The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes. However, the mechanical properties of metals are greatly affected by thermal operations. So, for evaluating the stress distribution and distortion of teeth profiles in a gear/shaft assembly, a transient thermal analysis is necessary for finding the change in mechanical properties. The friction on the contact surface is another important parameter in interaction of the gear with the shaft. Evaluating the gear stress and deformation fields for several modes of heat transfer and friction coefficients showed that the maximum radial or tangential stresses on contact surface of the joint may have more than 8% increase by increasing friction coefficient; while the intensity of heat transfer at cooling stage has lower effect on stress distribution.