Timken 251511 Manual Transmission Input Shaft Seal - Front

Timken 251511 Manual Transmission Input Shaft Seal

The Timken 251511 manual transmission input shaft seal is built for front-position applications that need a precise seal at the transmission input shaft. It uses S-Nitrile material and a reinforced outer case to help maintain sealing integrity during installation and in service.

Compatible With 1975-1979 Chevrolet Monza, front; 1978-1979 Oldsmobile Cutlass, front; 1978-1979 Oldsmobile Cutlass Supreme, front; 1976-1979 Oldsmobile Starfire, front; and 1978 Oldsmobile Omega, front.

• S-Nitrile construction for sealing performance in transmission service
• Outside diameter: 1.634 in. / 41.50 mm
• Shaft diameter: 1.250 in. / 31.75 mm
• Housing bore: 1.625 in. / 41.27 mm
• Width: 0.188 in. / 4.78 mm
• Reinforced outer case helps reduce installation damage
• Ribbed inner diameter helps seal minor shaft imperfections and seat securely
• Internal contamination exclusion system helps block debris entry
• Vent holes promote lubricant flow around the seal lip to reduce heat buildup

Detailed Application Overview

Timken 251511 is a manual transmission input shaft seal for front-mounted applications in Chevrolet Monza and Oldsmobile Cutlass, Cutlass Supreme, Starfire, and Omega models listed above. This seal is used at the transmission input shaft to retain lubricant and keep contaminants out of the sealing area. This part cross-references Gates (e.g., 12325, 12329) for the same application.

Common Problems This Seal Can Address

• Transmission fluid seepage at the input shaft area
• Contamination entering the transmission through a worn seal
• Leakage caused by minor shaft surface imperfections
• Seal damage during removal or installation
• Heat-related seal wear from poor lubricant circulation

Installation Notes and Tips

Verify shaft diameter, housing bore, and seal width before installation. Clean the bore and shaft surface thoroughly, and inspect for scoring or wear that could affect sealing. Proper seating is important for front-position manual transmission service on the listed Chevrolet and Oldsmobile applications.

Quality Assurance

Timken oil and grease seals use precision sealing designs, reinforced construction, and contamination-control features to support reliable transmission sealing performance.