The USA Standard Mini Spool for Ford 9" with 31-spline axles installs into the open carrier in place of spider gears to provide full-time lockup and consistent traction. As a low-cost traction option, the mini spool delivers 100% power to both wheels but is not recommended for street-driven vehicles. It fits Ford 9" housings with 31-spline axle setups for dedicated off-road or racing use.
USA Standard Mini Spool For Ford 9in w/ 31 Spline Axles