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2010 Ford Mustang GT Currie Enterprises' 9-inch Axle Upgrade Kit - Bolt-In & Battle ReadyThe Weekend Warrior gets a stronger, firmer rear from Currie From the May, 2011 issue of 5.0 Mustang & Super Fords By Dale Amy
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Classic Design Concepts’ Weekend... Classic Design Concepts’ Weekend Warrior SEMA project is a ’10 GT that will spend much of its post-show life on the nation’s road courses, where the strength and gear-swap convenience of Currie Enterprises’ 9-inch axle upgrade kit will be put to good use. We’re lucky. For years, the factory has equipped the V-8 Mustang with an 8.8-inch rear axle assembly. It has earned a reputation for hardiness at power levels well beyond stockat least, in street applications, where traction usually breaks before the rearend housing. Even so, back when the 8.8 was engineered, it’s safe to assume that nobody on the project foresaw the day of 600, 700, or 800hp street Mustangs. Nor was the housing or its internal components designed with the high-traction torture of a dragstrip or the high-heat environment of a road-course in mind. Its integrated-carrier design also complicates gear ratio swaps. All of which is to say that like every stock component, the 8.8 axle simply has its limitations. But, as Blue Oval fans, we’ve always had an ace up our sleeve, in the form of Ford’s venerable 9-incharguably one of the sturdiest axle assemblies ever engineered. And strength isn’t the only advantage of the 9-inch design; there’s also that removable gear case, or third member, which permits relatively quick ratio or differential swaps for swift adjustment. Of course, the 9-inch axle housing itself is a rather generic beast, seeing use in everything from muscle cars to stock cars. Luckily, the aftermarket embraces the basic design, with companies like Currie Enterprises manufacturing application-specific versions. The centerpiece of the kit... The centerpiece of the kit is Currie’s 9-Plus Heavy Duty housing, a sturdy beast built to stock S197 width and pinion-offset specs. It is fitted with the company’s 31-spline axles, and all the necessary factory-style brackets are jig-mounted in place. One of Currie’s latest variants is a 9-inch upgrade kit specific to the S197 chassis, meaning it is correctly sized and configured to bolt right in place of a factory 8.8-inch assembly, while allowing retention of the factory rear brakes and even ABS function. More than just a housing, Currie’s unit is an overall upgrade kit complete with 31-spline axles, a one-piece aluminum driveshaft, Currectrac lower control arms, and an adjustable third link. That kit was just the ticket for a car like Classic Design Concepts’ Weekend Warrior projecta ’10 GT conceived for the 2009 SEMA show. Once its show duties are wrapped up, the Weekend Warrior will see street driving and open-track use at road courses around the country. Such an application will benefit greatly from both the greater strength and easier gear swaps of Currie’s 9-inch upgrade kit, which installs as a straight bolt-in replacement, as evidenced by our photos. Also in place are ABS reluctor... Also in place are ABS reluctor wheels, and the supplied caliper brackets are drilled and tapped for the factory ABS sensors. Your stock S197 disc brakes will bolt right on and full ABS function is preserved. You’ll sometimes hear of designs like the Mustang’s venerable factory 8.8-inch rear, with its integral gear carrier, referred to as a Salisbury-type axle (the name of an early manufacturer). Removable-carrier axles like the 9-inch are also often called banjo-style because, in someone’s mind, that’s what their empty housings resemble.  Also in place are ABS reluctor...  Also in place are ABS reluctor wheels, and the supplied caliper brackets are drilled and tapped for the factory ABS sensors. Your stock S197 disc brakes will bolt right on and full ABS function is preserved.  The sturdy upper control arm...  The sturdy upper control arm bracket is fitted with Currie’s Johnny Joint rod end. There are a multitude of options when it comes to configuring the third member. The one for Classic Design Concepts’ Weekend Warrior has a nodular case fitted with 3.89:1 gears and a Detroit TrueTrac gear diff.  Though you can, of course,...  Though you can, of course, order the housing on its own, Currie offers a complete upgrade kit, with one-piece aluminum driveshaft, Currectrac lower control arms, adjustable upper control arm, and a supply of 85W/140 gear oil.  The factory lower control...  The factory lower control arms are stamped steel and don’t inspire much confidence as to their rigidity. Currie’s Currectrac replacements are whittled from billet 6061-T6 aluminum. They feature greaseable rod ends at the (larger) axle end, and similarly greaseable spool-type urethane bushings at the other.  Currie’s upper control arm...  Currie’s upper control arm wears a heavy-duty fork at the housing end and a greaseable rod end where it bolts to the chassis bracket. They are pre-adjusted to factory (8.48-inch) length, but can be adjusted either on or off the car to precisely establish your desired pinion angle.  Our starting point is a bone-stock...  Our starting point is a bone-stock ’10 GT rearend (aside from the FRPP springs, which, you may notice, were installed upside down.) While the length and bracket hardware has evolved over the years, the basic 8.8-inch center section is essentially unchanged from the Fox era.  First to come out was the...  First to come out was the factory’s two-piece, jointed driveshaft. Naturally we were curious, so CDC boss George Huisman weighed it in comparison to the one-piece aluminum replacement. This stock shaft was about 25 pounds heavier.  Next out was the sway bar,...  Next out was the sway bar, but only because it was being upgraded at the same time. Normally, you could likely get away with just unbolting the bar ends from the axle’s shock brackets.  The Panhard bar was next....  The Panhard bar was next. Note that the ABS sensors are unbolted (and will be reused with the new axle.) Incidentally, this whole swap is a simple bolt-in replacement, which could be done in a driveway—with a chiropractor standing by. But it’s one of those deals where renting garage space with a hoist, jacks, and air tools might just be cheaper than the chiropractor.  The rear calipers are unbolted...  The rear calipers are unbolted from their axle brackets and hung out of the way. Also, the e-brake cables are unhooked from the brake assemblies.  With the axle supported, the...  With the axle supported, the lower shock bolts as well as the axle end of the third link are unbolted. All major factory suspension fasteners will be reused with the kit. At this point, only the lower control arms remain attached to the axle.  Once the two lower control...  Once the two lower control arms are unbolted at the axle end, the hoist is raised (or the axle assembly lowered). The lower arms can then be unbolted from the chassis. Some items will now have to be transferred over to the new 9-inch housing.  Here, the rubber coil spring...  Here, the rubber coil spring perches, the axle bump stops, and the caliper brackets’ backing plates have been installed on the Currie housing, which has been set on the jackstands, ready to be bolted up in place.  But first, the third link...  But first, the third link must be swapped out for the Currie piece, a task complicated by insufficient clearance to get the bolt out past the floorpan. The solution requires loosening the two link-bracket bolts visible here, and then going inside the car and under the rear seat to loosen a final fastener from up top. Only then can this crossbolt be removed and reinstalled on the new link.  Another small task deserves...  Another small task deserves mention. A Tab on the new axle's lower control arm brackets must be bent out to 45 degrees in order to provide clearance for the Currectrac arms. The tab can remain as shipped if you are retaining your stock control arms.  One final note. The new axle’s...  One final note. The new axle’s steel brake-caliper brackets are thinner than the cast-iron counterparts on the factory axle. The kit supplies spacers (arrows) so that the factory bolts can be used and still clear the rotors.  Otherwise, the new axle and...  Otherwise, the new axle and driveshaft simply bolt up in place of their factory counterpart. CDC also took the opportunity to upgrade the rear sway bar and dampers on its Weekend Warrior project with pieces from Ford Racing Performance Parts.  Here is another view from...  Here is another view from the front, showing the kit’s one-piece driveshaft installed. 5.0
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