When building a custom car or truck, sometimes you want to run a wider wheel in the back and you don't have the room to do it. One easy way to do it is to narrow the rear end, which gives you extra room for rims. Doing this can be challenging, and requires extra work, but the end result is worth it. This project vehicle is an axle from a 2001 Chevrolet Silverado, but the process is similar for other vehicles.
Jack up the axle and place it on jack stands.
Unbolt the brake calipers from the axle using the 3/8-inch ratchet and socket set.
Slide the rotors off of the rear end using your hands and set them to the side.
Unbolt the differential cover using the 3/8-inch ratchet. The differential fluid will drain out at some point so have the drain pan ready.
Unbolt the bolt that holds onto the locking pin on the axle using the 3/8-inch ratchet. The locking pin will then slide out of the differential, so place it to the side.
Push in the end of the axles and pull the c-clips out of the axle ends at the differential. At this point, the axle shafts are free and can be pulled out of the housing. Take the shaft out as straight as possible so that you don't screw up the axle seals.
Mark the axle the amount you want to narrow the axle using the permanent marker. Typically, you want your cuts to be inboard of the leaf spring mounts, but not directly at the differential. Place a straight edge on the top of the axle and mark a line across the top of the axle using the marker. This will be an alignment point for the cut so that you make sure the axle stubs don't twist in the process.
Place the axle on the chop saw and make sure that the axle is at a 90-degree angle to the cutting blade. This step is critical, so be sure you've got it set up correctly.
Cut the axle using the chop saw. Cut it in both places where you marked it using the chop saw.
Grind a 45-degree angle into the axle housing and the cut off ends. What you're doing is making it so that when you push the two pieces together, it forms a "V" shape with the bottom of the V points towards the center of the axle. This is going to give you a good spot to weld to.
Hold the axle stub to the axle housing using your hands and align the horizontal mark you made in step 7 so that the two marks line up.
Tack weld the axle together using the MIG welder. A tack weld is a temporary weld that doesn't require a lot of welding time and isn't a full bead. In this case, you'll pull the trigger for maybe two seconds, giving a thick weld to the axle. Do this around the outside of the axle in four places.
Hold the straight edge on the axle to ensure that it's perfectly straight. If the axle is twisted or tilted one way or another, you'll go through axle seals and have vibration issues.
Weld the axle using short beads, 2 inches long at a time. Rotate the axle and weld one section, then weld another on the opposite side, so as not to build up heat.
Place the axle shafts in a box and send them off to a machine shop to be shortened. The axle shafts have machined ends that can't just be cut and welded together---they have to be machined.
Reassemble the axle once the axle shafts come back from machining in the reverse order of disassembly.
