When four-wheelers upgrade to bigger tires, install Detroit Lockers, increase the engine horsepower, and add weight to their vehicles, they place enormous stress on the drivetrain components. One of the components that seems to reach its limit quickly is the front differential. The axles must be engaged and disengaged. The front wheels must be able to turn while power is being transferred out to the wheels. And the complete differential assembly must be lightweight but strong. Over the years, automakers and aftermarket companies have invested an incredible amount of effort into building a light but strong front differential. Unfortunately for hard-core or extreme four-wheelers, lower weight rather than strength is the priority for automakers. So where are we today?
Technical innovations are coming fast for off-road enthusiasts who upgrade their 4x4s to pursue more difficult trails and for those extreme 'wheelers who compete in rockcrawling championships. Everything from trick suspensions to stronger drivetrain components are being developed and tested on a daily basis. Regardless of which group you travel with, most of the big dogs agree that using a 1-ton Dana 60 in the front is the best insurance policy against breaking a frontend. However, there are a number of complications that a builder encounters when modifying a Dana 60 for a narrow-body vehicle that easily run the price to more than $7,000. The first problem is finding a good, used Dana 60 in a salvage yard, and that's not easy. For example, the Dana 60 we bought for our Ford truck came from Foothills 4x4 Center in Travelers Rest, North Carolina, and we live in California.
In many cases, the demand for front Dana 60s has pushed the price up to a point where it's cheaper to buy a new Dana 60 than it is to spend time searching for a used one that will probably be too expensive anyway. Another problem is converting the hub assembly from eight-bolt to five-bolt. Then there is the matter of rotors and brake calipers fitting inside a 15-inch wheel instead of the roomier 16-inch wheel on a 1-ton 4x4. And let's not forget that all the parts on a Dana 60 are heavy-duty, and that means they're more expensive.
There are also some negatives to consider when upgrading to a Dana 60 axle. A complete Dana 60 weighs more than a Dana 44, and it hangs lower to the ground. And nobody likes adding weight to his vehicle or reducing the ground clearance. Most four-wheelers work very hard to gain even a fraction of an inch in ground clearance.
Confused about upgrading to a Dana 60? So were we until John Currie of Currie Enterprises described the new Hybrid Dana 60 differential.
According to John, "If you've reached the point where you need the larger axle U-joints of a Dana 60, but already have a sizable investment in a Dana 44 or Ford 9-inch, then our new Hybrid Dana 60 is the answer for you. Using a customer's front housing and locker (third member), we adapt the late-model Dana 60 knuckles to the housing and machine axles to match the existing front locker to the 1-ton hub assembly. This way, you gain the stronger axle U-joint but without all the weight and reduced ground clearance inherent in a Dana 60. Best of all, you're using the investment in your existing housing, gears, and locker."
The centerpiece of the new Currie Hybrid front differential is the late-model unit bearing used on Ford trucks. The unit bearing is the all-in-one spindle, hub, and factory-sealed bearings used in '97-and-newer trucks. Currie machines the assembly to accept a smaller 12-3/16-inch rotor and fits it with studs for 5-on-5-1/2 wheels. Custom brackets hold new Wilwood brake calipers in tight in order to clear 15-inch wheels. The outer Dana 60 knuckles are machined to accept a custom steering arm for easy adaptation to almost any steering application. The inner Dana 60 axles are cut and splined to fit your existing Dana 44 or Ford 9-inch differential. When the 1-ton knuckles, axles, and hubs are completely assembled on your differential, the new Hybrid Dana 60 is about 50 pounds heavier and 2 to 3 inches wider overall (about 1 to 1-1/2 inches wider on each side). The extra weight is all muscle, and the additional width provides for a tighter steering radius. By using the parts you already have, the new Hybrid Dana 60 differential will cost you about half as much as a custom-built Dana 60.
After breaking numerous front axles and ring-and-pinion gears in a Dana 27 and a Dana 30, we installed a custom Dana 44 front differential nearly 20 years ago. Since then, the 4.88 gears and Detroit Locker have endured our abusive driving. The ball joints and tie-rod end require only normal maintenance and replacement. But we still break the factory stub axle and the axle U-joints on a regular basis (about two per year). Using the housing, ring-and-pinion, and Detroit Locker from our Dana 44, Currie Enterprises upgraded it to its new Hybrid Dana 60. Now, where will the weak spot in our Jeep be? Only time will tell. Here's the complete process.
More Axle Upgrades
If you're searching for an economic solution to give your front Dana 30 or Dana 44 differential more strength, then consider upgrading the front axles to the Warn High-Strength 4340 alloy axles with the larger Spicer 297X U-joints, and install its stronger, internally splined lockout hubs. This will nearly triple your axle strength over factory axles and significantly increase the lockout hub strength. The stock axles break at about 3,500 lb-ft, while it takes nearly 9,000 lb-ft to break a Warn 4340 alloy axle. This modification moves the weakest point from the outer axle to the axle U-joint, which breaks at about 4,500 lb-ft.
Until someone develops a stronger axle U-joint, there are only a couple of other things you can do to increase reliability on a front differential. The first is maintenance. Make sure that the axle U-joints are greased on a regular basis. This could mean disassembling the frontend if the axle U-joint is not equipped with a grease fitting. Secondly, machine the end of the axles to accept a full circle snap-ring instead of the standard C-clip. A full circle snap-ring will keep the cones at the ends of the U-joint from pushing through the eye of the axles and then catching on a ball joint, which will break the U-joint, the axle, or both. (Note: The Warn 4340 alloy axles come machined to accept full circle snap-rings.) Finally, keep off the throttle when the wheels are turned, especially if you're backing up. Tests show that the breaking point of an axle U-joint drops dramatically when the front wheels are turned.