National 415988 Automatic Transmission Extension Housing Seal

Automatic Transmission Extension Housing Seal

National 415988 is an automatic transmission extension housing seal built for specific heavy-duty GM truck and SUV applications. It uses nitrile material, a Redi-Coat surface, and OE-style dimensions to help maintain a reliable seal at the transmission extension housing.

Compatible With Chevrolet Silverado 2500 HD, Silverado 3500 HD, Silverado 3500 Classic, GMC Sierra 2500 HD, Sierra 3500 HD, Sierra 2500 HD Classic, Sierra 3500 Classic, Sierra 3500, and Hummer H1 applications listed below.

• Part number: 415988
• Part type: automatic transmission extension housing seal / oil seal
• Material: nitrile
• Redi-Coat: yes
• Inside diameter: 2.562 in. / 65.070 mm
• Outside diameter: 3.628 in. / 92.150 mm
• Thickness/width: 0.375 in. / 9.530 mm
• Housing bore: 3.623 in. / 92.020 mm
• Series: 410000
• Zero duplication part

Fitment Details

• Fits 2003-2019 Chevrolet Silverado 2500 HD, N/A
• Fits 2007-2019 Chevrolet Silverado 3500 HD, N/A
• Fits 2004-2019 GMC Sierra 2500 HD, N/A
• Fits 2007-2019 GMC Sierra 3500 HD, N/A
• Fits 2007 Chevrolet Silverado 3500 Classic, N/A
• Fits 2007 GMC Sierra 2500 HD Classic, N/A
• Fits 2007 GMC Sierra 3500 Classic, N/A
• Fits 2004-2006 Chevrolet Silverado 3500, N/A
• Fits 2004-2006 GMC Sierra 3500, N/A
• Fits 2006 Hummer H1, N/A
• Fits 2001-2003 Chevrolet Silverado 3500, N/A with Allison 1000 Transmission
• Fits 2001-2003 GMC Sierra 2500 HD, N/A with Allison 1000 Transmission
• Fits 2001-2003 GMC Sierra 3500, N/A with Allison 1000 Transmission
• Fits 2001-2002 Chevrolet Silverado 2500 HD, N/A with Allison 1000 Transmission

What This Seal Helps Address

• Transmission fluid seepage at the extension housing
• Leakage around the output shaft area
• Seal wear from age, heat, and fluid exposure
• Service replacement for GM heavy-duty truck and Hummer H1 transmission repairs

Installation Notes and Tips

Verify the housing bore, shaft diameter, and seal dimensions before installation. Clean the extension housing and shaft sealing surface thoroughly, and inspect for scoring or wear that could affect sealing performance. This part cross-references SKF 25661 for the same application.

Quality Assurance

National has supplied sealing products for more than 75 years and continues to develop sealing solutions for modern vehicles. Part number 415988 is built to National’s dimensional standards for the listed Chevrolet, GMC, and Hummer applications.