When the Ford 9-inch axle originally appeared in 1957 under the Fairlane and F-100 pickup truck, no one knew what an enduring legacy it would have. To put that in perspective, the top-of-the-line Fairlane used four-wheel drum brakes and manual steering, and made 245 hp from the carbureted FE engine. You wouldn’t swap any of those parts under your 4x4 today, but the 9-inch still enjoys incredible popularity. In fact, despite being discontinued by Ford in 1986 in favor of the 8.8 axle, there are more 9-inch parts on the market now than ever before.
We spoke to Brian Shephard, marketing director at Currie Enterprises, to get the lowdown on what makes the 9-inch so popular. While Currie offers everything from 12 Bolt to Dana 70 axles for 4x4s and hot rods, the 9-inch has been the company’s bread and butter for decades. In fact, these days, you can only order up a 9-inch from Currie that is built entirely from new parts. Conversely, you can pull a Ford 9-inch out of a truck in a junkyard and swap it under your rig for a couple hundred dollars. Most people mix and match new and used parts to get the most bang for the buck.
There are several reasons the 9-inch enjoys such a strong following. The removable third member makes gear changes much easier than Salisbury-style (Dana) axles. The use of a removable pinion support and spanners instead of carrier shims makes gear setup easy. And there are a nearly infinite number of gear ratios available for the 9-inch, from as high as 3.00 and as low as 6.50. The removable third member also means that the sheetmetal housing is not only lighter than a comparable Dana axle but is easier to weld brackets to for your link suspension since you do not have to contend with a cast centersection.
The gear design itself is responsible for the 9-inch’s reputation for holding up to high horsepower. While the ring gear diameter is smaller than a Dana 60, pinion offset from the centerline is 2 1/4 inches for a 9-inch and 1 1/8 inches for a Dana 60. This is a tradeoff, because the Dana 60 will provide a better driveline angle and more ground clearance beneath the yoke, but the Ford 9-inch will have better tooth engagement between the ring gear and pinion due to the angle of the teeth on the 9-inch design. And like a Corporate 14-bolt axle, the 9-inch has a third pinion bearing beyond the pinion teeth that minimizes gear deflection.
All of this adds up to an axle that has endured for more than half a century and shows no signs of fading into obscurity any time soon.
Ford 9-Inch Advantages
• Removable third member
• Third pinion bearing
• Pinion offset
• Sheetmetal housing
• Strong aftermarket support
Ford 9-Inch Axle Widths (in)
• 1965-66 Mustang, 57.575 inches
• 1966-77 Bronco, 58 inches
• 1978-86 Bronco, 65 inches
• 1974-86 F-150, 65 inches
• 1972 E250 Van, 68 inches
Ford used a variety of housings over the years, and Currie offers all of them as upgraded reproductions, as well as housings of their own design. The earliest housings used in cars through the mid-1960s were the weakest, with abruptly ending butt-welded carrier centers to tubes and a smooth backside. Later housings appeared in 1966 with stronger tubes and the familiar “hump” in the middle of the housing. The later truck housings received even beefier center housings that extend farther into the tubes for more strength.