Out back is a huge Meritor RS-17-145 axle that’s rated at 17,000 pounds. It has 2-inch-diameter, 39-spline axleshafts and a ring gear diameter of 15 inches. Like the front axle it sports 5.13:1 ratio gearing. Chucks Trucks lifted the suspension using longer, custom-fabbed, factory-like hangers, six 1/2-inch-thick factory-like custom laser-cut shims (per side), longer U-bolts, and tractor-trailer supply house-sourced longer shocks. This increased suspension height provides room for a set of 54.5x24.0R21 Michelin XZL tires. The tires are mounted on custom split-rim steel wheels that are 18 inches wide.