National 231003 Engine Crankshaft Seal - Rear

National 231003 Rear Engine Crankshaft Seal

National 231003 is a rear engine crankshaft seal built for precise sealing performance in a wide range of BMW, Land Rover, Bentley, and Rolls-Royce applications. With a nitrile sealing material and metric dimensions, it is specified for rear crankshaft sealing service where oil control and housing fit are critical.

• Rear engine crankshaft seal / oil seal for select European and domestic applications
• Nitrile material for dependable sealing performance
• Metric sizing: 100.000 mm shaft diameter, 125.000 mm housing bore, 12.000 mm width
• Outside diameter: 125.280 mm; inside diameter: 100.000 mm
• National 231003 and 231003 are referenced for the same application
• Cross-references Edelmann 39135 and Four Seasons 39136 for select applications

Detailed Product Overview

This National oil seal is part of the 230000 series and is engineered around exact dimensional requirements: 3.937 in. inside diameter, 4.932 in. outside diameter, and 0.472 in. width. Those measurements matter when servicing rear crankshaft sealing points on vehicles such as the BMW M3, BMW X5, BMW 760Li, and BMW 540i, where proper housing bore and shaft fit help maintain crankcase sealing integrity. National has supplied sealing solutions for more than 75 years, and this part reflects that focus on application-specific design.

Vehicle Fitment

• Fits 2010-2015 BMW 760Li, Rear
• Fits 2003-2008 BMW 760Li, Rear
• Fits 2008-2013 BMW M3, Rear
• Fits 1996-1999 BMW M3, Rear
• Fits 2006-2010 BMW 550i, Rear
• Fits 2006-2010 BMW 650i, Rear
• Fits 2006-2010 BMW M5, Rear
• Fits 2000-2003 BMW M5, Rear
• Fits 2006-2010 BMW M6, Rear
• Fits 2000-2010 BMW X5, Rear
• Fits 2006-2008 BMW 750i, Rear
• Fits 2006-2008 BMW 750Li, Rear
• Fits 2004-2006 BMW 760i, Rear
• Fits 2004-2005 BMW 545i, Rear
• Fits 2004-2005 BMW 645Ci, Rear
• Fits 2002-2005 BMW 745i, Rear
• Fits 2002-2005 BMW 745Li, Rear
• Fits 2003-2005 Land Rover Range Rover, Rear
• Fits 1997-2003 BMW 540i, Rear
• Fits 1994-1995 BMW 540i, Rear
• Fits 2000-2003 BMW Z8, Rear
• Fits 2002 Rolls-Royce Park Ward, Rear
• Fits 1999-2002 Rolls-Royce Silver Seraph, Rear
• Fits 1999-2001 Bentley Arnage, Rear
• Fits 1997-2001 BMW 740i, Rear
• Fits 1993-1995 BMW 740i, Rear
• Fits 1993-2001 BMW 740iL, Rear
• Fits 1988-2001 BMW 750iL, Rear
• Fits 1998-2000 BMW Z3, Rear
• Fits 1994-1997 BMW 840Ci, Rear
• Fits 1993-1997 BMW 850Ci, Rear
• Fits 1992-1995 BMW 320i, Rear
• Fits 1994-1995 BMW 530i, Rear
• Fits 1994-1995 BMW 850CSi, Rear
• Fits 1991-1992 BMW 850i, Rear
• Fits 1983-1984 Ford Ranger, Rear
• Fits 1982-1984 Mazda B2200, Rear

Common Repair Uses

• Rear crankshaft oil leakage at the engine seal area
• Oil seepage near the transmission bellhousing
• Loss of crankcase sealing at the rear main seal location
• Service replacement for worn or hardened nitrile sealing material
• Restoration work on BMW, Land Rover, Bentley, and Rolls-Royce rear seal applications

Installation Notes and Tips

Confirm shaft diameter, housing bore, and seal width before installation to match the engine specification. Inspect the crankshaft sealing surface for wear, scoring, or contamination, and clean the housing bore thoroughly so the seal seats evenly. For BMW M3, BMW X5, and BMW 760Li rear seal service, verify the rear position and engine application before assembly.

Quality Assurance

National is a long-established sealing brand with more than 75 years of experience in sealing technology. The 231003 is built as a metric oil seal with application-specific dimensions and material selection for rear crankshaft sealing service.