This gearbox output shaft oil seal is a core sealing component mounted at the rear output shaft end of FAW J7 heavy truck transmission. It serves two key functions: retaining transmission gear oil inside the gearbox to prevent oil leakage, and blocking dust, mud and water from infiltrating the gearbox interior to protect gears and bearings. Adopting fluororubber composite sealing lip plus rigid metal skeleton structure, it withstands high temperature, high rotating speed and sustained vibration generated during long-distance heavy-load transportation. The spring-loaded precision sealing lip ensures stable contact pressure against the rotating shaft, reducing friction heat and wear. Every oil seal undergoes leakage and aging inspection before shipment. It resolves gearbox rear end oil leakage and premature internal component wear, acting as an essential replacement spare part for heavy truck transmission overhaul.