National 4638N Manual Transmission Input Shaft Seal

Overview of National 4638N Manual Transmission Input Shaft Seal

The National 4638N manual transmission input shaft seal is engineered to provide reliable sealing performance for select Chevrolet, Dodge, and GMC trucks. Designed with durable polyacrylate material, this oil seal helps maintain transmission integrity by preventing fluid leaks and contamination.

• Constructed from high-quality polyacrylate for durability and resistance
• Inside diameter of 1.375 inches (34.930 mm) to fit specific input shafts
• Outside diameter measures 1.989 inches (50.520 mm) for precise housing bore fitment
• Seal thickness of 0.192 inches (4.880 mm) ensures proper sealing pressure
• Redicoat surface treatment enhances wear resistance and longevity
• Part of the National 4000 series, designed for manual transmission applications

Detailed Product Description and Specifications

The National 4638N input shaft seal is specifically designed for manual transmissions in heavy-duty trucks such as Chevrolet Silverado 1500, 2500, and 3500 series, GMC Sierra 1500 through 3500 Classic models, and Dodge Ram 2500 and 3500 pickups. This seal features a 1.375 inch (34.930 mm) inside diameter to fit the input shaft snugly, while the 1.989 inch (50.520 mm) outside diameter matches the housing bore precisely at 1.982 inches (50.340 mm). The 0.192 inch (4.880 mm) thickness provides the necessary sealing width to prevent oil leaks under demanding operating conditions. The polyacrylate material offers chemical resistance and flexibility, maintaining a tight seal over time. Additionally, the Redicoat treatment on the seal surface reduces friction and wear, contributing to extended service life within the transmission assembly.

Applications and Common Issues Addressed

• Prevents manual transmission fluid leaks in Chevrolet Silverado and GMC Sierra trucks
• Protects transmission internals from dirt and contaminants in Dodge Ram 2500 and 3500 models
• Reduces risk of input shaft seal failure due to wear or heat degradation
• Maintains proper lubrication levels to avoid transmission damage
• Helps eliminate noise and vibration caused by leaking seals

Installation Notes and Tips

• Ensure the transmission input shaft and housing bore are clean and free of debris before installation
• Use appropriate tools to press the seal evenly into the housing bore without distortion
• Verify the seal orientation matches the original part to maintain oil retention
• Check shaft surface for wear or damage that could compromise the seal
• Follow vehicle manufacturer torque specifications when reassembling transmission components

Quality Assurance and Warranty Information

National's 4638N input shaft seal is manufactured to meet industry standards for durability and performance. The product undergoes rigorous quality control to ensure dimensional accuracy and material integrity. This seal is backed by National's warranty coverage, providing confidence in its reliability for manual transmission applications on compatible Chevrolet, Dodge, and GMC trucks.