K.J. Jones
February 6, 2007

Put yourself in this scenario: Suppose you've spent the better part of two weeks building and installing a fresh, new, big-horsepower stroker engine and adding a nitrous system under the hood of your otherwise stock 'Stang-and those are the only things you've done. You're ready to show it off to a few of your closest friends at the local 1,320 in what you've been billing as your car's "arrival" from 13-second beater to 10-second hitter, thanks to the power surge you've created.

It would be wonderful if such a story had a happy ending, but the reality is it usually doesn't. In this hypothetical case, a quick check of your mirrors during the burnout reveals that the passenger-side rear tire is the only one churning smoke skyward. That can't be right . . . right?

No, it isn't right. While the one-legger burnout should be a signal that something is amiss with the 5.0's rearend, drivers usually proceed to the line with tire-yanking expectations, only to have their dream die the instant the clutch is dumped and a tire hooks when horsepower and torque seek out the weakest link in the drivetrain, which is usually that stock 8.8 rearend.

Power and torque can cause three different types of problems in a 'Stang's rearend: broken gears, a broken or "exploded" differential, or-the granddaddy of 'em all-twisted 28-spline axleshafts that will eventually break.

We've seen all kinds of breakage firsthand and want to inform you about a relatively economical way to build a rear that will stand up to the same forces of power and torque, and more that could pretzel your stock equipment.

The axles and rearend housing are at the core of any good, strong 8.8 build. Thicker and hardened pegs make a huge difference in the amount of power you can get to the rear wheels and, ultimately, the ground. Reinforcing the rearend's outer structure is important for a 'Stang's overall chassis dynamics, as well as for hooking and booking.

We're presenting what we call a "bench build" of a stout 8.8 rearend, as we're going beyond the comfy confines of simply changing a set of gears, while the rearend is still on the car. Using a core housing, we'll show you how a rearend is straightened, welded, and upgraded with bigger axle-bearing housings-the same size that are on Ford's fabled 9-inch rearend. This has long been recognized as Ford's strongest factory rearend assembly that's popular in drag racing.

Many World Ford Challenge regulars are familiar with the name "Robert V." Robert heads up the WFC Tech staff and is among the few cats who can honestly be called a hard-core 'Stangbanger on the West Coast. With plenty of 8.8 builds of this nature on his resume, Robert is a perfect teacher for this exercise and we thank him for helping and showing us how to get it done properly.

Horse Sense: Know the limitations of your equipment! Thanks to hot crate engines, bolt-on performance parts such as heads, cams, and power adders, 400-plus street horsepower is near the norm these days for 5.0 'Stangs. So you're only fooling yourself if you think the high-mile, OEM rear under your stout ride will last forever. Trust us-it's not gonna happen.

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Any rearend build that involves cutting axle tubes and welding on the rearend-housing ends, axle tubes, and such-is more extensive than a standard gear/axle swap. While we wholeheartedly support a do-it-yourself initiative, this job is better left in the hands of someone with experience. Our good friend Robert V has performed this operation countless times and was kind enough to show how it's done. For starters, never try to pull this off with the rear still on the car. It's doable, but not advised. Supporting the rearend across a tall, steel trash can or barrel makes it easy to maneuver into many different positions that are necessary for measuring, cutting, welding, and installing.
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The first order of business is to unbolt and remove the rearend housing if you're using your 'Stang's original rear, and to prep it for the upgrades. Since stepping up to Strange Engineering's 9-inch housing ends is a big part of this exercise and the axle tubes will be cut and welded on, it's important to get the complete housing as clean as possible. Our project rear is a little rusty and dirty because it's been sitting outside in the elements for several months
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Use a sandblaster, an air sander, a wire brush, several cans of brake cleaner, and an air nozzle to clean up all of the areas that will be welded on, as well as the axle tubes and differential housing. These are critical internal areas that must be free of any debris when you're building a rearend. We'll give our rear a fresh, new look with some paint as well, so taking it down to bare metal is necessary for a clean finish.
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Since we're installing spherical bushings for the rear upper control arms, the stock rubber bushings have to go. These press-fit bushings are sometimes difficult to extract. We sprayed a small shot of Royal Purple's Maxfilm penetrating lubricant on our bushings, then used an air hammer with a chisel-style bit to push each one out.
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If you go at this project on your own, measure a lot. Check and double-check your measurements. Cutting the axle tubes for the addition of big-bearing housing ends is not a hack-anywhere deal. Robert V measures the length from the start of the axle bores on the inside of the differential housing to the backs of the housing end on each tube. It's important to take measurements and calculate the actual amount that each axle tube must be shortened before the stock ends can be removed to make way for the big-bearing ends.
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Note that the driver-side tube is shorter than the passenger-side's to compensate for the offset created by the ring, pinion, and differential assembly, as well as an offset that's built into the car. Even though we're setting up our rearend to be a direct replacement, the axle tubes must be cut to accommodate the 3.10-inch thickness of the larger-diameter housing ends, as well as the length of each axle. It all has to work as a system-if you blow it, you'll be making the scrap-metal man's day.
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Secure the axle tube in a chop saw and cut off the stock housing ends. Once they've been removed, use a disc sander to clean up the residual metal on each end.
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This apparatus is used as an index for checking the straightness of the axle tubes and for positioning the 9-inch housing ends for additional measuring. It's also used for keeping the ends centered and seated on the tubes when Robert welds them in place.