Abstract: An apparatus and method is disclosed for testing automatic vehicular transmissions. The transmission tester of the invention includes input adjustment elements and output adjustment elements which permit various makes and models of transmissions to be installed in the tester for testing. The torque converter of the transmission under test is operatively connected to a drive shaft of the transmission tester. The output of the transmission under test is operatively connected to a load device which provides a loading torque to the output shaft. During the test procedure, the torque converter is rotated at varying speeds while a loading torque is imparted to the output shaft. A vacuum is supplied to the vacuum modulator control of the transmission under test, and the hydraulic pressure of the transmission under test is monitored.