National 4934 Automatic Transmission Extension Housing Seal

Automatic Transmission Extension Housing Seal

National 4934 is an automatic transmission extension housing seal built for vehicles that need a precise seal at the transmission tail housing. It uses a polyacrylate sealing material, a counter-clockwise spiral lip design, and Redicoat treatment to support consistent sealing performance in demanding driveline applications.

With dimensions that match the application closely, this seal is used on a wide range of GM trucks, vans, SUVs, and performance models, including Chevrolet Silverado 1500, GMC Sierra 1500, and Chevrolet Express 1500 applications. National 4934 is a direct-fit service part for extension housing sealing on many 4L60-E, 4L65-E, 4L70-E, and 4L85-E automatic transmission setups.

Key Features

• Automatic transmission extension housing seal for rear output sealing
• Polyacrylate sealing material for transmission fluid resistance
• Counter-clockwise spiral lip design for sealing support
• Redicoat treated surface
• Inside diameter: 1.503 in. / 38.180 mm
• Outside diameter: 2.379 in. / 60.430 mm
• Housing bore: 2.374 in. / 60.300 mm
• Thickness: 0.374 in. / 9.500 mm
• Flanged outside diameter: 2.723 in. / 69.164 mm

Product Details

National 4934 is an oil seal for the transmission extension housing, where accurate shaft sealing is critical to keeping fluid contained at the rear of the transmission. National has supplied sealing solutions for more than 75 years, and this part reflects that focus with application-specific dimensions and a material choice suited to transmission service. This part cross-references ATP CO-36 and SKF 15133 for the same application.

What This Seal Helps Address

• Transmission fluid seepage at the extension housing
• Leakage around the output shaft area
• Wear-related sealing loss at the rear of the transmission
• Service replacement for damaged or hardened original seals
• Maintenance on GM 4L60-E, 4L65-E, 4L70-E, and 4L85-E transmission applications

Installation Notes and Tips

Confirm shaft, housing bore, and seal dimensions before installation. Clean the extension housing bore thoroughly, inspect the output shaft surface for scoring, and install the seal squarely to avoid lip damage. This part is listed across many fitments, including 1996-2014 Chevrolet Express 1500, 1999-2008 GMC Sierra 1500, and 2009-2013 Chevrolet Silverado 1500 applications, so transmission type and configuration should be verified against the vehicle build.

Quality Assurance

National builds sealing products with long-term industry experience and ongoing design support for modern vehicles. Part number 4934 is manufactured as a precision transmission seal for service replacement use.