National 325776 Engine Crankshaft Seal - Rear

Rear Crankshaft Oil Seal for GM Trucks and Vans

National 325776 is a rear engine crankshaft seal built for metric applications that require a precise sealing surface and stable lip contact. It uses a fluoro-elastomer construction and a counter-clockwise spiral lip design to help maintain sealing performance in rear crankshaft positions on select Chevrolet and GMC vehicles.

With a 110.000 mm shaft diameter, 130.300 mm outside diameter, and 10.000 mm width, National 325776 is sized for the rear crankshaft seal location used across a wide range of Chevrolet C2500, GMC K3500, and related heavy-duty platforms. This part number is also referenced as 325776 for direct catalog lookup.

Key Features

• Rear engine crankshaft seal / oil seal
• Fluoro-elastomer material for sealing durability
• Counter-clockwise spiral lip design
• Metric dimensions for accurate housing and shaft fit
• Inside diameter: 110.000 mm (4.331 in.)
• Outside diameter: 130.300 mm (5.130 in.)
• Width: 10.000 mm (0.394 in.)
• National part number 325776

Detailed Description

National 325776 is an engine crankshaft seal for the rear position, engineered for vehicles that use a 110.000 mm shaft and a 130.000 mm housing bore. The fluoro-elastomer sealing material is selected for demanding engine environments, while the counter-clockwise spiral lip design supports controlled oil sealing at the crankshaft interface. This seal is listed in National’s 320000 series and is a metric oil seal application.

Compatible vehicle coverage includes Fits 1991-2000 Chevrolet C2500, Rear; Fits 1991-2000 Chevrolet C3500, Rear; Fits 1996-2000 Chevrolet Express 3500, Rear; Fits 1991-2000 GMC C2500, Rear; Fits 1991-2000 GMC K3500, Rear; and Fits 1996-2000 GMC Savana 3500, Rear. It also fits select Chevrolet and GMC Suburban, P-series, G-series, R-series, and V-series rear applications across the 1991-2000 model years. This part cross-references Walker Exhaust 47864 for the same application.

What This Seal Helps Address

• Rear main engine oil leakage at the crankshaft seal area
• Oil seepage from a worn or hardened crankshaft seal
• Seal failure caused by age, heat, or mileage
• Loss of sealing at the rear crankshaft housing bore
• Service replacement needs on Chevrolet and GMC rear seal applications

Installation Notes and Tips

Verify the shaft diameter, housing bore, and seal width before installation to confirm the correct metric fit. Inspect the crankshaft sealing surface for wear, scoring, or contamination, and clean the housing bore thoroughly before pressing the seal into place. For best results, install the seal squarely and avoid damaging the lip during assembly. Confirm rear-position application on the vehicle before ordering.

Quality Assurance

National has supplied sealing solutions for more than 75 years and continues to develop sealing products for modern vehicle requirements. National 325776 reflects that experience with a metric fluoro-elastomer design intended for consistent engine sealing performance in supported Chevrolet and GMC rear crankshaft applications.