National 370003A Wheel Seal - Rear Inner

National 370003A Wheel Seal Overview

National 370003A is an oil bath wheel seal built for driveline and axle sealing applications where consistent retention and contamination control matter. It uses nitrile material and National’s Dynamic Edge design to help maintain a reliable seal in demanding service conditions.

With a 6.325 inch outside diameter, 6.311 inch housing bore, and 4.765 inch shaft diameter, this seal is specified for precise dimensional matching. It is a direct-fit option for applications such as Ford F-250 and Ford F-350 wheel-end service, and it cross-references SKF 47691, 47693, and 47697 for the same application.

Key Features

• Part number: 370003A
• Wheel seal / oil bath seal for driveline and axle sealing systems
• Nitrile construction for sealing performance in wheel-end service
• Dynamic Edge footnote design
• Outside diameter: 6.325 in. (160.480 mm)
• Housing bore: 6.311 in. (160.300 mm)
• Shaft diameter: 4.765 in. (121.030 mm)
• Width: 1.078 in. (27.380 mm)
• Installation tool reference: RD305

Detailed Description

National 370003A is part of the 370000 series and is engineered as a wheel seal for oil bath hub assemblies. The seal dimensions are tightly defined to support proper housing bore and shaft fitment, which is critical for keeping lubricant in place and helping block road debris, moisture, and other contaminants from entering the wheel-end area. National has focused on sealing solutions for more than 75 years, and this part reflects that experience in a service-ready design for heavy-duty axle applications.

For fitment-based searches, this seal is commonly referenced for Ford F-250 and Ford F-350 wheel-end repair work where the correct housing bore and shaft diameter are required. National 370003A is also a useful search term when comparing OE-style wheel seal replacements by dimension and application.

What This Seal Helps Address

• Oil leakage at the wheel-end seal area
• Contamination entering the hub or axle assembly
• Wear caused by degraded sealing surfaces
• Loss of lubricant in oil bath hub applications
• Service issues tied to incorrect seal dimensions

Installation Notes and Tips

• Verify housing bore, shaft diameter, and width before installation.
• Use the specified installation tool RD305 for proper seating.
• Inspect the hub, spindle, and sealing surface for scoring or corrosion before installing the new seal.
• Confirm the seal orientation matches the wheel-end assembly requirements.
• Clean all mating surfaces thoroughly to support a proper seal.

Quality Assurance

National is a long-established sealing brand with a focus on premium sealing solutions for automotive and heavy-duty applications. The 370003A wheel seal is built to dimensional specifications that support accurate replacement service and dependable wheel-end sealing.