Shaft oil seal

In machinery, a device that prevents the passage of fluids along a rotating shaft. Seals are necessary when a shaft extends from a housing (enclosure) containing oil, such as a pump or a gear box.

A common type of shaft seal consists of an elastomer (elastic rubberlike) ring bonded to a metallic ring that is a press (tight) fit in the hole in the housing through which the shaft extends. The sealing is done by a lip on the elastomer ring that is pressed snugly around the shaft by a helically wound garter spring. When properly designed and installed, the lip rides on a film of lubricant about 0.0001 inch (0.0025 millimetre) thick. If the film gets too thick, fluid  leaks; if it is too thin, the lip gets hot, and the seal may fail. Leather, synthetic rubber, and silicones are among the materials used for the sealing ring.

Gearbox oil seal

A gearbox oil seal is a component of a transmission system that helps to keep the transmission fluid inside the gearbox. It is a rubber seal that fits around the outside edge of the gearbox, preventing the fluid from leaking out and contaminating the surrounding area.

Auto oil seal structure 
The oil seal is generally composed of three basic components: sealing element, metal shell and clamping
spring.Types of oil seals include single and double lips, rubber or polymer, metal housing, spring loaded, and internal, externaland axial guides.