A single transmission can contain dozens of sealing components, all with a specific purpose. If even one of those seals fails, the transmission in the vehicle can begin to leak transmission fluid. A transmission leak isn't simply an issue in itself, however; leaking seals can quickly lead to a multitude of other problems, including total transmission burn out.The purpose of an oil seal is to prevent lubricant leaks by closing in the spaces between a transmission's parts. The seals also prevent dirt and other contaminants from clogging up the unit. A static seal, such as a simple O-ring, fits between two stationary parts, while a more complex, dynamic seal has multiple lips and acts as a barrier between a stationary and a moving part.