The present invention is a drop-down extra axle and wheel set for a utility truck. The extra axle and wheels are pivotally connected to an extra frame set that overlies and/or extends along the original frame for the truck, from the back end of the truck frame to near its midpoint just behind the cab of the truck. The extra frame set is a generally horizontal, rectangular piece that lays over the top of, and/or extends along, from the back end of to just behind the cab of, the original truck frame. The extra frame set has a trailing, extra, axle support assembly near its back end. The extra axle support assembly depends down from the extra frame, and supports an extra axle and wheel set at its bottom. A set of pivoting connecting rods extend forwardly from the bottom of the extra axle support assembly to pivot brackets which also depend down from the extra frame several feet forward of the extra axle support assembly. The position of the extra axle support assembly, either wheels-down on the roadway, or wheels-up off the roadway, is determined by a set of air bags, one on each side, enclosed in the extra axle support assembly.