In a chamber R1 which accommodates a transmission device comprising a drive pulley 8, a driven pulley 9 and a belt 10, a cover 51 is provided to cover the lower peripheral portion of the drive pulley 8 along the periphery. The drive pulley is positioned below the driven pulley, and raised portions 52 which are used for the detection of the rotational speed of the drive pulley are provided on the periphery of the drive pulley. The end surface 51bs of the cover facing the inner wall 54 of the pulley chamber is positioned away from the inner wall with a clearance V therebetween. In a vehicular transmission which is constructed in this arrangement, the amount of lubrication oil that flows near to the periphery of the pulley which is positioned lower is comparatively small. Thus, this arrangement restricts agitation of the lubrication oil, which may be caused by the raised portions of the rotating pulley. Therefore, loss in the rotation of the pulley and oxidation and degradation of the lubrication oil are effectively prevented.