This gearbox gasket seals the interface between the transmission housing and its cover, preventing oil leakage at the joint. It is a flat, non-compressible shim that sits between the two machined faces of the gearbox assembly. A degraded or incorrectly seated gasket allows lubricant to weep past the mating surfaces, which can lead to low oil level and eventual gear or bearing damage. This original-manufacturer gasket is cut to the same thickness as the factory part, so the housing-to-cover gap and the resulting bearing preload remain within specification. On reinstall, clean both sealing faces thoroughly and apply no additional sealant unless the service manual directs otherwise.