The super-tough Dana 80 rear axle ranks as one of the most desirable axles for off-highway use. It's a full-float unit with 11.25-inch ring gear diameter; 1.625-inch (minimum diameter) 37-spline pinion shaft; 11/2-inch-diameter, 35-spline axleshafts; and a 4-inch axletube diameter. It has an 11,000-pound gross axle weight rating and a continuous manufacturer's output torque rating of 2,500 lb-ft. As a bonus, there are quite a few Dana 80 axles available due to the fact they were used in a variety of mainstream applications over the years, including some '94-'02 Dodge 3/4- and 1-ton trucks and '88-and-later Ford F-350 and F-450 Super Duty dualie trucks.
Best of all, there are a slew of aftermarket upgrades available for the Dana 80. Gears, axleshafts, differential covers, lockers, and limited-slips are some of the ways to customize and beef the axle for specific vehicle weights, tire diameters, and uses.
To get a closer look at the Dana 80, we observed a rebuild of said axle at Custom Differentials in Bloomsdale, Missouri. This particular axle is very unique, as it has been modified by Custom Differentials to be used as a front axle or a rear-steer axle. For several years, it resided under the front of Custom Diff owner Jeremy Naeger's '72 Chevy Blazer, which was the high-flying cover truck in the August '02 issue. The axle has held up extremely well to the pummeling Naeger has bestowed on it over the years, and the rebuild was done mostly for preventive maintenance. The cool thing about using this specific axle for the story is that you not only get to see what makes the Dana 80 tick, you also get to see an example of how they can be modified.
We used a Yukon Gear & Axle bearing installation kit and a Yukon ring and pinion. We also installed an aluminum diff cover sourced from Randy's Ring & Pinion. One upgrade we specifically requested for this axle was the installation of Eaton's Detroit Truetrac. This incredibly tough helical-gear limited-slip differential is a favorite of ours. The helical gear design means that there are no wearable parts, meaning it's maintenance-free. No gear oil additives are required, and it offers smooth and quiet operation.
Since rebuilding a Dana 80 is similar to a rebuild on most all other Dana axles, this story will focus mainly on analysis of the Dana 80 components, as well as the unique aspects of this specific custom axle.
About Eaton's Detroit Truetrac Limited Slip
The Detroit Truetrac acts just like an open differential until needed. When a wheel begins to lose traction, the pinion gears (mounted in pockets in the case) separate slightly from the side gear and wedge in the pockets. As input torque increases, the separating force increases and slows or stops the spinning wheel. This allows torque to be distributed to the wheel with the best footing.
Because the Truetrac has no clutches or plates, no special lube additive is required. Finally, there is no break-in period required with
Want a Dana 80?
Most axle builders agree that the Dana 80 is a good choice for rigs making big power that are running up to a 44-inch-diameter tire. Custom Differentials has been building Dana 80 axles for years, and they have the expertise to build an axle specifically designed to match your rig. There are a number of configurations available, but expect to pay about $2,800 for a basic Dana 80 rear axle with a factory-type limited-slip differential. If you want a custom Dana 80 front axle with adjustable knuckles and a Truetrac as shown here, expect to pay about $7,640. A Dana 80 front axle without the adjustable knuckles will run about $6,240. Exact pricing will vary depending on your choice of locker or limited-slip, axleshafts, brakes, etc.