Project SuperBurb Iron Jock Currie Dana 60 Front Axle

The ingenious design that makes the Currie Iron Jock 60 so trick is the way the differential cover is mounted to the pinion gear at a 60-degree angle. This design ensures that the vulnerable stamped differential cover won't come into contact with rocks and other trail debris. The ductile iron housing weighs just 63-pounds empty and is manufactured using the latest vacuum pressure casting technology.

The Iron Jock 60's rotated cover orientation aids vehicle ground clearance by allowing the axle to slide over obstacles rather than catching on them. The theory here is that a round deflective surface is better than a square-edge one. The arrangement also places the differential fill plug closer to the center of the differential, protecting it and making it virtually impossible for the plug to come into contact with obstacles and accidentally come loose on the trail.

A look inside the Iron Jock 60 centersection reveals another intelligent design characteristic: the oiling system. Notice the two large openings above and below the larger perforation for the pinion gear. These are designed to provide restriction-free passage of gear oil during operation. The way this setup works is trick. Lube oil is pumped by the teeth of the ring gear as the differential rotates. The oil flows up to the front of the pinion housing through the upper passage and into a small reservoir between the two pinion support bearings. Inside the reservoir, the oil pools and is forced through each of the pinion support bearings by gravity. With this arrangement, half of each pinion support bearing is basically submerged in oil at all times. This, in turn, ensures that the bearings stay cool and last a long time.

Here is a look at the outside of the pinion housing-notice the bulged section of the casting; this is the upper lubrication channel as described earlier. The exterior of the housing features additional webbing in key areas for added strength. Notice the four holes on the top portion of the housing. These are designed to provide a footing for a fabricated steel bridge that makes mounting upper link mounts much simpler. Another thoughtful aspect Currie included in the design of the Iron Jock series is equal size pinion support bearings. Where most other differentials feature smaller bearings of different sizes, the Currie unit has two massive bearings of the same size.

Here, the Currie technician mocked up the axle to establish tube lengths and reference measurements. This step helped the technician determine potential problems with spring mounting location and bracketry spacing.

For this particular build, we picked up a set of Reid Racing kingpin-style knuckles for maximum strength. These knuckles are top of the line, featuring cast-iron outers and forged inner "Cs." These knuckles are constructed from high-grade material, with built-in ribbing in key areas for added strength. They are designed to enable high-steer arrangements as well as factory-style low steering setups. They come powdercoated bright orange for long lasting good looks. Due to their thicker proportions, these inner "Cs" required Currie's technicians to perform additional machine work to make the axletubes work with the knuckles.

The next step in the process was to cut the axletubes from a piece of 3/8-inch-wall, 3-inch-diameter DOM tubing. A large band saw was used to cut these tubes.

With each of the axletubes cut to the specific length, each was prepared for the next step on a CNC lathe. First, the pumpkin-side seal groove was cut into the tube, then the outer surface where the tube touches the centersection was cleaned.

This photo shows the difference between the completed inner portion of the driver-side axletube and the inner portion of the unfinished passenger-side tube. The stepped inner dimension will eventually house the inner axle seal, which prevents gear oil from entering the axletubes.

The exterior surface of each side of each axletube was cleaned to guarantee a perfect fit within the centersection and each inner "C."

The next step helped seal each axletube to the cast-iron centersection. Using 100-percent silicon rubber caulking material, the axletubes were coated thoroughly so that each could be set in place with little effort. The silicon provides a seal between the two parts for the finished product.

Here, the centersection is shown just after it was removed from a 450-degree oven. The heat expanded the material so that the room-temperature axletubes could slide into place with little effort. Once each tube was in place, the housing was allowed to cool for 45 minutes. As the centersection cooled, the tolerance between the tubes and the centersection began to shrink, making it virtually impossible for the tubes to move.

Next, the assembly is relocated to the table of a large industrial drill press. A different technician drilled twelve 1/4-inch holes at structurally specific locations where the axletubes intersect with the differential housing. These holes allow six Grade 8 Allen bolts to penetrate each axletube for added security.

The same drill press was used to thread all twelve holes. This process replaces the more common rosette welds you see on other axle housings. We like this process because it prevents the ductile iron centersection from becoming brittle from the heat of the welding.

Blue Loctite was used on each of the twelve 3/8-inch Allen bolts securing each axletube to the centersection.

Here, you can see how the bolts on one side of the centersection are closer together creating a triangle pattern within each axletube.

We were surprised to see each of the twelve bolts actually penetrate the inner surface of each axletube.

The Reid Racing inner "Cs" are based off of the massive Dana 70 model forgings and feature heat-treating to increase overall strength. You can see that Reid Racing leaves all the critical surfaces raw for fixturing and welding. These inner "Cs" are said to be the strongest version available through the aftermarket.

The Currie technician double-checked the orientation of each inner "C" in relation to the centersection.....

With the inner "Cs" tack-welded in place, the axle was mounted to a rotisserie machine so that the technician could weld the "Cs" to the axletubes without interruption.

Once each inner "C" was double-checked for proper position, the Currie technician welded each side of the "C" to the axletube. Next month,\ we'll show you how the remainder of the axle assembly parts were installed.