A robotic surgical tool includes a drive housing having first and second ends, a carriage movably mounted to the drive housing, and a shaft extending from the carriage and penetrating the first end, the shaft having an end effector arranged at a distal end. An activating mechanism is secured to the carriage and includes a transmission link pivotably coupled to the carriage, a transmission drive gear rotatably mounted to a transmission link, a drive gear rotatably mounted to the carriage and operatively coupled to the transmission drive gear, and a transmission driven gear rotatably mounted to the transmission link and driven by rotation of the transmission drive gear. The transmission link is pivotable between a first and second positions to actuate the activating mechanism to perform first and second functions, respectively, of the end effector.