This gearbox gasket seals the joint between the gearbox housing and its cover, preventing oil leakage and maintaining internal pressure for proper lubrication of the gears and bearings. It is a service item that must be replaced whenever the gearbox cover is removed for inspection or repair. A degraded gasket allows oil to weep from the mating face, leading to low oil level and eventual gear or bearing damage. This original part is manufactured to the same thickness as the original assembly, so the cover bolts torque to the correct clamping force without over-compressing the seal. On reinstall, clean both mating surfaces thoroughly and apply the specified torque to the housing bolts.