a parallel hydromechanical continuously variable transmission has a housing that holds a make - up pump , and has internal cavities for holding operating assemblies of the transmission , including an axial piston pump and an axial piston motor . the pump and motor each have a rotating element and a non - rotating element . each rotating element has a center of mass and an axis of rotation that passes through the center of mass . each non - rotating pump element is mounted for tilting movement on trunnions in its own respective pair of mounting journals in the housing . the tilting axes of the non - rotating elements lie transverse to the axes of rotation of the rotating element . the pump and the motor are disposed side - by - side in the housing with the axes of rotation approximately parallel to each other . a stationary manifold , fixed to the housing , has one surface in contact with the rotating pump element and a second surface in contact with the rotating motor element . fluid passages open in the two surfaces in fluid communication with the pump and motor cylinders through a pump / manifold interface . internal fluid passages in the stationary manifold convey fluid pressurized in the pump directly to the motor , and convey spent fluid displaced from the motor back to the pump . the transmission ratio is controlled by the tilt angle of the non - rotating pump and motor elements . a tilt angle control apparatus attached to the housing and to the non - rotating pump and motor elements governs that tilt angle .