Abstract: A hydraulically propelled vehicle has a vehicle body with a pair of forward wheels and a pair of rearward wheels. A single fluid displacement pump is operatively connected to each wheel. A fluid displacement motor is connected to each wheel. The pump is fluidly connected to each motor. A steering angle sensor is located adjacent each wheel to sense the angular position of each wheel. The speed sensor is on each motor to measure its rotational speed output. A fluid displacement actuator is on each motor to set the fluid displacement thereof. A fluid displacement computer controller is operatively connected by electronic impulse to the speed sensors. The fluid displacement actuators and the steering angle sensors are operatively connected to the controller so that the controller can obtain information therefrom to calculate the expected speeds for the motors.