National 6638S Wheel Seal - Front Inner

National 6638S Wheel Seal Overview

National 6638S is a wheel seal built for driveline and axle sealing applications where the shaft and housing dimensions must match precisely. It uses nitrile material and Redicoat protection to support a reliable seal at the wheel end, helping maintain proper lubrication and keep contaminants out.

Compatible With Ford and other vehicle applications that use the same dimensions, this National wheel seal is identified by part number 6638S and is part of National’s 6000 series. It is an oil seal with a 3.500 inch shaft diameter, 4.848 inch outside diameter, and 0.875 inch width.

Key Features

• National wheel seal, part number 6638S
• Nitrile sealing material for common axle and wheel-end service needs
• Redicoat surface treatment
• 3.500 inch inside diameter / shaft size
• 4.848 inch outside diameter for a 4.841 inch housing bore
• 0.875 inch width for dimensional match-up
• 6000 series oil seal design

Product Details

National 6638S is engineered as a wheel seal for applications that require accurate shaft, bore, and width dimensions. The seal measures 88.900 mm inside diameter, 123.140 mm outside diameter, and 22.230 mm width, making it a direct dimensional reference for service work. National has supplied sealing solutions for decades, and this seal reflects that focus on fit and material selection.

This part cross-references FEL-PRO 35062 for the same application. For buyers searching Ford wheel seal replacement, rear axle seal service, or National 6638S fitment, dimensional verification remains the key step before installation.

Common Problems This Seal Helps Address

• Gear oil leakage at the wheel end
• Contamination entering the axle or hub area
• Seal wear from age, heat, or mileage
• Loss of lubrication caused by a damaged sealing lip
• Service issues tied to incorrect shaft or housing dimensions

Installation Notes and Tips

Confirm the shaft diameter, housing bore, and seal width before installation. Inspect the sealing surface for grooves, corrosion, or debris, and clean the bore thoroughly so the seal seats evenly. Use proper installation tools to avoid distorting the nitrile sealing lip or damaging the Redicoat surface.

For Ford wheel seal replacement jobs and other axle service applications, verify the original part dimensions against National 6638S before assembly. The part number 6638S should be matched to the vehicle’s required seal measurements, not just the model name.

Quality Assurance

National has a long history in sealing technology and continues to develop sealing solutions for modern vehicles. The 6638S wheel seal is built to the listed dimensional specifications and material details for consistent service replacement.