The Ford 9-inch rear axle assembly is the gold standard for a solid rear axle in the eyes of many a builder and enthusiast. Among all of the 9-inch's positive traits, the removeable center section, or case, is a big plus. With minimal work, the center section can be removed from the axle housing for whatever need you may have. Want to inspect the condition of the limited-slip unit? Want to change up the rear gear ratio? In both cases, having a 9-inch makes that job so much easier than, say, a GM 12-bolt. The strength of the 9-inch center section is part of the axle's overall bulletproof reputation, either in stock or aftermarket forms. GearFX offers three different case styles for 9-inch Ford axle builds: the N-series, the S-series, and the HS-series. They all have their advantages and disadvantages, but which case is right for your application?