National 7412S Manual Transmission Input Shaft Seal

Reliable Manual Transmission Input Shaft Seal for Multiple Vehicles

The National 7412S manual transmission input shaft seal is engineered to provide durable sealing performance for a wide range of vehicles including Ford, Chevrolet, Jeep, and Nissan models. Constructed from nitrile material with a clockwise-spiral lip design, this oil seal helps maintain transmission integrity by preventing fluid leaks and contamination.

• Material: High-quality nitrile for resistance to oil and wear
• Inside Diameter: 1.250 inches (31.750 mm)
• Outside Diameter: 1.754 inches (44.550 mm)
• Thickness/Width: 0.250 inches (6.350 mm)
• Helix Type: Clockwise-spiral lip design for effective sealing
• Housing Bore: 1.750 inches (44.450 mm)
• Redicoat finish for enhanced durability
• Part Number: 7412S, Series 7000

Detailed Description of the National 7412S Input Shaft Seal

This manual transmission input shaft seal is designed to fit a variety of makes and models, including popular vehicles such as the Ford Bronco, Chevrolet Camaro, Jeep Cherokee, and Nissan 280ZX. The seal’s nitrile construction offers excellent resistance to petroleum-based fluids and high temperatures commonly found in transmission systems. The clockwise-spiral lip design ensures a tight seal around the input shaft, reducing the risk of oil leaks and contamination that can lead to premature transmission wear.

The 7412S features precise dimensions with an inside diameter of 1.250 inches and an outside diameter of 1.754 inches, making it compatible with housing bores measuring 1.750 inches. Its 0.250-inch thickness provides a robust barrier against fluid escape while maintaining flexibility for proper shaft movement. The Redicoat finish adds an extra layer of protection against corrosion and wear, extending the service life of the seal.

Applications and Common Issues Addressed

• Prevents manual transmission fluid leaks on vehicles like the Chevrolet Blazer and Ford F-150
• Protects input shaft bearings from contamination in Jeep CJ7 and Nissan 300ZX transmissions
• Reduces risk of transmission overheating caused by fluid loss in Dodge Ram 1500 and Cadillac CTS
• Maintains proper lubrication levels in Pontiac Firebird and Buick Century manual transmissions
• Helps avoid costly transmission repairs due to seal failure in GMC Sierra and Mercury Cougar

Installation Notes and Tips

When installing the National 7412S input shaft seal, ensure the transmission housing bore is clean and free of debris. Use appropriate tools to press the seal evenly into place without damaging the sealing lip. Verify the seal orientation matches the clockwise-spiral lip design to optimize sealing performance. It is recommended to inspect the input shaft for wear or damage before installation to ensure a proper fit and long-lasting seal.

Quality Assurance and Warranty

National manufactures the 7412S input shaft seal to meet industry standards for durability and performance. The use of nitrile material and Redicoat finish reflects a focus on resistance to oil, heat, and corrosion. While specific warranty details are not provided, National’s reputation in transmission sealing systems supports reliable product quality for professional and DIY automotive repairs.