A motor drive assembly for a vehicle is proposed which can prevent a two-way roller clutch of the current speed ratio and a two-way roller clutch of the next speed ratio from engaging simultaneously. This assembly includes a first-speed friction plate (52a) formed with engaging protrusions (66a) on the first-speed side, a shift ring (51) formed with engaging recesses (65). While the shift ring (51) is in a first-speed shift position SP1f, the engaging protrusions (66a) are adapted to be engaged in the engaging recesses (65), thereby preventing rotation of the shift ring (51) relative to the first-speed friction plate (52a). The shift ring (51) is further provided with projections (63) on its inner periphery. The drive assembly further includes an annular protrusion (58) formed with cutouts (62). When the projections (63) are axially and circumferentially displaced from the respective cutouts (62), the projections (63) are adapted to interfere with the annular protrusion (58), thereby preventing axial movement of the shift ring (51) between the first-speed shift position SP1f and a second-speed shift position SP2f.