National 710721 Automatic Transmission Extension Housing Seal

Automatic Transmission Extension Housing Seal

National 710721 is an automatic transmission extension housing seal built for specific Honda and Acura applications with a Borg-Warner ITM-II transfer case. It uses a polyacrylate sealing material and a bi-directional lip design to help maintain a secure seal at the transmission extension housing. This National 710721 oil seal is sized for metric applications and matches the shaft and housing dimensions listed below.

Key Features

• Automatic transmission extension housing seal for select Honda and Acura vehicles
• Polyacrylate sealing material for transmission sealing applications
• Bi-directional lip design
• Metric dimensions: 38.000 mm shaft / 62.000 mm housing bore
• Outside diameter: 62.200 mm; width: 9.000 mm
• Part description: oil seal
• National 710721 part number for direct reference

Detailed Description

National 710721 is an extension housing oil seal engineered for transmission sealing service where the shaft measures 1.496 inches (38.000 mm) and the housing bore measures 2.441 inches (62.000 mm). The seal’s 2.449-inch (62.200 mm) outside diameter and 0.354-inch (9.000 mm) width support a precise metric fit in the extension housing area. National has focused on sealing solutions for decades, and this part reflects that experience with a polyacrylate construction and a bi-directional lip profile. This part cross-references Remy 14921 for the same application.

Compatible With 2001-2015 Acura MDX, 2003-2017 Honda Pilot, 2006-2014 Honda Ridgeline, 2007-2018 Acura RDX, and 2010-2011 Honda Accord Crosstour in full-time 4WD applications with the Borg-Warner ITM-II transfer case and 1-speed configuration. It also fits 2012-2015 Honda Crosstour and 2001-2002 Acura MDX in the listed applications. Use National 710721 when replacing a worn transmission extension housing seal on these Acura MDX, Honda Pilot, and Honda Ridgeline platforms.

What It Helps Address

• Transmission fluid seepage at the extension housing
• Leakage around the output shaft seal area
• Seal wear from age, heat, and fluid exposure
• Loss of sealing performance in full-time 4WD transfer case applications
• Service replacement for a damaged or hardened oil seal

Installation Notes and Tips

Verify shaft diameter, housing bore, and seal width before installation. Clean the housing bore and shaft surface thoroughly, and inspect for scoring, corrosion, or burrs that can affect sealing. Confirm the vehicle’s transfer case and drivetrain configuration against the fitment notes before ordering. National 710721 should be installed only in applications matching the listed dimensions and vehicle coverage.

Quality Assurance

National has built a long-standing reputation in sealing technology and continues to supply premium sealing solutions for modern vehicles. The 710721 seal is part of the 710700 series and is manufactured to meet the dimensional and material requirements listed for the application.