The paper addresses the issue of identifying a technical state of rotating parts with the use of vibrodiagnostics. This method has been developing rapidly for recent years and is assumed to be used for predicting failure occurrence. In this paper we focus on monitoring a technical state of a medium truck bearing box where we simulate different field conditions and their dependence on the RMS – root mean square. A measuring device DEWE 50/8 including the DEWEsoft software product of the Dewetron company have been used for the actual measurement. The aim of the work is to calculate the values of root mean square acceleration up to the moment a failure occurs. In the next step we will put the values into a graph and try to determine a gRMS limiting value. In the future this enables us to change the bearing before a failure occurs otherwise it would increase the related cost.