An improved automatic transmission is disclosed which includes a planetary gear mechanism and a wet type centrifugally operated clutch for controlling power transmission from a rotating input member to an output member. The clutch is connected to the input member for integral rotation therewith and disposed in a casing at a location close to the planetary gear mechanism. A drive chain for transmitting power from the output member to a driven member is disposed in the casing at a location close to the planetary gear mechanism on the opposite side of the clutch. One or both of the clutch and the chain is/are immersed in a lubricating oil sealingly contained in the casing so that the lubricating oil is scooped up by means of the clutch or chain in accordance with the rotation of the input member so as to be supplied to the planetary gear mechanism.
