5.0 Mustang & Super FordsHow To Drivetrain
Fox Mustang Rearend - Short And Stout
Strange Engineering Chops, Cuts, And Builds A Stout 8.8 For The Fox 500
Horse Sense: Editor Steve Turner has high hopes for getting the massive 18-inch wheels and tires of an '07 Shelby GT 500 to look as though they belong on his Fox-body version of the super 'Stang-without putting a hammer to the wheelwells. [But thanks to KJ's tire-sizing recommendations, there's not much chance of that!-Ed.]
5.0 Mustang & Super Fords Editor Steve Turner is now in full swing with his project 'Stang: the '88 T-top LX you've been reading about in our magazine. You also may have seen discussions about the rare car in 'Stang-themed message forums on the Internet.
With Ford Racing Performance Parts' Condor (PN M-6007-C54; $15,999)-a 500hp supercharged 5.4 crate engine-and Tremec's custom TR-6060-in-a-T56-case six-speed leading the lineup of cool components in Fox 500's drivetrain, any performance aficionado could argue that installing a 9-inch rearend is the only way to properly close the drivetrain for Steve's radical 'Stang.
Ford's beefy 9-inch is considered by most gearheads to be the ultimate in rearend options. While the rear's fame comes primarily from its success on the race track, we've also seen a fair amount of 9-inch setups under street Mustangs that pack a lot more power and torque than one might think. Fox 500's project-car brother (our '86 T-top coupe) fits this mean street-'Stang description; it relies on a Strange Engineering, Motive Gear, and Eaton Detroit-stuffed (axles, 4.30 gears, and Locker differential) FAB9 rearend to handle all the muscle its supercharged powerplant can flex.
Steve has opted to install an 8.8 rearend below his radical new ride. The decision was made mainly because an 8.8 is much lighter than a 9-inch, and Steve's overall plan with Fox 500 is to do a lot less dragging-if any at all-than simply driving the blown, mod-powered, '88 T-top car on the highways and byways of the Sunshine State. That, and his suspension from Maximum Motorsports requires an 8.8 for its torque-arm arrangement, which will plant all that GT 500 power. Despite the "ultimate-rear" cred the 9-inch carries, the truth of the matter is a Mustang's 8.8 rearend can be just as great, provided it's built with the right parts and set up by a technician who knows what he's doing.
Strange Engineering's JC Cascio promised the company's technicians would ensure the car's rear is correct by assembling the killer 8.8 being featured in this report. The rear is highlighted by a pair of Strange's street-tough, 31-spline, S/S Street series axles (PN P3102; $369.60) and its chrome-moly 9-inch housing ends (PN H1138; $70.00). They were fitted into and on FRPP's 8.8 rearend housing (PN M-4006-C373, $875.00).
Of course, no rearend would be considered complete without gears and a diff, so Strange also outfitted Steve's housing with a 3.73 ring-and-pinion gearset from Motive Gear (PN F888373; $158.00) and an Eaton Detroit TrueTrac (PN 913A561; $435.95) locking differential.
Paul Svinicki of Paul's High Performance in Jacksonville, Michigan, is the shop that has taken on the challenge of turning Steve's Shelby GT 500-powered dream into a real-deal Fox 'Stang. It's a daunting task, but the project seems to be moving along nicely. The T-top LX's complete Maximum Motorsports front suspension is now in the car ("Supporting Cast," Oct. '07, p. 56), and once the Strange-built rear arrives at Paul's and is combined with Maximum's gear for the backside, there's no doubt the ponies running through the FRPP aluminum driveshaft will find their way to the pavement when Steve takes the wheel and finesses the gas pedal.
Rearend assembly is actually a twice-done process. A rear is usually mock-assembled for measurement taking and fitment analysis, which helps an assembler determine correct shim sizes and clearances, among other things.
The following photos capture some of the highlights of Strange Engineering's 8.8 build for Fox 500.
Each axle tube is carefully measured. Per Paul Svinicki's instructions, 2 inches (measured along the axle tube from the back of the stock bearing housing to the differential housing) are sliced from each tube.A chop saw handles this task nicely. Strange's tech-nicians remember to accommodate the thickness of the housing ends that will be welded on, as well as axle length.
Once the sawed-off ends on each axle tube are deburred and cleaned, our Strange 9-inch bearing housings (housing ends) are set up for welding on a bar-style, installation jig. The jig is a dual-purpose tool, as it also serves as a truing index for straightening axle tubes as they're being welded to the differential housing.
The 9-inch bearing housings...
...are TIG-welded into place.
Fox 500's rearend housing is ready to go through the remainder of its assembly. Our new 9-inch ends will hold bigger diameter, self-contained bearings, offering better containment for the axles and are less prone to leaking or failure.
Bench, or out-of-the-car rearend builds similar to ours are best done with the housing laid across a large barrel.
Due to the uniqueness of Steve's drivetrain plan, Strange's techs removed the prepackaged FRPP equipment and prepped the bare housing for installation of the heavier-duty Eaton Detroit Truetrac differential and its supporting cast of Motive Gears and Strange axles. The 8.8 rear is shipped in just-add-axles-and-brakes trim with a 31-tooth Traction-Lok differential and 3.73 gears already installed-a great setup for those who want to swap out a 7.5-inch Mustang rear or are stepping up their 'Stang's performance program. Prior to assembly, the entire works receives a good cleaning to clear out metal or other debris that can cause damage to the gears, axles, differential, and other parts.
This Eaton Detroit Truetrac differential is a big part of the rearend combo. Steve decided to go with this gear-driven, limited-slip posi unit over the full-time lockup of a locker or spool, mainly because Fox 500 will be driven in a similar manner as the S197 super 'Stang from which the T-top project gets its name. For Mustangs that are cruised more than they're raced, a TrueTrac is a good choice because it's a differential that manages torque much better than a factory unit can and will lock up only in the event of wheelspin or other sense of lost traction.
Strange's techs true-up ring gear/differential alignment using the ring-gear bolts, and then press the gear down onto the diff. Red Loctite is used to ensure the bolts stay down once they're torqued.
The carrier bearings are then positioned and pressed onto both ends of the TrueTrac. Stub axles are inserted through the differential, which is held by a bench vise and a wrench. The ring gear bolts are torqued to 70 lb-ft.
The front-bearing area is visited twice during assembly of our 8.8 rearend. The first time, a setup front bearing, similar to the one shown in this photo, is placed inside the diff housing and stays there while the clearances for the differential and gears are dialed in. The rear is mock-assembled and taken apart before the axles are installed.
After the rear's mock assembly and the correct front bearing is in place, a seal is tapped down into the housing with a bearing race. Strange's technicians apply a thin bead of RTV to the seal for extra insurance against shifting or popping out of the housing. All the bearings and seals used for the axles are included with Strange's 31-spline pieces, and similar hardware for our 3.73 gears and TrueTrac diff are included in Motive Gear's Master Installation Kit (PN R88RMKT; $94) axle kit.
The pinion gear is inserted into the differential housing and secured. Note that the crush sleeve is in place on the pinion shaft. A small bead of thread sealer is added to the pinion's threads prior to setting it in place.
Installing the pinion flange is next, and then an inch-pound torque wrench is used to tighten the pinion nut until there's only 0.025-0.030 lb/in of drag.
Our Eaton Detroit TrueTrac differential and 3.73 gears are set into position. This process takes time and patience, because the assembly requires trial-fitting side shims of varying thickness before it can be final-installed. Main caps must be installed in the same position from which they were removed at the outset of the build, and each main-cap bolt gets 70 lb-ft of torque. It's hard not to notice the gearset's bright shine. The ring-and-pinion received a Mikronite treatment for improved durability and impact resistance. The finish will reduce friction, resistance, and corrosion.
Backlash and ring-gear preload are checked in three places on the ring gear, using a dial indicator. If backlash is less than the lowest acceptable value (0.008) or greater than the highest (0.010), the side shims will be added or removed from either side of the carrier in order to achieve the proper spacing between the ring-and-pinion.
Several teeth on opposite sides of the ring gear are painted with gear-marking compound. When the differential is rotated with the pinion yoke, the drive side of each tooth should have a centralized pattern that slightly favors the inner end of the tooth.
Before inserting the axles, North Racecars' brake-caliper mounting plates are secured to the rearend housing with 35 lb-ft of torque applied to its 3/8-inch bolts. After pressing bearings and wedding bands onto each axle, they're positioned in the rear until the splines are properly seated inside the TrueTrac differential. Due to the fact our rearend has 9-inch housing ends, the locker's axle spacer isn't necessary and the Strange technician blocks off the unit's internals with a supplied cover and snap ring.
Standard-length, 1/2-inch wheel studs are driven into the project's 31-spline Strange S/S street axles. Red Loctite is added on all the bolts prior to tightening them at 85 lb-ft of torque.
FRPP's low-profile, aluminum differential cover (PN M-4033-G2; $199) closes out Fox 500's new rearend. A gasket is supplied and a bead of RTV also ensures there will be a leak-free seal between the cover, the differential housing, and the gasket. Fasteners for this cover receive 25 lb-ft of torque, and once the cover's support jackscrews are properly positioned against the main caps inside the housing, each jam nut is torqued with 50 lb-ft.