National 3404 Automatic Transmission Oil Pump Seal - Front

Overview of National 3404 Automatic Transmission Oil Pump Seal

The National 3404 automatic transmission oil pump seal is engineered to provide reliable sealing performance for select Ford, Lincoln, and Mercury vehicles. Designed with durable silicone material and a clockwise-spiral lip design, this oil seal helps maintain transmission fluid integrity and prevent leaks.

• Inside diameter options: 1.996 inch (50.7 mm)
• Outside diameter: 2.751 inch (69.88 mm)
• Flanged outside diameter: 3.020 inch (76.71 mm)
• Thickness: 0.325 inch (8.26 mm)
• Sealing material: Silicone with clockwise-spiral lip design
• Compatible with housing bore diameter of 2.743 inch (69.67 mm)
• Part number: 3404, Series 3000

Technical Details and Material Specifications

This National 3404 oil seal is constructed from high-quality silicone, chosen for its resistance to heat, wear, and transmission fluids. The clockwise-spiral lip design enhances sealing efficiency by maintaining consistent contact with the shaft, which measures 1.996 inches (50.7 mm) in diameter. The seal’s flanged outside diameter of 3.020 inches (76.71 mm) ensures a secure fit within the transmission housing bore of 2.743 inches (69.67 mm). With a thickness of 0.325 inches (8.26 mm), this seal balances durability and flexibility to accommodate dynamic transmission conditions.

Compatible Vehicles and Applications

The National 3404 automatic transmission oil pump seal is compatible with a range of Ford, Lincoln, and Mercury models, including but not limited to:

• Ford F-150, F-250, F-350, Expedition, Explorer, Mustang, Bronco, and E-Series Econoline vans
• Lincoln Town Car, Navigator, Mark LT, Mark VIII, and Blackwood
• Mercury Cougar, Grand Marquis, Marauder, Mountaineer, and Cougar

This part is specifically designed for use in automatic transmission oil pumps, ensuring proper sealing and fluid retention in these vehicles.

Common Issues Addressed by the National 3404 Seal

• Prevents transmission fluid leaks that can cause low fluid levels and transmission damage
• Reduces contamination ingress into the transmission system
• Maintains hydraulic pressure within the automatic transmission oil pump
• Minimizes premature wear of transmission components due to fluid loss
• Helps avoid costly transmission repairs related to seal failure

Installation Notes and Tips

• Ensure the transmission 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’s orientation matches the clockwise-spiral lip design for optimal sealing
• Inspect the shaft for wear or damage that could compromise the seal’s effectiveness
• Consult vehicle-specific service manuals for torque specifications and installation procedures

Quality Assurance and Warranty Information

National’s 3404 automatic transmission oil pump seal is manufactured to meet industry standards for durability and performance. The silicone material and design features provide reliable sealing under typical operating conditions. While specific warranty details may vary, National products generally come with a limited warranty against manufacturing defects. It is recommended to verify warranty coverage with the supplier or manufacturer documentation.