This investigation utilizes a DFSS analysis approach to determine automatic transmission gear content required to minimize fuel consumption for various powertrain - vehicle systems. L18 and L27 inner arrays with automatic transmission design and shift pattern constraint parameters were varied to determine their relative influence on fuel consumption. An outer noise array consisting of two vehicles with various engines, final drive ratios and legislated emissions test cycles was used to make a robust transmission selection based on minimizing fuel consumption. The full details of the DFSS analysis method and assumptions are presented along with a detailed examination of the results. With respect to transmission design parameters, parasitic spinloss and gear mesh efficiency were found to be most important followed by the number of gears. The DFSS analysis further revealed that unique transmission design formulations are potentially required for widely varying engines. The shift pattern constraint of minimum operating speed in gear that establishes the downshift line was found to be most significant while all other shift parameters proved to be negligible. An average 0.4 to 0.8% decrease in fuel consumption could be realized by optimizing the transmission for a given engine - vehicle combination with the underlying assumptions of the energy analysis. For a given transmission - vehicle, changing the engine resulted in an average 2 to 5% reduction in fuel consumption depending on the specifics of the engine technology.