The fluid in the transmission helps carry heat away from friction points. If there is not enough fluid in the transmission due to damage or a leak, it could begin to overheat, which may cause further transmission and engine damage. One of the most common causes for an automatic transmission leak is the improper installation and, or a worn or damaged output shaft transmission seal. This seal is located at the rear of the transmission on the output shaft. This seal is built and produced by NOK Corporation.