Abstract: A method and performing apparatus for testing the efficacy of the lock-up mechanism for a torque converter on a transmission test machine includes a lock-up switch wired in a manner to simultaneously direct current to the lock-up solenoid of the transmission under test and a digital clock. The current is provided by the associated electrical system of the operating prime mover of the test machine. A simulated axle load on the test machine is braked to preclude rotation of the transmission's output shaft connected thereto. Upon operation of the prime mover, the transmission shifts into high gear and current from the electrical system is directed to the solenoid and clock by closure of the lock-up switch. Upon proper engagement of the lock-up assembly, the direct drive established between the driven and braked output shaft precludes rotation of the drive shaft. This preclusion of rotation shuts down the prime mover and cuts off generation of the current by the associated electrical system.