Donald Farr
Former Editor, Mustang Monthly
October 1, 2009

Remember the days of scrounging junkyards in search of a 9-inch rearend to replace the wimpy 8-inch in your high-horsepower vintage Mustang? Whether you were looking to beef-up the strength for hard launches or you desired a higher (numerically) gear ratio, the 9-inch from an old Galaxie, truck, or - if you were lucky - a high-performance Mustang got you both strength and, more than likely, a digger gear. Today, it's virtually impossible to find an old 9-inch in the junkyard.

That's one reason that John's Industries, home of The 9-inch Factory, offers a bolt-in Sport 9-inch rearend for '65-'73 Mustangs and other vintage cars. With brand-new housings made from The 9-inch Factory's own tooling, the rearend assembly comes with your choice of Motive ring-and-pinion gears in a lightweight nodular case, Traction-Lok differential, OEM 28- or 31-spline axles, and big-bearing, late Torino-style flanges. To help with the swap, the housing is also fitted with spring perches, brackets and tabs, new pinion yoke, axle seals, studs, fasteners, and housing vent. Available options include 10x21/2-inch drum brakes, aluminum third member, pre-bent brake lines, and disc brakes from either Ford Racing or Stainless Steel Brakes Corporation.

With prices starting at just under $3,000 retail for a unit with drum brakes, the bolt-in 9-inch rears aren't cheap. And the price goes higher when you add disc brakes, powder coating, and other options. However, when you look at it as a complete, ready-to-swap assembly that provides better brakes, a beefier housing, and Traction-Lok gears of your choice, it's a pretty good deal compared to locating a suitable vintage 9-inch and adding all the components yourself.

The 9-inch factory sent us a bolt-in Sport 9-inch for Classic Creations of Central Florida customer Brett Butler, who was looking for a 9-inch and gear ratio upgrade to replace his '65 Mustang fastback's original 8-inch, which was leaking fluid and whining at highway speeds. Merv Rego and Matt Simmons, with help from Brett, made the rearend swap in an afternoon, with only a couple of modifications required - a different universal joint to mate to Brett's driveshaft and some minor grinding to open up the spring perch positioning hole for Brett's lowering blocks. Wider u-bolts and shock/spring mounts from '67-'70 Mustangs are also required.

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