Power split devices designed as compound epicyclic four-speed gears are essential components of Hybrid Electric Vehicles both for passenger cars and heavy-duty trucks. There are numerous studies regarding power split models or numerical analyses including state variable choice and model variants. However, different approaches for each gear type are the typical procedure. So it is of generic and urgent interest to overcome diverse parameter definitions and various dynamical models. Generic modelling based on three shafts and numerical power ratio analyses specific to one special four-shaft gear were introduced. The key idea of this paper is to upgrade and generalize these approaches to any four-shaft devices. The objective is one generic power flow model and a generic power ratio research based on generic parameter definitions. Unified parameter sets based on gear construction and geometry assure easy customization and any choice of state variables. Two standard gears, three passenger car gears and one innovative device serve as examples. Gear comparison studies get more comprehensible. This paper applies Bond Graphs. Other power flow representations can be utilized for unified approach suggested as well. (C) 2017 Elsevier Ltd. All rights reserved.