Damaged or worn out gears and roller bearings give a clear frequency signature.
With the FFT diag plug-in, tools such as side bands markers or envelope analysis give key information for the analysis of damaged roller bearings. For gear box analysis, kurtosis calculation or cepstrum analysis will detect teeth defects.
On this type of machinery, it is often difficult to get a tach or a keyphasor signal on the desired shaft: virtual tachs let you define wheel ratios between different shafts in order to process order analysis or FFT analysis.