Gear tooth crack is a type of fault which need monitoring to prevent serious damage to the operating condition of the gear system. In this research work an analytical model is proposed to investigate the effect of gear tooth crack in the form of time varying gear mesh stiffness. In this case the tooth crack propagations is monitored along tooth width, crack depth and crack height are incorporated in this model for simulation of gear tooth root crack. Analysis is started with very small crack size to reflect in results the early stage of fault occurrence Analytical formulation is helpful in finding the mesh stiffness of a spur gear pair with different crack length, width and depth variation. The developed analytical model can predict the change of gear mesh stiffness with presence of a gear tooth crack and also compares the mesh stiffness data with one contact period of gear pair. The analysis is done with the gear pair having more than one tooth in contact during some part of the contact period. This gives single or double tooth contact in one period. Analytical results shows less stiffness when single tooth pair contact occurs for part of TVMS diagram and higher stiffness for remaining part due to double tooth contact.

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