Failure Analysis of a Jeep T90 Transmission Gear

A 1949 Jeep transmission gear was examined in this failure analysis. This gear was from a Borg-Warner T90 three speed manual transmission and presented with nearly every tooth on the gear fractured. Regions that appeared melted and smooth were also present on the surface of the gear. This presentation will present the fractographic analysis of this transmission gear teeth, the differences observed in regions on the gear, and metallographic cross-sectional analysis to examine the microstructure and hardness of the gear used to determine the cause of the fractures.