Abstract: A method and apparatus for testing an elastomeric torsional vibration damper by oscillating the hub thereof on a shaker table to thereby simulate actual conditions of use. Prior testing methods and apparatus have not compensated for changes in the mechanical properties of the elastomer which often occur during testing. Such changes are usually due to build-up of heat within the elastomer. According to the practice of this invention, changes in the mechanical properties of the elastomer are compensated for by continuously monitoring the phase difference between the hub and the inertia ring. If the phase difference varies from a predetermined amount, the hub input frequency is then varied in such a manner as to maintain the predetermined phase difference between the hub and inertia ring. In this manner a predetermined phase difference may be maintained throughout the test.