Modifying a longbox on your truck to a shortbox is done by mounting a shortbox onto the frame. To do this, you will need to first remove the longbox from the frame. However, a shortbox is typically not designed to fit on a longbox frame due to the difference in length. The mounting of a shortbox on your truck will require properly fitting it onto the frame.
Instructions
- 1
Open the gas cover on the side of your truck. Locate the small bolts and nuts that are used to secure the neck of the gas tank to the longbox. Remove these with a standard wrench and socket wrench. Remove the gas cap.
2Locate the wiring connectors on the underside of the longbox for the rear lights. Unplug the connectors to disconnect all the wiring from the bed.
3Examine the underside of the truck bed and locate all the mounting bolts. You should see one to two bolts with a nut that are used to secure the longbox to the frame. Remove the nuts from the bolts with a standard wrench and a socket wrench. If the nuts do not come out easily, soak them by using a lubricant spray. Allow the lubricant spray to penetrate the threads of the bolts for at least 10 minutes.
4Lift the longbox up from the truck frame with the assistance of a helper. Set the longbox frame aside on the ground.
5Measure the distance between the front and rear bolt holes for the mounting bolts on the shortbox, using the tape measure. Measure up the side frame rails from the rear mounts. Mark the location on the frame for the front mounts, with the felt-tip marker.
6Remove the front mounts from the frame. Fabricate new front mounts on the frame by drilling holes for the mounting bolts. Place the shortbox on the frame, and align the mounting holes with the mounts on the frame. Insert bolts into the holes and tighten the nuts.
7Replace the small bolts that are used to secure the neck of the gas tank. Secure the bolts by tightening a nut on each bolt. Connect the wiring connector for the rear lights.
