National 7412S Manual Transmission Input Shaft Seal

Manual Transmission Input Shaft Seal for GM and Ford Applications

The National 7412S manual transmission input shaft seal is built for vehicles that need a precise seal at the transmission input shaft. It uses nitrile material, a clockwise-spiral lip design, and Redicoat protection to help maintain sealing performance in demanding manual transmission service.

With a 1.250-inch shaft size, 1.754-inch outside diameter, and 0.250-inch width, this National oil seal is a direct-fit option for a wide range of classic and late-model performance and truck applications, including Chevrolet Camaro, Corvette, Ford Mustang, and Dodge Viper platforms.

Key Features

• Part number: 7412S
• Manual transmission input shaft seal / oil seal
• Nitrile construction for sealing durability
• Clockwise-spiral lip design
• Redicoat: Yes
• Inside diameter: 1.250 in. (31.750 mm)
• Outside diameter: 1.754 in. (44.550 mm)
• Width: 0.250 in. (6.350 mm)
• Housing bore: 1.750 in. (44.450 mm)
• National 7000 series, Type 48

Detailed Description

National has supplied sealing products for more than 75 years, and the 7412S reflects that focus on fit and function. This manual transmission input shaft seal is engineered for applications that require a stable seal around the input shaft to help keep transmission fluid where it belongs. The nitrile sealing material and spiral lip profile are suited to manual gearbox service, while the Redicoat finish supports installation and sealing consistency.

Fits 2013-2019 Cadillac ATS, 2010-2019 Chevrolet Camaro, 2004-2019 Chevrolet Corvette, 2009-2019 Dodge Challenger, and 1996-2019 Ford Mustang. It also fits many additional applications including Chevrolet SS, Dodge Viper, Pontiac G8, Cadillac CTS, and select Tremec, Borg-Warner, GMC Saginaw, and New Process transmission combinations listed in the fitment data. This part cross-references Gates 12355 and 12363 for the same application.

What It Helps Address

• Transmission fluid seepage at the input shaft
• Oil leakage around the manual transmission front seal area
• Seal wear from age, heat, and mileage
• Service issues on manual transmissions with the specified shaft and bore dimensions
• Leak-related contamination around the bellhousing area

Installation Notes and Tips

Verify shaft diameter, housing bore, and transmission type before installation. This seal is specified for a 1.250-inch shaft and 1.750-inch housing bore, so matching the transmission model and configuration is important. Clean the bore and shaft surface thoroughly, inspect for scoring or wear, and install the seal squarely to avoid distortion of the lip.

For fitment-specific applications, confirm the transmission family noted in the vehicle listing, such as Tremec T56, Tremec T5WC, Borg-Warner T5WC, Borg-Warner T18, or GMC Saginaw variants where shown.

Quality Assurance

National builds sealing solutions with long-term industry experience and ongoing design support for modern and legacy vehicles. The 7412S is part of the National 7000 series and is produced to meet the dimensional and material requirements listed above.