A drop hammer for driving a pile comprising a ram member supported within a housing chamber for movement relative to the housing member between the lower position and the upper position and a lifting system for moving the ram member from the lower position to the upper position. When the lifting system raises the ram member above a preload position, ambient air substantially freely flows into and out of the housing chamber through a vent port. When the ram member falls below the preload position, fluid is prevented from flowing through the vent port such that ambient air within a preload chamber portion of the housing chamber compresses to create a preload force that is transmitted to the pile. When the ram member moves into the lower position, an impact force generated by the ram member is transmitted to the pile.