The Dana 70 Axle: Everything Bullnose Truck Owners Need to Know

The Dana 70 is a heavyweight champion in the world of truck axles. Known for its incredible strength and durability, this axle is a popular choice for heavy-duty trucks that need to handle serious loads. Whether you’re driving a 1980-1986 Bullnose Ford truck or considering an upgrade, this guide will walk you through everything you need to know. From its history and technical specifications to its strengths, maintenance needs, and comparisons with other axles, we’ve got you covered.

Overview of the Axle

History

Introduced in the mid-1950s by Dana Spicer as a step up from the already robust Dana 60, the Dana 70 quickly became the axle of choice for trucks that needed to tow or carry significant weight. Over the years, it has been used in a variety of heavy-duty trucks, including Ford, Dodge, and GM models.

Applications

This axle was commonly found in heavy-duty trucks, particularly in 1-ton pickups and larger vehicles. In the Bullnose era, it was often used in F-350 models, where its strength was essential for towing and hauling. It’s also a popular choice for those upgrading their Bullnose F-250 or F-150 for serious off-road or towing duties.

Technical Specifications

Axle Type

The Dana 70 is a solid rear axle known for its heavy-duty construction. Available in both semi-float and full-float configurations, the full-float version is more common in heavy-duty applications. The full-float design means the axle shafts do not bear the vehicle’s weight, allowing it to handle much greater loads without failure.

Axle Shaft Splines

Typically featuring 35-spline axle shafts, although earlier models might have 23 or 30 splines, this axle offers significant strength. The 35-spline shafts make it well-suited for high-torque and heavy-load applications.

Ring Gear Size

With a ring gear measuring a hefty 10.5 inches in diameter, this large component is key to handling massive torque loads, making it ideal for vehicles that need to tow heavy trailers or carry substantial payloads.

Gear Ratios

The Dana 70 offers a broad range of gear ratios, typically from 3.54:1 to 7.17:1, making it versatile for various applications, from highway driving to off-road crawling. Higher ratios (numerically lower) like 3.54:1 are great for fuel efficiency on the highway, while lower ratios like 4.88:1 or 5.13:1 are ideal for towing and off-road use.

Weight Rating

The gross axle weight rating (GAWR) can range from 6,500 to 10,000 pounds, depending on the specific model and application. This incredibly high weight rating makes it one of the strongest options available for heavy-duty trucks.

Dimensions

The axle typically measures between 67 and 72 inches in width, flange to flange. The axle tubes are about 3.5 inches in diameter, contributing to its overall strength and durability.

Axle Weight

The Dana 70 is a heavy axle, with the full-float version weighing around 370 to 450 pounds, depending on the specific model. This weight is a testament to its beefy construction, designed to withstand the most demanding conditions.

Fluid Capacity

It typically requires about 4 to 5 quarts of gear oil, depending on the configuration. Proper lubrication is crucial to maintaining longevity, especially when used in heavy-duty or off-road environments.

Full-Floating Design

The full-floating design is a significant advantage in heavy-duty applications. In this configuration, the axle shafts only drive the wheels and do not support the vehicle’s weight, allowing for much greater load capacity and reduced risk of axle failure under heavy loads.

Pinion Support

The axle features robust pinion support with larger bearings compared to lighter models. This design reduces the risk of pinion deflection under high loads, which is essential for maintaining durability in demanding applications like towing or off-roading.

Strengths and Capabilities

Durability

Durability is where this axle really shines. It’s built to handle extreme loads, whether you’re towing a large trailer or off-roading with a fully loaded truck. The heavy-duty construction, including thick axle tubes and a large ring gear, ensures that it can handle the stress and strain of demanding applications.

Aftermarket Support

This axle benefits from solid aftermarket support, though not as extensive as the Dana 60 or Ford 9-inch. You’ll find a range of gear sets, lockers, and axle shafts available, allowing you to customize the setup for your specific needs. If you’re building a truck for extreme towing or off-roading, the aftermarket options will help you optimize its performance.

Versatility

The Dana 70 is versatile enough to be used in a wide range of applications, from heavy-duty towing to serious off-roading. Whether you’re driving on the highway with a heavy trailer or navigating tough trails, it can be built to handle it.

Common Upgrades

Popular upgrades include installing a locking differential for better traction, upgrading to higher spline count axle shafts, and swapping in different gear ratios depending on your driving needs. Strengthening the axle tubes and adding trusses are also common in extreme off-road builds.

Compatibility

The axle is compatible with a variety of brake setups, including both disc and drum brakes. It also works well with different suspension systems, making it a good choice for custom builds and retrofits. If you’re upgrading from a lighter axle, be prepared to make some adjustments to accommodate the dimensions and weight.

Maintenance and Care

Fluid Recommendations

Dana recommends using 75W-90 or 80W-90 gear oil, depending on the specific model and usage. If your axle has a limited-slip or locking differential, be sure to add the appropriate friction modifier to prevent chatter and ensure smooth operation.

Regular Maintenance

Regular maintenance is essential to keep the axle running smoothly. This includes changing the gear oil every 30,000 to 50,000 miles, checking the axle seals for leaks, and inspecting the bearings for wear. Given the heavy-duty nature, it’s also wise to inspect the axle tubes and pinion support for any signs of stress, especially if you use your truck for towing or off-roading.

Common Issues

While this axle is incredibly durable, it’s not immune to problems. Common issues include pinion seal leaks, especially under heavy use, and bearing wear in high-mileage axles. If you hear any unusual noises, such as whining or grinding, it’s important to inspect the axle to prevent more severe damage.

Tips for Longevity

To maximize the lifespan of your axle, follow the recommended maintenance schedule and avoid overloading your truck. Regular inspections of the seals, bearings, and gear oil level can help prevent major issues. If you’re off-roading, be cautious of the terrain and avoid high-impact situations that could stress the axle.

Comparison with Other Axles

Strength vs. Competitors

The Dana 70 is often compared to other heavy-duty axles like the Dana 60 or GM 14-bolt. While the Dana 60 is a popular choice for its balance of strength and weight, the Dana 70 offers even more durability and load capacity. Compared to the GM 14-bolt, it is similar in strength but has different aftermarket options and support. If you need the absolute maximum strength for towing or heavy-duty off-roading, this axle is hard to beat.

Ideal Applications

This axle is perfect for trucks that regularly carry heavy loads, tow large trailers, or tackle extreme off-road conditions. If you’re building a Bullnose truck for serious towing or off-road adventures, it’s an excellent choice.

Installation Notes

Compatibility and Modifications

Installing a Dana 70 in a Bullnose truck might require some modifications, especially if you’re upgrading from a lighter axle. You’ll need to ensure that the driveshaft, suspension, and brake systems are compatible with the size and weight of the new axle. It’s also important to consider the added weight and how it might affect your truck’s handling and fuel economy.

Brake and Suspension Considerations

Upgrading to a Dana 70 often involves upgrading your brakes and suspension as well. The increased strength and weight can place additional strain on your truck’s braking system, so disc brakes are often recommended. Suspension upgrades, such as stronger leaf springs or reinforced control arms, can help manage the extra weight and ensure your truck handles well on and off the road.

Frequently Asked Questions (FAQ)

Q: What makes this axle so strong?

A: The Dana 70 is built with thick axle tubes, a large ring gear, and robust bearings, all of which contribute to its strength. The full-floating design also allows it to handle heavy loads without stressing the axle shafts.

Q: How does the Dana 70 compare to the Dana 60?

A: The Dana 70 is stronger than the Dana 60, making it better suited for extreme towing and heavy-duty off-roading. However, the Dana 60 is lighter and has more aftermarket support, making it a more versatile choice for some builds.

Q: Can I swap a Dana 70 into my Bullnose F-150?

A: Yes, swapping a Dana 70 into a Bullnose F-150 is possible, but it may require significant modifications to the suspension, driveshaft, and brake systems. The swap is more common in F-250 and F-350 models where the truck is built to handle the axle’s additional weight and strength.

Q: What gear ratio should I choose for my Dana 70 axle?

A: The best gear ratio depends on how you plan to use your truck. Ratios like 4.10:1 or 4.88:1 are ideal for towing and off-roading, while higher ratios like 3.54:1 are better for highway driving and fuel efficiency.

Q: Is the Dana 70 compatible with disc brakes?

A: Yes, this axle is compatible with disc brakes, and many aftermarket kits are available for converting from drums to discs. Disc brakes offer better stopping power and are recommended for trucks that see heavy use or towing.

Q: How often should I change the gear oil in my Dana 70 axle?

A: It’s recommended to change the gear oil every 30,000 to 50,000 miles, depending on usage. If you’re using the axle for heavy towing or off-roading, consider changing the oil more frequently.

Q: What’s the best way to increase the strength of my Dana 70 axle?

A: To increase the strength of your Dana 70, consider upgrading to 35-spline axle shafts, installing a locking differential, and reinforcing the axle tubes with trusses. These upgrades will help the axle withstand extreme conditions.

Q: Are there any common issues with the Dana 70 axle I should watch out for?

A: Common issues with this axle include pinion seal leaks and bearing wear, especially in high-mileage or heavily-used axles. Regular maintenance and inspections can help catch these problems early.

Conclusion

The Dana 70 axle is a powerhouse, built for trucks that need to handle the toughest conditions. Whether you’re building a Bullnose truck for extreme towing, heavy hauling, or serious off-roading, this axle offers the strength and durability you need. With proper maintenance and a few strategic upgrades, it will keep your truck performing at its best for years to come.