The purpose of this paper is to analyze the durability behavior of helical gears in manual automotive gearboxes. It shows the evolution of a certain mating gear applied in a specific durability vehicle test where the gears were modified in some design parameters, such as material type, shot-peening, increase of gear width and lead corrections (micro-geometry). This paper intends to evaluate some design parameters and gear life factors that define the mating gear durability and compare the theoretical results against to the practical ones. These gear life factors (application factor, contact factor, material type, etc) are enclosed in known standards (i.e. DIN 3990).
The study shows the necessity of testing automotive transmissions in the beginning of design development. This is the best way to identify some failure modes that were not foreseen by the first calculations and hypothesis. Through the practical results (vehicle test) the study will conclude which is the main design parameter that allowed the mating gear fulfilled the test requirements regarding tooth breakage.
By the end intends to propose some other design changes to be evaluated that may reduce the product cost. Reminding that the drivers for the automotive industry are to provide quality, light and cheap products, through the research is possible to optimize it.