National 6638S Wheel Seal - Front Inner

National 6638S Wheel Seal Overview

The National 6638S wheel seal is engineered to provide reliable sealing performance for driveline and axle applications. Designed with precision, this oil seal helps maintain proper lubrication and prevents contaminants from entering the wheel hub assembly.

• Inside diameter: 3.500 inches (88.900 mm)
• Outside diameter: 4.848 inches (123.140 mm)
• Width: 0.875 inches (22.230 mm)
• Material: Durable nitrile compound for resistance to oil and wear
• Redicoat coating for enhanced corrosion protection
• Series: 6000, ensuring compatibility with standard axle housings

Detailed Product Description

The National 6638S wheel seal is constructed from nitrile, a synthetic rubber known for its excellent resistance to petroleum-based oils and greases. This seal features a 3.5-inch (88.9 mm) inside diameter and a 4.848-inch (123.14 mm) outside diameter, making it suitable for axle shafts and housings with matching dimensions. The 0.875-inch (22.23 mm) width provides a secure fit to prevent leakage. Additionally, the Redicoat treatment enhances the seal’s corrosion resistance, extending its service life in harsh environments. This oil seal is part of National's 6000 series, designed for dependable sealing in automotive driveline and axle systems.

Applications and Problem Solving

• Prevents oil leaks from wheel hubs and axle assemblies
• Protects bearings and internal components from dirt and moisture
• Maintains proper lubrication for axle shafts in vehicles such as Ford F-150 and Chevrolet Silverado
• Reduces wear caused by contaminants entering the driveline
• Helps avoid costly repairs related to seal failure and axle damage

Installation Notes and Tips

Ensure the shaft and housing bore are clean and free of debris before installation. Verify that the inside diameter of 3.5 inches and outside diameter of 4.848 inches match the vehicle’s axle specifications. Use appropriate tools to press the seal evenly into the housing bore (4.841 inches / 122.96 mm) without damaging the sealing lip. Avoid twisting or stretching the seal during installation to maintain its integrity.

Quality Assurance and Warranty

National wheel seals are manufactured to meet industry standards for durability and performance. The 6638S part number undergoes rigorous quality control to ensure consistent dimensions and material properties. While specific warranty details are not provided, National products typically come with manufacturer-backed quality assurance to support reliable operation in automotive driveline applications.