The gear test rig with variable center distance is a test machine with power circuit. The drive gearbox and the test gearbox are frictionally engaged by two torque shafts (hereinafter only mentioned as shafts). For load application a clutch is provided on shaft 1. The temperature in the test gearbox can be set and controlled. The test rig is driven by an electric motor. The speed is 2000 rpm. The variable-speed test rig allows speeds from 100 rpm to 4000 rpm and two directions of rotation. The load can either be applied by a weight system or with the tension ratchet or with an automatic load system. The special feature of this test rig is, that variable center distances are obtainable by means of adapter plates and therefore different gear pairs can be tested.