The swash-plate in a variable displacement pump experiences very large forces and moments that try to dislocate its position and therefore a large device is required for adequate control. In this paper, the dynamics of an alternative pump design using an indexing valve plate to position the swash-plate are reported. The indexing valve plate design is aimed at controlling the pressure transition for a piston, which is moving from a high-pressure port to a low-pressure port and back. In this paper, the governing equations for the pump are derived and the detailed open-loop, which is necessary for understanding the overall dynamic characteristics of the pump, is reported. Also, linear and nonlinear modeling approaches for the system are compared.