To determine the rolling contact fatigue (RCF) strength of cryogenic treated gear and bearing steels, an experimental test rig based on nut-cracker mechanism is designed and developed in the laboratory. The test rig is designed for variable load, speed and lubrication condition. The failure monitoring is done using signals acquired from vibration and sound of the contacting rollers. The online monitoring and post processing of the signals is done in LabView and MatLab software, respectively. In the experimental studies, the effectiveness of the vibration and sound signals as a condition monitoring tool in predicting RCF failure is analyzed. © 2007 Elsevier B.V. All rights reserved.