National 6818 Differential Pinion Seal - Front Outer or Rear Outer

National 6818 Differential Pinion Seal

National 6818 is a differential pinion seal built for rear axle sealing applications that require a precise shaft and housing fit. It uses nitrile material and measures 1.739 in. inside diameter, 3.008 in. outside diameter, and 0.500 in. width for a direct-fit service replacement in supported driveline applications.

Compatible With Chevrolet Bel Air, Impala, El Camino, Corvette, Pontiac Laurentian, and GMC G1000 Series rear outer differential positions, this seal is specified for vehicles using the listed axle and ring gear configurations. National 6818 is also cross-referenced to Gates 6818 for the same application.

Key Features

• Part number: 6818
• Part type: differential pinion seal / oil seal
• Material: nitrile for sealing performance in driveline service
• Inside diameter: 1.739 in. (44.170 mm)
• Outside diameter: 3.008 in. (76.400 mm)
• Width: 0.500 in. (12.700 mm)
• Housing bore: 3.000 in. (76.200 mm)
• Series: 6000, Type 71

Detailed Description

National 6818 is an OE-style differential pinion seal designed for rear outer axle sealing where the shaft and housing dimensions must match closely. The nitrile construction and listed dimensions support a proper seal interface in driveline and axle service, including Chevrolet Bel Air, Chevrolet Impala, Chevrolet El Camino, Chevrolet Corvette, Pontiac Laurentian, and GMC G1000 Series applications shown in the fitment data. Use the part number 6818 when matching replacement seals by size and application.

What It Helps Address

• Gear oil seepage at the differential pinion area
• Seal wear from age, heat, and driveline contamination
• Leaks caused by a damaged or hardened original seal
• Service replacement needs on rear outer axle assemblies
• Fitment matching for Chevrolet and GMC rear differential applications

Installation Notes and Tips

Verify shaft diameter, housing bore, and seal width before installation. Confirm the rear outer position and the axle or ring gear notes listed for your vehicle, especially on Chevrolet Bel Air, Impala, El Camino, Corvette, and Pontiac Laurentian applications. Inspect the sealing surface for scoring or wear before installing National 6818, and make sure the bore is clean and free of debris.

Quality Assurance

National has supplied sealing solutions for more than 75 years and continues to develop replacement parts for modern and legacy vehicles. The 6818 seal reflects that focus on dimensional accuracy and driveline sealing performance.