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

After finalizing the pinion depth, it was time to dial in the backlash, which simply determines how much the pinion gear will turn before engaging the ring gear. Moving the spool and ring gear closer to the driver side using carrier shims increases backlash, while moving it closer to the passenger side decreases backlash. Bill says that a range of 0.008 to 0.012 inch is acceptable, but he prefers a tighter 0.008-inch setting when using new gears so that backlash will still be within the ideal window once the ring-and-pinion assembly fully breaks in.

The crush sleeve, situated between the front and rear pinion bearings, prevents inadvertently over tightening the yoke on the bearings, however, it can take up to 400 lb-ft of torque to crush it, so an industrial-grade impact wrench is a must. Bill recommends cinching down on the pinion nut until all free play in the yoke is gone, then tightening it another 20 inch-pounds. Note how the front axle braces attach to the left and right sides of the differential housing.

Pinion depth is the distance between the centerline of the axles and the flat face of the pinion gear, and is altered by installing adjustment shims between the pinion gear and pinion bearing. With a 0.030-inch shim, the pinion wasn't engaging the ring gear deep enough. Swapping in a thicker 0.032-inch shim yielded an ideal gear contact pattern.

Bill's a fan of simply painting a rearend, since a thick powdercoat can hide stress fractures. As the saying goes, the finished product is almost too pretty to put underneath a car.

With the differential assembly installed and the gear setup finalized, Bill slid the axles into the housing. This angle clearly illustrates how the C-clip eliminators firmly hold the axles to the backing plate flange in the event of failure. Welding on housing ends off of a 9-inch rearend works just as well as the C-clip eliminators, but requires upgrading to disc brakes. For this reason alone, we opted for C-clip eliminators, which enable retaining the stock rear drums to keeps costs to a minimum.

The aluminum differential cover provided by Strange certainly adds some visual pop, but its primary benefits are reducing distortion of the differential housing and stabilizing the main bearing caps. This, in turn, helps maintain proper pinion depth and gear backlash. The cover's two load bolts are positioned to come in contact with the center of each bearing cap as they're cinched down, which provides cap preload and reduces the likelihood of distortion. After tightening the 10 cover bolts to 25 lb-ft, Bill torqued the load bolts to 10 lb-ft using an Allen wrench. Next, the jamb nuts were tightened to 10 lb-ft to lock everything in place.