National 100086 Automatic Transmission Extension Housing Seal

Automatic Transmission Extension Housing Seal for Ford 4R100

National 100086 is an automatic transmission extension housing seal built for Ford applications using the 4R100 transmission and a 1.880-inch shaft. It uses a fluoro-elastomer sealing material and a counter-clockwise spiral lip design to support consistent sealing at the extension housing. This National 100086 seal is a direct-fit service part for select Ford, Lincoln, and Mercury-era truck and van platforms listed below.

Key Features

• Automatic transmission extension housing seal / oil seal
• 1.880-inch inside diameter and shaft size
• Fluoro-elastomer construction for sealing durability
• Counter-clockwise spiral lip design
• Redi-Coat surface treatment
• National Series 100000 design
• Part number: 100086

Product Details

National 100086 is engineered around the dimensions required for the transmission extension housing on Ford 4R100-equipped vehicles. The seal measures 1.880 inches inside diameter, 3.176 inches outside diameter, and 0.480 inch thickness, with a flanged outside diameter of 3.500 inches. Its housing bore is 3.169 inches, and the overall width with side lip is 1.310 inches. The fluoro-elastomer material and spiral lip profile are selected to maintain a stable seal at the extension housing where transmission fluid retention is critical. This part cross-references Gates 18725 for the same application.

Vehicle Fitment

• Fits 2003-2005 Ford E-150, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 2003-2005 Ford E-150 Club Wagon, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 2003-2005 Ford E-250, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 2003-2005 Ford E-350 Club Wagon, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 2001-2005 Ford E-350 Super Duty, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 1999 Ford E-350 Super Duty, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 2000-2005 Ford Excursion, N/A — 1.880-inch shaft.
• Fits 1999-2005 Ford Expedition, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 1999-2005 Ford F-150, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 2004 Ford F-150 Heritage, N/A — 1.880-inch shaft.
• Fits 1999-2004 Ford F-250 Super Duty, N/A — 1.880-inch shaft.
• Fits 1999-2004 Ford F-350 Super Duty, N/A — 1.880-inch shaft.
• Fits 1998-2004 Lincoln Navigator, N/A — 1.880-inch shaft.
• Fits 2000-2002 Ford E-150 Econoline, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 2000-2002 Ford E-150 Econoline Club Wagon, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 1999-2002 Ford E-250 Econoline, N/A — 1.880-inch shaft.
• Fits 1999-2002 Ford E-350 Econoline Club Wagon, N/A — 1.880-inch shaft.
• Fits 2002 Lincoln Blackwood, N/A — 1.880-inch shaft.
• Fits 1999-2000 Ford E-350 Econoline, N/A — Ford 4R100 transmission with 1.880-inch shaft.
• Fits 1999 Ford F-250, N/A — 1.880-inch shaft.

Common Problems This Seal Addresses

• Transmission fluid seepage at the extension housing
• Leakage around the output shaft area
• Seal wear from heat and fluid exposure
• Loss of sealing performance on 4R100-equipped Ford trucks and vans
• Service replacement for a worn or hardened extension housing seal

Installation Notes and Tips

Verify the shaft diameter, housing bore, and transmission application before installation. Clean the extension housing and shaft sealing surface thoroughly, and inspect for scoring, corrosion, or debris that could affect seal life. Confirm the seal orientation matches the transmission design and install carefully to avoid lip damage during assembly.

Quality Assurance

National has supplied sealing products for more than 75 years and continues to develop sealing solutions for modern vehicle service needs. Part number 100086 is built to the dimensional and material requirements listed above for Ford 4R100 applications.