A tractor transmission is usually very complex with a lot of gear pairs, shafts and bearings in it. Modern transmissions have also several functionalities like shifting without clutch, 4WD/2WD forward/reverse shuttle and PTOs. They must work smoothly and quietly like an automotive transmission, but usually working condi-tions are much more severe. They must also be reliable in different kind of working conditions and fields of applications. Due to the wide variety of gears and speeds that can be chosen, calculations for safety factors and lifetime of components are typically very complicated, time consuming and difficult to manage. It is laborious, unproductive and error-prone to administer the many calculations that occur in a tractor transmission due to its complexity. The use of a calculation model, that sim-ultaneously administrates all the calculations, brings many advantages for the man-ufacturing process, planning of tests and sales support. A very complex and modern transmission was modeled in this project in order to be able to simultaneously meas-ure the entire tractor transmission driveline. Tractor with 12x12 driveline shifting system and power flow variations can be calculated the whole system’s gears, shafts, bearings with a load spectrum.