A multiple-speed ratio transmission mechanism for an automotive vehicle includes a torque input shaft supported on a first axis, and an output shaft and intermediate shaft rotatably supported parallel to the input shaft. Multiple pinion-gear pairs are supported on the three shafts. A planetary gear unit, including a sun gear, ring gear, and a set of planet pinions rotatably supported on a carrier, has its input connected to the intermediate shaft and its output connected to the output shaft. Synchronizers drivably connect a member of the pinion-gear pairs to one of the shafts. A shift mechanism transmits motion of a shift lever to shift forks that move synchronizer sleeves into engagement with the selected gear.