Intensified EU CO2 regulations for heavy-duty trucks until 2030 are driving significant technological progress of electrified powertrains in this segment. Currently, the market shows no definitive trends regarding drivetrain topologies. This refers to systems such as electric axles or central drive topologies, as well as to specific parameters like the number of electric motors, gear modes, and gear stages. Unlike the passenger car industry, the truck sector operates with smaller production volumes, prompting OEMs to strive for optimal portfolio coverage through powertrain platform strategies. Thereby, development departments need to consider a broad range of partly contradicting vehicle requirements by weighting the corresponding vehicle application importance. Moreover, the conflicting goals of minimizing the number of platform components and optimizing the powertrain efficiency of each portfolio vehicle must be evaluated. This paper provides an overview of current drivetrains for heavy-duty trucks and examines the development process of an electric drivetrain. Additionally, a methodological approach for an automatic design of a drivetrain platform for electrified trucks is proposed. Key steps include portfolio analysis, power level definition, variation of drivetrain components, and overall drivetrain optimization. The components variation is realized by adjusting parameters e.g. number of electric motors and gears and varying parameters e.g. number of teeth or widths of gears in the transmission.