Ram Gas/Diesel Engine Sound 4" RAM38 Ram engine sound system. You can choose gas or diesel sound. Adjustable horn. Can be used with cars, trucks, or boats. Sound is synchronized with actual speed of vehicle. This package includes;One 4" speaker One control unit One servo activated micro switch One circuit board There is 12" of wire between the speaker and the circuit board. From the circuit board there are three series of wires. One set goes to power so