1993 Big Block Ford Mustang - Brace Yourself - PHR Project Car

With the limited street duty Project Fox will see, we passed on the complexity, expense, and weight penalty of a limited-slip or locker differential and went with a spool instead. This Strange Pro Race steel piece weighs just 8.45 pounds, and is backed by a lifetime warranty.

While not quite as diverse as the 9-inch rearend's dizzying array of rear gear options, the 8.8 still offers plenty of ratios. With projected quarter-mile trap speed in the 140-145 mph range, our 8.8 was fitted with a 3.90:1 ring-and-pinion set, which will put our 532 big-block just past its 6,500-rpm power peak while crossing the traps in high gear on 28-inch tires. The Mustang rearend's oddball flat-flange pinion yoke was replaced with a more conventional 1350-series unit.

The aluminum differential support cover not only looks trick, it also features two integrated load bolts that add preload to the main caps. This additional support reduces gear deflection, stabilizes backlash, and minimizes the potential for cap breakage. Speaking of main caps, these billet aluminum units are lighter and far stronger than the cast factory pieces.

Keeping the tech inspectors happy at the track mandates 3-inch-long wheel studs. These 1/2-inch studs are plenty stout for our intended use, and are included as part of Strange's axle packages. With the axles clamped by a vise, Bill applied some red Loctite to the threads before cinching them down.

The C-clip eliminators-shown here after they have been pressed onto the axles-are essentially safety hub assemblies with integrated bearings that prevent the wheels from ejecting outward in the event of axle failure. The axles are locked into place by steel retaining rings.

While they can be installed on the axles using a hydraulic press, Bill prefers to first heat the retaining rings up with a torch before sliding them on. Since heated metal contracts beyond its original state as it cools, using this technique makes the retaining rings clamp more tightly to the axle than by simply pressing them on.

Before dropping the spool into the differential housing, new bearings were installed on a press. To prevent damaging the new bearings, Bill wedged an old bearing between it and the press piston. Since both bearings are identical in diameter, the likelihood of gouging or scuffing the new bearing is greatly reduced.

Whenever using brand-new components, tolerances can be very tight. Instead of beating the ring gear onto the spool with a mallet, the preferred method is to slowly cinch down on the ring gear bolts. Once the ring gear was seated, Bill backed off on the bolts a few threads, applied some red Loctite, and torqued them down to 80 lb-ft.

The final step before setting up the rear gears was installing the pinion bearing race in the differential housing. The procedure isn't exactly rocket science, but using a proper bearing race installation tool is critical. Trying to tap the race into position with a hammer can easily ruin its mating surface.