For designing machines and devices the dimensioning with respect to service life is increasingly taken into account. This applies also for gearing which are still today one of very important components of almost all machines. The problem of determination of the service life of gearing is directly related to geometry of gears, multiaxial loadings, materials and appropriate models for prediction of the crack propagation. Obviously gears and gearing belong to the real complex structure, by correctly selected and carefully planned experiments we obtained results with which we can confirm and justified the mathematical model for calculating different parameters, i.e. service life.