A driving shank assembly includes a tube, a drive head, a connector, two quick release nuts, and two fastening caps. The tube has two mounting portions each provided with a mounting recess for mounting the drive head and the connector respectively. The two quick release nuts are locked onto the two mounting portions of the tube respectively. The two fastening caps are locked onto the two quick release nuts respectively. Each of the two fastening caps has interior provided with an inner stepped edge. The drive head is provided with a stepped positioning edge abutting the inner stepped edge of one of the two fastening caps. The connector is provided with a stepped positioning edge abutting the inner stepped edge of the other one of the two fastening caps.