Much research has been published on gear fault analysis techniques, almost all based on the time synchronous average (TSA). These include and are not limited to: residual analysis, energy operator, energy ratio, amplitude modulation, frequency modulation, sideband index, zero-order figure of merit, etc. Because the TSA is based on tachometer zero cross times, the performance of these analyses is dependent on the quality of the tachometer data. The tachometer signal always has jitter, due to electrical noise, magnetic noise, or manufacturing spacing error of the tachometer target (e.g. gear tooth spacing). By implementing a novel zero phase filter to reduce tachometer jitter, large improvements in the fault detection were observed. For a known gear fault, the separability, related to fault detection, increased from 10 to 25%.