Abstract: A shift control device adapted for installation on a conventional pneumatic transmission control switch for trucks to convert its lever action to an easily controllable twisting or turning action and one that prevents inadvertent "down-shifting." The device includes a ball-like knob adapted for connection to the head of a standard pneumatic transmission control with a radially extending fork portion that fits over the lever for the control. The knob is rotatably supported on a central pin attached to the control head so that turning it will move the control level, its travel being limited so that downward force must be applied on the knob before the control lever can be moved to its low range position.