A vehicle and drive system control method for a vehicle including first and second traction elements coupled to the vehicle, a variable displacement pump, a bi-directional variable displacement first motor coupled to the first traction element, and a bi-directional second motor coupled to the second traction element. The pump, and first and second motors are coupled fluidly in series with one another. A control unit can determine a desired speed for the traction elements, and determine pump, first and/or second motor displacements based on the desired speed. First and second speed sensors can sense output speeds of the motors, and the pump, first and/or second motor displacements can be determined based on the motor output speeds. Articulation and steering sensor signals can also be used to determine pump, first and/or second motor displacements.