The 2-inch-diameter, 0.250-wall Synergy inner axle sleeve doubles the wall thickness of the factory axletubes. By welding the two tubes together in multiple places, you get nearly a 60 percent increase in strength. On an old axle, you may have to use an engine cylinder ball hone to remove the rust and scale from inside the axletubes before installing the new inner sleeves. Make sure you remove all of the debris from drilling. You’ll probably need to use a plastic dead-blow hammer to get the sleeves to seat all the way against the outer edge of the original tubes.