An automatic transmission for a vehicle having a torque converter driven by an engine, an input shaft driven by the torque converter, a gear train driven by the input shaft, an output shaft driven by the gear train, a counter drive gear fixed to the output shaft at one end thereof opposite the input shaft, a counter shaft substantially parallel to the output shaft, a counter driven gear fixed to the counter shaft at one end thereof and meshed with the counter drive gear, a differential drive pinion gear fixed to the counter shaft at the other end thereof and meshed with a drive gear for a differential gear, first and second tapered roller bearings near the counter driven gear and the differential drive pinion gear, respectively, for supporting the counter shaft, said counter shaft being accommodated in a counter shaft chamber of a transmission casing, said counter driven gear being accommodated in a transfer chamber adjacent to the counter shaft chamber and separated therefrom by the first tapered roller bearing, transmission oil stored in the lower spaces of the counter shaft and transfer chambers, the lower portions of the counter driven gear and the first tapered roller bearing being immersed in the oil. A disc-like oil deflector having a central aperture is fixed to the inner wall of the counter shaft chamber adjacent to the first tapered roller bearing. The counter shaft is inserted loosely into the central aperture of the oil deflector.