Master thesis is focused on solving and assigning on impact of distortions gearbox components as well as their impact on the accuracy of gear mesh, which is essential for proper functioning and also in terms of the life of the transmission. The work is aimed to determine the effect of gearbox housing deformation to touch the gears, which are currently not taken into account when gearbox are designing. At the beginning of the work theoretical knowledge of gears are given. Analyses gearbox model is designing in the next sections. Next, the work deals with the gearbox strength analysis and the analysis of the selected contact healical gear, taking into account the deformations of teeth, shafts and also the gearbox housing. In conclusion the work includes analyse of optimized gear mesh.