In a factory Dana 60, material has been removed throughout the inside of the centersection as well as the area beneath the main cap supports, presumably to reduce weight. While few people have succeeded in breaking a stock Dana 60, shaving the centersection in such a manner doesn't do much for strength.
Instead of removing material from inside the centersection, Strange improves upon the original Dana 60 design by adding reinforcement ribs on the inside, and shaving material off of the outside of the case. Overall, the S60 case is thicker than the factory unit, and the main cap support area has been beefed up as well. The entire S60 case is cast from premium high-strength nodular iron.
Unlike a stock Dana 60 where the axle tubes are merely pressed and plug welded to the centersection, the S60 features welds around the entire perimeter of the axle tubes. This prevents the axle tubes from rotating inside the case, and eliminates oil leaks as well.
Strange offers both 35- and 40-spline axles with its S60 rearend packages. Consider that even the 35-spline axles offer more than double the strength our application requires, we opted for the smaller of the two options. The S/T axles are forged from an induction-hardened 1550 steel alloy Strange calls Hy-Tuf, which features a high nickel content to withstand big torque and bending loads. Rugged 1/2-inch wheels studs are also included.
Rounding out the S60's guts are a set of 3.73:1 gears, a 1350 steel pinion yoke, Timken bearings, and a Strange limited-slip differential. Standard limited-slips wear out their clutch packs over time, but the Strange design is a worm gear-based unit that eliminates wear, and provides an extremely progressive transfer of torque from side to side. Another advantage of the Dana/S60 is that it enables running a limited-slip with beefy 35-spline axles. Anything beyond 33-spline axles in a 12-bolt and 31-spline axles in a 9-inch requires stepping up to a locker or a spool.
With decades of experience under its belt, Strange has concluded that when a rearend whines, the pinion gear is usually the culprit. This is because it takes most of the beating during the assembly and manufacturing process. To combat potential noise issues, Kwas chamfered the pinion teeth to eliminate any sharp edges.
Polishing down the pinion gearshaft on a lathe is a standard OE manufacturing procedure, and Strange implements the practice as well. This enables the pinion bearing to be pressed on with minimal effort. Since the bearing may need to be pulled on and off several times during assembly to properly shim the pinion, polishing the pinion shaft reduces the chances of damaging it.
After pressing on the carrier bearings, it was time to install the ring gear. Instead of drawing the ring gear down to the differential by tightening up the bolts, Kwas prefers pressing it on. Using a large cylindrical slug of aluminum on the bottom of the press allows evenly distributing force on the ring gear face, reducing the potential of damaging the gear. Afterward, the ring gear bolts were torqued to 120 lb-ft.
Setting up backlash is typically a cumbersome and time-consuming process that involves shimming the carrier assembly to adjust the depth at which the pinion engages into ring gear. The S60's adjuster nuts thread into the centersection, and can be moved in and out with a spanner wrench to quickly and precisely dial-in backlash.