Timken 312518 Manual Transmission Shift Shaft Seal

Timken 312518 Manual Transmission Shift Shaft Seal

Timken 312518 is a manual transmission shift shaft seal built to retain lubricant at the shift shaft while helping block dirt and debris from entering the transmission. It uses an S-Nitrile sealing material and a reinforced outer case to support a secure installation in service applications such as Chevrolet G20, G30, P20, and P30 models, along with GMC G2500, G3500, P2500, and P3500 vehicles.

Key Features

• Manual transmission shift shaft seal for transmission gasket and sealing system service
• S-Nitrile construction for sealing performance in lubricant-exposed applications
• Reinforced outer case helps reduce installation damage and improve durability
• Ribbed rubber inner diameter helps seal minor spindle imperfections and promote seating
• Internal contamination exclusion system helps limit debris penetration that can lead to leakage
• Vent holes allow lubricant flow around the seal lip to help manage heat build-up
• Timken part number 312518 for direct identification and service matching

Detailed Description

Timken 312518 is engineered for manual transmission shift shaft sealing where lubricant retention and contamination control are critical. The seal’s ribbed inner diameter helps maintain contact on shafts with minor surface variation, while the reinforced outer case supports installation and long-term durability. Vent holes are incorporated to allow lubricant circulation around the lip, helping carry heat away from the sealing area. This part cross-references Bosch 7410 and 7411 for the same application.

Compatible With 1967-1974 GMC G25/G2500 Van, 1975-1978 GMC G25, 1975-1978 GMC G35, 1975-1980 Chevrolet Monza, 1975-1981 Chevrolet P20, 1975-1981 Chevrolet P30, 1975-1985 Chevrolet G30, 1975-1987 Chevrolet G20, 1976-1979 Buick Skyhawk, 1976-1979 Pontiac Sunbird, 1979-1981 GMC P2500, 1979-1981 GMC P3500, 1979-1985 GMC G3500, and 1979-1987 GMC G2500.

What It Helps Address

• Transmission fluid seepage at the shift shaft
• Debris intrusion into the sealing area
• Leakage caused by minor shaft surface imperfections
• Heat-related seal wear from poor lubricant circulation
• Installation damage to the seal housing or outer case

Installation Notes and Tips

Verify shaft diameter, housing bore, and seal width before installation: 0.750 in shaft diameter, 1.000 in housing bore, and 0.126 in width. Clean the bore and shaft thoroughly, inspect for scoring or burrs, and install the seal squarely to avoid lip distortion. Confirm the transmission application against the vehicle listing before service on Chevrolet G20, G30, P20, P30, and GMC G2500, G3500, P2500, and P3500 models.

Quality Assurance

Timken designs its oil and grease seals with precision sealing features, contamination exclusion, and durability-focused construction for drivetrain service.