An input system includes an input shaft portion, including a first and second input shafts, bearings, rotatably supporting the input shaft portion; and clutches, for transmitting rotational power to the first or second input shafts. An output system includes a first and second output shafts, and a plurality of driven gearwheels, which mesh with drive gearwheels of the first and second input shafts. Driven gearwheels for low gears disposed on the second output shaft are submerged in lubricating oil in an oil reservoir provided below the second output shaft. Drive gearwheels for low gears are disposed adjacent to the bearings. Tooth width dimensions of the drive gearwheels for the low gears are larger than tooth width dimensions of the driven gearwheels for the low gears. Exposed tooth width portions of the drive gearwheels constitute oil splashing portions which splash lubricating oil splashed by the driven gearwheels on to the bearings.