A vehicle incorporates a gravity-assist energy harvesting suspension system including one or more gravitational positive displacement pumps. The positive displacement pump has a cylinder and a reciprocating piston inside the cylinder. The piston is adapted for movement along a compression stroke and an opposite extension stroke in response to a gravitational bounce of the vehicle when in motion. A turbine comprising a rotor shaft and attached blades is mounted relative to a distal end of a fluid outlet hose connected to the pump. Fluid discharged through the outlet hose acts on the blades, thereby moving and imparting rotational energy to the rotor shaft. A generator is operatively connected to the turbine, and is adapted for converting the rotational energy generated by the rotor shaft to electrical energy.