The implementation of powder metallurgy for high performance automotive transmission gears has the potential to replace the conventional wrought steel manufacturing chain in a near future. Several studies have shown the possible benefits of this implementation in terms of manufacturing costs, times and product performance. The main limitation of this transition is the inferior mechanical strength of the PM gears, which may implicate in shorter fatigue life. With the advance of the technique, however, the strength of PM gears have been improved, getting closer to that of the wrought steel ones. Nonetheless, the powder metallurgy chain has as characteristic effects of microstructural heterogeneity, due to the porosity and the grain orientation caused by surface densification. A consequence of this is a heterogeneous state of residual stresses, that may affect the fatigue behavior of such gears. The present dissertation, then, has as objective the comprehension of the RS heterogeneity state of PM gears. It is based on the hypothesis that such heterogeneity can be assessed through X-ray diffraction methods. Hence, two research questions were formulated to guide this study. The first question is about the most suitable method for this assessment. The second question is about how significant is the effect of the PM chain on the RS heterogeneity of gears. According to these questions, RS mappings and X-ray diffraction line broadening analysis were applied to the surface of the flank of gear teeth correspondent to successive steps of the PM and wrought steel manufacturing chains. Correlational surface integrity assessments, such as metallography, topography analysis and hardness mapping, were also performed to support the RS results. From the methodology analysis, the line broadening was the most suitable method for investigating single process steps, and both methods are indicated for comparing different manufacturing steps and chains. It could then be observed that the RS heterogeneity of gears is manifested in two levels (macro and micro RS) and three types of distribution (along the lead, along the involute and diffuse). From the evolution of the heterogeneity along the PM chain, it was found that each of the process steps is associated to a characteristic RS heterogeneity. It could also be perceived that the heterogeneity of RS is propagated along the chains analyzed. Therefore, the present study contributes to the knowlegde of PM gears for their lifetime optimization, whose consequences can benefit the powder metallurgy and automotive industries.