The earliest 9-inch housing is identified by its two dimples, fill plug, and round shape without much triangulation from the centersection down to the axle tubes. Ford built these housings with the tubes butt-welded to the centersection, which is not very strong. |
The next phase of design was very similar with the dimples and fill plug, but theres more support of the axle tubes thanks to a longer transition to the tubes to provide triangulation. These are among the most common housings, and many shops use them when making custom setups. |
Around 1977, Ford introduced a second version of the triangulated housing for use in Broncos and 1/2-ton trucks; its easily identified by the different shape of the rear of the pumpkin. This is the housing most likely to come stock with the preferable large-bearing axle-tube ends, but the aftermarket can also supply weld-on tube ends, so its not that big of a deal. |
Many shops upgrade the strength of the housing by increasing the diameter of the tubes. This Currie Extra-Heavy-Duty setup is an early triangular housing thats been modified with 31/4-inch-diameter, 0.250-wall seamless tubes that are pressed into the centersection a full 7 inches before being welded. For most street/strip cars, the increased strength more than makes up for the added weight. |
Finally, for really heavy or really fast street cars, Currie offers the Extreme-Duty housing with both the large axle tubes and an extra brace across the back. Also note the weld-on oil-fill bung at the top. |
Ford 9-inch rearends are ubiquitous in the world of gearheads. Even a Chevy guy could probably tell you that the 9-inch was introduced in 1957 and that the dropout-centersection design, high-hypoid gear cut, and pinion-nose bearing make it a convenient and sturdy rearend. Those are some of the reasons why car crafters with all makes of vehicles have swapped 9-inches into their cars with help from one of many shops that'll build the Ford diff in any configuration you need. But with over 40 years of stock variants and aftermarket upgrades available, it pays to know what youre getting into when buying or upgrading a 9-inch.
That's what this story is here for. Our friends at Currie Enterprises were among the first to offer custom 9-inch diffs, and while they now handle Danas and GM 12-bolts as well, they're considered among the most knowledgeable 9-inch tuners out there. In addition to sourcing infor-mation from the catalogs of many manufacturers, we toured the Currie shop and picked their brains to provide this overview of the most common 9-inch pieces you'll have to choose from for the typical serious streeter.