Tim Stockwell
January 23, 2006
Tim Stockwell burns the back tires into globs of molten rubber on our new project '99 GT. With a little effort, we'll show you how to turn a '99-'04 GT into a serious straight-line threat. This month, we're starting at the back and working our way forward.

Horse Sense: The used car market is littered with '99-'04 Mustang GTs in excellent condition. While the aftermarket was only lukewarm when the cars debuted, it is now white hot with performance equipment that can transform one of these cars into a serious street machine. You can find a nice GT-like our test car used for this story-for under $12,000.

In our December '04 issue, we introduced you to Tim Stockwell and his insanely stock 10-second street 5.0 LX ("Stock Exchange," p. 64). Since then, Tim has helped us with a couple of technical articles and, most recently, he invited us to tag along as he transformed his newly acquired '99 GT into the next Stockwell project Mustang. In case you're wondering, the white LX coupe was sold to fund the purchase of an '03 Cobra, which was itself sold. So, Tim continues to update cars and move on to the next project. We are hoping to document a full-and trick-drag suspension on this '99, and perhaps put a turbo kit on the engine to see how a 4.6 Two-Valve likes a hairdryer. For our first dance with this GT, Tim suggested we check out his standard 8.8-inch rearend buildup. We couldn't resist.

Here is the stock 8.8-inch Ford rearend as pulled from a '99 GT. It is about to be straightened, narrowed, welded, and rebuilt.

The '99-'04 GT Mustangs are hot members of the Mustang universe right now. These low-mileage cars are being sold by their original or second owners. They have also survived the test of time better than the '87-'93 5.0 Mustangs, so you have a better starting point. They're super-solid, and the aftermarket industry has finally gotten a handle on the 4.6 twice-cammed V-8. While we dog the modular family for having fragile bottom ends (the obvious exception being the bulletproof '03-'04 Cobra motors), these things make upwards of 500 rwhp with a power adder and careful tuning.

With any street/strip car, make sure the supporting equipment (fuel system, exhaust, suspension, and such) is in place before you make outrageous power, or you'll be kidding yourself on the starting line. Tim's '99 GT came with a automatic transmission, a Bullitt intake, some exhaust pieces, and 4.10 gears. Surprisingly quick from the get-go, the yellow screamer ran 13.70s after he put his super tune to it. Tim has always been a big proponent of getting a car's stance and suspension right before pouring in the power, so he outlined a plan that would have the GT down in the weeds with a little more room under the quarter-panels for some bigger street tires. We'll detail the killer stance of this car-and how to build a drag suspension for your '99-'04 GT-in an upcoming issue. But, for now, we're going to start at the rear of the car to get it ready to handle a bit more oats from the small-block Ford up front.

Our 8.8-inch rear is dropped off at Pro Street Chassis where owner Al Morgan goes to work. The rear is held in place on the Pro Street Chassis jig with a four-bolt fixture, which ensures the housing is straight and centered. Al uses a band saw to lop off 2.5 inches of axle tube from each end. Remember, those cuts must be perfectly straight and perpendicular to the axles, or you'll have all sorts of fun when you put it back together.

Our pictures detail the transformation that took place once Tim wrestled the 8.8 from under the car. He wanted the rearend straightened, the axle tubes welded to the rearend, and each tube narrowed to accommodate a bigger tire. Through the development of the modular Mustangs, Ford continued to widen the rearend to increase the footprint and fill out the growing quarter-panels. This makes the Mustang a great-handling car, but it can be tough when a hot-rodder wants to install aftermarket rims because the required backspacing isn't available. Further complicating matters is the use of the ABS system. Again, this is a great feature on the Mustang, but it presents problems when you start building the rearend.

We wanted to install 15x10 Weld rims with 5.5-inch backspacing. The rim is big enough to run a 325/50 tire, but Tim prefers the 275/60 that's stretched a little on this rim, giving the look of a smaller tire but with a nice contact patch. To fit this tire on a '99-'04 GT, the axle tubes need to be cut 2.5 inches on each side. Any narrower, and you'll run into some serious work-such as replacing the brake system and backing plates hitting the inner fenders. At 2.5 inches, you'll remove the quad shock bracket, which isn't a big deal for most folks. In this application-because we are going to show you how to safely lower one of these cars-we removed the shock mounting bracket and positioned it down and inward on the axle tube to clear the emergency brake bracket. As it turns out, the shocks are arranged in a straight up-and-down pattern, which should allow them to perform better.

Al welds the tubes to the centersection. Instead of being pressed into the centersection, the welded tubes greatly enhance the strength of your 8.8. You can see why it's important to have a jig that holds the tubes straight to the housing. Once they're welded into place, it isn't fun going back. Al uses machined fixtures in place of where the bearings would go, and slides a solid-steel, 1.625-inch jig bar through to ensure everything stays inline during the process.

While Tim handled the removal of the rearend, disassembly of the housing, and reassembly of the 8.8, all of the welding and cutting was done by Pro Street Chassis (Norton, Ohio). Al Morgan, the owner, has been a certified welder since 1964, and he's no stranger to the hot-rod marketplace. As you'll see in our photos, Al has even built special jigs and fixtures for this type of work on the 8.8 Ford rear just to accommodate Tim and his work on the 8.8-inch rear-axle assemblies. If you weld the axle tubes to the center of the housing without a good jig bar and tight fixtures, the heat will warp the tubes, and these housings aren't usually straight from Ford. With the axle housing, you want everything perfectly straight and centered. If not, you'll have a nice-looking Mustang that goes down the street crooked and wears out bearings and other parts quickly.

As you have probably guessed, Tim likes to save money when he can. He gets more out of stock Mustangs than anyone else in the country (remember, he went 10.60s with a completely stock-motored 5.0), and he does it cheaply. We have tapped into that philosophy with this newest project car. From out of the car to back in, Tim has a narrowed, straightened, and completely rebuilt 8.8 rear for little money. In addition to the housing, you'll have to spend money on axles ($239), bearing/seals ($120), 31-spline centersection ($75 for a used Ford truck Traction-Lok), ABS ring ($40), ring and pinion ($189), rearend lubricant ($30), and labor for the housing modifications ($250).

We encourage you to try this at home, but if you want to ship your 8.8 housing and all the parts to Tim [www.5litermustang.com], he'll do the work, assemble everything, and send it back to you for under $1,000, depending on options like powdercoating, shock bracket install, etc. That price includes a welded, straightened, and shortened rearend.

Next time, we'll show you what Tim's car looks like with the narrowed rear end, a trick drag suspension, and dropped to the floor. After that, we'd like to add one of the trick new turbocharger systems on the market right now. If you have a better idea, write us a quick e-mail. We'll put Tim to work on it!