A variable force windshield wiper system for an automobile has a rod which is slidably received within a bore of the drive shaft of the wiper system. The end of the rod contacts a lever arm when the rod extends out from the drive shaft. The lever arm is connected to a spring. The other end of the spring is connected to the windshield wiper arm. As the distance of the rod outside the drive shaft increases, the lever arm rotates about a fulcrum and extends the spring thereby increasing the downward force of the wiper arm toward the windshield. To move the rod, a cam having a threaded exterior surface is mounted on the drive shaft and is attached to the rod. A nut having a threaded interior surface engages the threads of the cam. The nut and cam rotate together if no wiper force change is desired The exterior surface of the nut has ratchet teeth. A pawl is used to selectively engage the ratchet teeth of the nut. When an increase or decrease in force for the wiper arm is desired, the pawl is used to engage the ratchet surface to prevent the nut from rotating. The cam will travel up or down the drive shaft when the nut is prevented from rotating. As the cam moves relative to the drive shaft, the rod moves the lever arm.