Based on the analysis of the indicators of functionality and structure of the trolleybus’s traction transmission (TT), some characteristic differences have been established for the classification of 4 generations of drive axles (DA) structures of known world manufacturers. The calculation models and methods for increasing the probability of a fail-safe transmission’s and DA system work, consisting of aggregates, modules, mechanisms, parts and connections, are analyzed. A method is proposed and example is given of predicting the parametric reliability of a planetary wheel gear (PWG) in DA system by two criteria: fatigue strength and vibration resistance of "criteria element" – thin-walled epicycle of "weak link" – PWG.
