Transaxle fluid, sometimes called automatic-transmission fluid, is a type of fluid that keeps the transaxle of a front-wheel-drive vehicle lubricated and functioning properly. The transaxle is an auto part that combines in one housing the transmission with the differential, thus making the car shift gears automatically.
Modern transaxle fluid is typically made of chemical compounds that lubricate the parts. These compounds often include additives to prevent wear, inhibitors to prevent rusting, detergents, dispersants and other compounds to keep the transmission running smoothly. Transaxle fluid contained whale oil and other organic compounds until the 1970s, but that type of fluid has been discontinued.