The Yukon mini spool for Ford 9-inch with 31-spline axles installs into a standard open carrier and supplies continuous 100% traction to both wheels by replacing the spider gears. Intended as a low-cost traction option, these spools are best for non-street applications; Yukon recommends full spools for extreme tire sizes or high-power drivetrains.
Yukon Gear Mini Spool For Ford 9in w/ 31 Spline Axles