Oil can leak from an automatic transmission in the following directions:
Internal leaks:
* Worn or damaged shaft seals, splines or drain plug gaskets
* Faulty oil pump or gearbox housing
External leaks:
* Cracks or holes in the transmission housing
* Damaged hydraulic tubes or hoses
* Transmission breather valve leaks when oil pressure is excessive
Evaporation:
* Minor oil evaporation may occur through the breather or during prolonged operation under load
Overspending:
* Incomplete draining of old oil before changing, resulting in overflow and expulsion of excess oil
* Burnout of friction discs, which leads to the formation of metal particles and oil contamination, which can cause leaks