A sprocket box for increasing the gas mileage of a vehicle with an automatic transmission is positioned between the back of an engine block and the torque converter. The sprocket box is fed the rotational motion from the engine and doubles the rotational motion being fed into the torque converter in order to increase the fluid pressure felt within the torque converter. Thus, the sprocket box is used to increase the fuel economy of the vehicle. The rotation motion from the engine is transferred and modified by the sprocket box by using an input assembly of sprockets and a roller chain and by using an output sprocket of more sprockets and another roller chain.