A suspension system has a pair of cylinders connected between the cab or axle and a chassis of a vehicle to isolate the driver from vibrations. A pair of hydraulic cylinders is coupled to opposite sides of the cab or axle and to the vehicle chassis. A separate accumulator is coupled each hydraulic cylinder to act as a hydraulic spring that attenuates side to side motion. A leveling valve selectively control the flow of fluid to or from both hydraulic cylinders to level the cab or seat in response to load changes.