exposure

Installation Notes and Tips

• Ensure the housing bore and shaft surfaces are clean and free of debris before installation
• Use appropriate tools to avoid damaging the fluoro-elastomer seal lip during installation
• Verify correct orientation of the counter-clockwise spiral lip to ensure proper sealing direction
• Apply a light coating of transmission fluid to the seal lip to facilitate installation and initial lubrication
• Check for proper fitment with the specific Ford, Lincoln, or Mercury model prior to final assembly

Quality Assurance and Warranty

National 4765 seals are manufactured to meet OEM specifications for durability and performance. The fluoro-elastomer material and Redicoat treatment provide enhanced resistance to heat, chemicals, and wear. This part is backed by National’s quality standards and typically includes a limited warranty against manufacturing defects. For detailed warranty terms, refer to the product documentation or manufacturer guidelines.