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Exploring The Beefy Dana 80 Axle

Posted in How To: Transmission Drivetrain on July 1, 2010 Comment (0)
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Exploring The Beefy Dana 80 Axle

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.

Jeremy and Pat Naeger at Custom Differentials have built scores of Dana 80 axles, and they can build 'em for mild to extreme rigs. This Dana 80 was modified to be used in the front of a vehicle or as a rear-steer axle. One of its most unique features is the adjustable knuckles. Jeremy and Pat Naeger at Custom Differentials have built scores of Dana 80 axles, and they can build 'em for mild to extreme rigs. This Dana 80 was modified to be used in the front of a vehicle or as a rear-steer axle. One of its most unique features is the adjustable knuckles.

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.

When compared to the popular Dana 60, the Dana 80 components are larger and heavier. For instance, here's a close-up of the Detroit Truetrac for the Dana 80. Eaton says it weighs 40 pounds, while the Truetrac for the Dana 60 weighs 25 percent less. When compared to the popular Dana 60, the Dana 80 components are larger and heavier. For instance, here's a close-up of the Detroit Truetrac for the Dana 80. Eaton says it weighs 40 pounds, while the Truetrac for the Dana 60 weighs 25 percent less.
To give you an idea of how stout Dana 80 components are, we placed a Dana 80 pinion shaft and ring gear (left) next to a pinion shaft and ring gear from a Dana 60. The Dana 80 pinion gear is 2 inches in diameter at its largest and 1.625 inches in diameter at its smallest and has 37 splines. The Dana 60 pinion gear is 1.625 inches in diameter at its largest and 1.250 inches in diameter at its smallest and has 29 splines (early Dana 60 pinion shafts had 10 coarse splines). To give you an idea of how stout Dana 80 components are, we placed a Dana 80 pinion shaft and ring gear (left) next to a pinion shaft and ring gear from a Dana 60. The Dana 80 pinion gear is 2 inches in diameter at its largest and 1.625 inches in diameter at its smallest and has 37 splines. The Dana 60 pinion gear is 1.625 inches in diameter at its largest and 1.250 inches in diameter at its smallest and has 29 splines (early Dana 60 pinion shafts had 10 coarse splines).
Dana 80 axles through 1998 used the larger pinion bearing on the left. After '98, the vast majority of Ford applications switched to the smaller pinion bearing shown on the right. Custom Diff notes that obviously the larger pinion bearing models are the most desirable because they spread the load over a larger surface area. Dana 80 axles through 1998 used the larger pinion bearing on the left. After '98, the vast majority of Ford applications switched to the smaller pinion bearing shown on the right. Custom Diff notes that obviously the larger pinion bearing models are the most desirable because they spread the load over a larger surface area.
In addition to a slew of rear Dana 80s, Custom Diff says that they've built several of these custom front Dana 80s over the years. This specific axle was made from a Dodge dual rear wheel application. It can be used either in the front of a vehicle or in the rear where rear steer is desired. They were able to machine the factory axletubes to accept Chevy Dana 60 outers. This specific axle is unique in that it has adjustable knuckles. Custom Diff installed adjustable flanges (pressed and then welded) that allow the knuckles to be rotated to compensate for changes in pinion angle. This means the alignment of the axle remains intact, no matter how much the axle is rotated. In addition to a slew of rear Dana 80s, Custom Diff says that they've built several of these custom front Dana 80s over the years. This specific axle was made from a Dodge dual rear wheel application. It can be used either in the front of a vehicle or in the rear where rear steer is desired. They were able to machine the factory axletubes to accept Chevy Dana 60 outers. This specific axle is unique in that it has adjustable knuckles. Custom Diff installed adjustable flanges (pressed and then welded) that allow the knuckles to be rotated to compensate for changes in pinion angle. This means the alignment of the axle remains intact, no matter how much the axle is rotated.
A tube was welded onto each knuckle, and they slide inside the Dana 80 axletubes. This adds strength to the assembly. To adjust the knuckle, you remove the flange bolts, rotate the knuckle to where you need it, and then reinstall the bolts. A tube was welded onto each knuckle, and they slide inside the Dana 80 axletubes. This adds strength to the assembly. To adjust the knuckle, you remove the flange bolts, rotate the knuckle to where you need it, and then reinstall the bolts.
Assembling the centersection of the Dana 80 is similar to other Dana axles. Custom Diff applies grease to the inner axle seals and the ends of the axleshafts to ensure that there's less chance of damage to the seals as the axleshafts are installed. Assembling the centersection of the Dana 80 is similar to other Dana axles. Custom Diff applies grease to the inner axle seals and the ends of the axleshafts to ensure that there's less chance of damage to the seals as the axleshafts are installed.
With the new Yukon bearings pressed onto the Truetrac and the new Yukon ring gear mounted using the twelve new 1/2-inch bolts, the unit was bolted into the housing and the pattern checked. With the new Yukon bearings pressed onto the Truetrac and the new Yukon ring gear mounted using the twelve new 1/2-inch bolts, the unit was bolted into the housing and the pattern checked.
This custom axle was fitted with Yukon 4340 chrome-moly Dana 60 35-spline inner and outer axleshafts. It's worth noting that the Dana 80 has 4-inch-diameter axletubes. By comparison, the axletubes on a Dana 60 are a hair over 3 inches in diameter. This custom axle was fitted with Yukon 4340 chrome-moly Dana 60 35-spline inner and outer axleshafts. It's worth noting that the Dana 80 has 4-inch-diameter axletubes. By comparison, the axletubes on a Dana 60 are a hair over 3 inches in diameter.
Spicer lockouts were modified to be used on this axle. The gears are made of machined steel and they're very strong. Custom Diff broached out the gears from 30-spline to 35-spline so that they would work with the Yukon outers. Spicer lockouts were modified to be used on this axle. The gears are made of machined steel and they're very strong. Custom Diff broached out the gears from 30-spline to 35-spline so that they would work with the Yukon outers.
The last step was to install the new cover and fill the axle with lube. Eaton does not recommend using synthetic lube because they say that some synthetics are slipperier than standard gear oil and alter the Truetrac's ability to bias torque. The last step was to install the new cover and fill the axle with lube. Eaton does not recommend using synthetic lube because they say that some synthetics are slipperier than standard gear oil and alter the Truetrac's ability to bias torque.
Brothers Jeremy and Pat Naeger are the pair who make Custom Diff run smooth. You'll usually find past 2008 Top Truck Challenge Champion Jeremy (left) manning the phones and running the front office, while wrenchmeister Pat works his magic in the shop. Brothers Jeremy and Pat Naeger are the pair who make Custom Diff run smooth. You'll usually find past 2008 Top Truck Challenge Champion Jeremy (left) manning the phones and running the front office, while wrenchmeister Pat works his magic in the shop.

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

129 1007 09+super tough dana 80 axle+eatons detroit truetrac limited slip

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.

Sources

Eaton Corporation
800-386-1911
www.eaton.com
Custom Differentials
Bloomsdale, MO 63627
573-483-3343
http://www.custom-differentials.com/

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