How to Convert a Regular Truck to a Duallyby Russell Wood
Trucks are great for hauling heavy loads and they have lots of utility space for whatever you need to carry. But not all trucks are created equal. If your truck has dual rear wheels--commonly called a "dually"--you can pull heavier loads and carry more weight in the bed because of the extra strength that the dual rear wheels can carry. Thanks to mass-production techniques, you can turn your single-wheel axle truck into a dually with just a few parts and supplies.
Lift up the vehicle using the jack and place it on jack stands. Make sure the vehicle is secure before you crawl underneath it. Place stands underneath the axle and the frame. Remove the rear wheels using the tire iron and place them to the side.
Unbolt the four bolts that hold the driveline to the axle using an open-end wrench. Then place the 24-inch pry bar between the driveline and the axle, and use it to pry the driveline out of the axle.
Unbolt the brake line that runs from the frame to the axle using the brake line wrench set.
Unbolt the leaf springs from the vehicle using the 1/2-inch ratchet and socket set and open-end wrenches. There are two bolts at the front of the leaf spring, mounted to the frame, and another pair at the rear of the frame, near where the back bumper bolts to the frame. Unbolt the rear shocks from the frame and axle at this point as well using the 1/2-inch ratchet and sockets and an open-end wrench. By doing this, you will free the axle from the frame.
Slide the jack underneath the center of the axle, known as the pumpkin. Lift the axle off of the jacks, remove the jack stands, and then lower the axle down so that it sits directly on the jack. Then slide the jack backwards out from underneath the vehicle, with the leaf springs connected.
Mount the heavy-duty leaf springs to the frame using the 1/2-inch ratchet and socket set and an open-end wrench. These leaf springs will go in the same way as the stock units, with one mount up front on the frame, and one on the rear by the back bumper.
Slide the dually axle under the vehicle by placing it onto the jack, then pushing the jack under the vehicle. Lift up the axle using the jack and secure the axle on jack stands. You may want to have an assistant help you locate the axle in the frame because of its weight. This dually axle can be found at a junkyard or through your local dealership, depending on how much you're willing to pay. If you buy a junkyard model, make sure that there are no obvious leaks near the differential cover or at the ends of the axle by the axle seals, and check the drum shoes or disc pads to make sure they are in good working condition. If not, you can always replace the brakes, but it's easiest to start with something that works well to begin with.
Unbolt the u-bolts that secure the axle to the leaf spring on the old axle using the 1/2-inch ratchet and socket set. Then transfer those u-bolts to the new axle, and secure the dually axle to the leaf springs, orienting the u-bolts and leaf spring in the same way as they were on the stock axle. There is a pin in the center of the leaf spring that will line up with a hole in the axle pad on the axle. Make sure the two of them line up as you tighten the u-bolts to the axle using the 1/2-inch ratchet and socket set.
Connect the driveline to the axle by placing the u-joint of the driveline into the yoke of the axle and connecting the straps to the axle using an open-end wrench and the bolts on the axle. Then connect the brake line from the axle to the frame using the brake line wrench set.
Have an assistant climb into the vehicle and press down on the brake. Locate the brake bleed screw on the back of the drum or brake caliper, and open it up using an open-end wrench. You want to get a steady stream of brake fluid out of the bleeder screw. Open the screw when your assistant pushes on the brake, and close it when he stops. It should sputter a bit and spit out air. Once it spills out clear fluid, close the screw and repeat the process on the other side of the axle. Open the hood and fill the master cylinder with brake fluid until you've reached the fill level.
Bolt the dually wheels to the axle using the tire iron. Lift the vehicle off of the jack stands using the jack and place it onto the ground.