<div class="htmlview paragraph">The paper describes the different types of polyphase, multistage and floating element hydrodynamic torque converters and their variations. Also described are all possible methods of combining torque converters with gearing to alter their performance. The gear systems reviewed are: differentially geared, differential reactors, conventionally geared, and auxiliary element geared. All these systems are also investigated in both input- and output-coupled arrangements. Also shown is a parametric method of representing torque converter performance when more than two elements are permitted to rotate. Equations are disclosed which permit performance calculations for all types of geared element torque converters and combinations.</div>