Abstract: This is a suspension system for use on a vehicle between an axle and a load carrying body. It includes a plunger tube which is attached to the axle of the vehicle. The plunger tube extends upwardly into the annulus between an outer cylindrical housing, which is secured to the frame of the vehicle, and an interior piston rod. There is a main cavity within the piston rod and an annular cavity between the piston rod and the plunger tube. At least one orifice extends through the piston rod to permit fluid communication between the main cavity within the piston rod and the annular cavity. A second passage therebetween includes a ball check valve which permits flow of fluid only from the main cavity to the annular cavity. A movable orifice metering ring can be raised or lowered from the exterior of the suspension system to vary the size of the orifice between the main cavity and the annular cavity.