Abstract: An overdrive transmission for a motor vehicle has a housing with a rotatably mounted driving shaft and a rotatably mounted driven shaft. A planetary gear device is used to transmit power from the driving shaft to the driven shaft. In two of the illustrated embodiments, when the transmission is in the direct drive mode the planet gear carrier of the planet gear device is allowed to rotate and is engaged with the driven shaft by a clutch for power transmission at a 1:1 ratio, and when in the overdrive mode the planet gear carrier is prevented from rotation by another clutch and is disengaged from the driven shaft for power transmission to the driven shaft through the planetary gears of the planetary gear device at an increased gear ratio.

Abstract: An auxiliary transmission unit having multiple countershafts is disclosed for use in a motor vehicle. The countershafts are disposed about an input sun gear and an output sun gear in such a manner as to provide an opening for a shift fork to reach a central shift mechanism locating the planet gears, one with respect to the other, at angular alignment positions in an unequally spaced manner. A tooth of one sun gear at an alignment position will be aligned with a tooth of the other sun gear at least once during one revolution of a countershaft. The unequal spacing of the countershafts provides reduced height for the auxiliary transmission housing.