The tooth surface temperature rise during meshing spur gear pair due to frictional heat is investigated. A coupled thermo-elastic analysis is carried out by considering the elastic deformation of teeth and corresponding load shearing between the contacting tooth pairs and heat generation in the contact. In the analysis, gear pairs with contact ratio between one and two are considered and pinion and gear are modeled only with three teeth. The finite element analysis is performed using quadrilateral 4-node plane-strain elements. The analysis is focused on the contact surfaces so that relatively fine mesh is used for contacting involute teeth profiles. Constant rotation is applied on the pinion and the gear is resisted with a constant torque by a torsional spring. The load sharing between the pairs in contact along the pressure line is determined by elastic contact analysis. The sliding velocity and contact pressure is calculated for each node in the contact area and the frictional heat is evaluated by assuming a constant coefficient of friction. The convection heat transfer coefficient on tooth surfaces in the lubricated conditions based on experimental studies is also included in the solution. The effects of involute tooth profile modifications on temperature rise are also investigated. The results of the surface temperature rise obtained by coupled thermo-elastic contact analysis and analytical calculations are compared with the experimental results in the literature. Finally, it is observed that the surface temperature rises on spur gear teeth pair along the pressure line are highest at the very beginning of the meshing and the surface temperatures at the initial contacts can be decreased by profile modification at the tip of the tooth. (c) 2006 Elsevier B.V. All rights reserved.