A manually shiftable transmission includes a blocking mechanism to prevent unintended engagement of a first forward gear set. An electronic controller is provided for moving the blocking mechanism into an unblocking position. A manually operable release switch is provided to generate a signal to an electronic controller to move the blocking mechanism into the unblocking position when an intentional engagement of the first gear set is desired. The transmission may also include a mechanism to inhibit engagement of a reverse gear set. The electronic controller and manually operable release switch may be used to move the reverse gear inhibiting mechanism to an uninhibited position.