Travelling system transmission structure for vehicle

The traveling system transmission structure for vehicle includes a planetary gear unit, a forward/rearward-travel switch unit and a transmission case. A front end portion of a sun gear shaft is directly or indirectly supported by a front bearing wall that is detachably connected to a front side of the transmission case and a rear end portion of a planetary outputting member is directly or indirectly supported by an intermediate bearing wall, so that the planetary gear unit is accommodated in a front chamber that is sandwiched by the front bearing wall and the intermediate bearing wall. A front end portion of a forward/rearward-travel input shaft is directly or indirectly supported by the intermediate bearing wall and a rear end portion of a clutch shaft is supported by a rear bearing wall that is detachably connected to the rear side of the transmission case, so that the forward/rearward-travel switch unit is accommodated in a rear chamber that is sandwiched by the intermediate bearing wall and the rear bearing wall.