A transmission control apparatus for controlling a vehicle's transmission. The apparatus includes (i) a control motor mechanically connected to the transmission's selector drum and is actuable to rotate the selector drum, (ii) a torque sensor which senses torque applied to the selector drum by the control motor, (iii) a controller configured to control the control motor based on signals received from the torque sensor to control the engagement/disengagement of the dog clutches; and (iv) a cam indexer connected to the selector drum. The cam indexer includes (i) a cam sprocket having one gear detent corresponding to each of gear engagement position of the selector drum, and one neutral detent corresponding to each neutral position of the selector drum, and (ii) a cam follower that engages with the gear detents and biases the selector drum into either a corresponding gear engagement position or a corresponding neutral position.