An all-terrain vehicle having an improved parking locking mechanism disposed within the housing of a transmission assembly. The parking locking mechanism includes a locking-lever guide disposed eccentrically about the axis of rotation of the shift drum and a locking lever having a body with an opening therein engaging the locking-lever guide. The guide and the opening constructed and arranged to cooperate with each other such that rotation of the shift drum moves the locking lever into locking engagement with one gear of the transmission.