This is it, the end of a six-part series converting a runof- the-mill Duramax dually into the ultimate working heavy hauler. Over the past six months this truck has gone through quite the transformation, with just about every aspect of the truck seeing an upgrade: performance, braking, steering, suspension, transmission, drivetrain, tires—even the bed was replaced for something more versatile for the farm/ranch duty this truck sees. Big horsepower was never a major concern, as basic tuning and some fuel system upgrades were enough to take this truck to a usable and safe 400hp level that offers more than enough torque to move a heavy tractor or trailer load of cows, all while keeping the rest of the drivetrain safe. The main objective was to turn this truck into a tool, something the owner could depend on and use daily to make his life and job easier. With the host of parts that were thrown at this project, we’re confident in saying the truck has become just that.


Since this truck is used daily to tow trailers of all shapes and sizes, improving upon the factory leaf spring suspension for better load control was a must. While the stock suspension handled the weight okay, once weighted down the rear end sagged quite a bit and the ride became rough since the overload springs were always compressed near max capacity. The Hellwig Products Big Wig Air kit solves these issues by placing an oversized airbag between the axle and frame on each side of the truck to help take some of that heavy load off the overload leaf springs, allowing for a more level ride when loaded. By taking weight off the leaf springs and handling it through the airbag, the truck will have a much more stable feel and smoother ride when towing. The airbags also allow a more level stance through different air pressure adjustments for the varying loads the big dually will be hauling. The Hellwig kit fit perfectly and installed in hardly anytime at all. Simply replacing the factory bump stop with the airbag and clamping the lower bracket around the frame and running the airlines and valve stems for pressure adjustments to the back bumper was all it took.

As the last part of the build on this truck, improving overall load control was the fi nal piece to the puzzle. To help handle massive loads and keep the stability and improve confi dence behind the wheel, the rear suspension will get some help from the Hellwig Products Big Wig sway bar and air bag kits.
The Hellwig Big Wig airbags are extremely simple to install on this model year GM as they will replace the factory bump stops bolted under the frame. The kit comes with the required brackets and hardware needed to install the kit in just 1-2 hours with hand tools.
The beauty behind the larger Big Wig bags is the size of the bags themselves; since they’ll hold a larger volume of air than most bags, the pressures needed to do the same job will be lower, which equates to a better ride and improved stability in a heavy load situation.
The versatile Channel Mount hitch system, also from Curt Mfg., is the ultimate in versatility for a truck owner who hauls different types of trailers on a regular basis. With the easily adjustable height and ball, and even a massive pintle hitch-style attachment, this system can be used to tow just about anything you’ll fi nd around the farm or jobsite.
Recapping the process of converting this everyday 3500 LB7 Duramax into the ultimate hauler, Part One introduced the project and upgraded some of the basics, including better fuel fi ltration with a Deviant Race Parts Cat Fuel filter kit and an improved turbo inlet horn. The engine and transmission both saw some improvements through the Duramaxtuner.com SPADE tuner, which improved shift strategies and increased power and torque with fi ve different performance programs to select from on the fly. The truck also gained manual shift control though the BD Diesel Tapshifter kit.
To keep those massive trailers under control when slowing, the Curt Manufacturing Triflex brake controller is installed for smoother stops, creating less stress on the cargo and trailer in tow. Being inertia-based, the Triflex uses an accelerometer to predict how much power needs to be sent to the trailer brakes to make consistent and confident trailer weight control from the driver’s seat.
Part Two took “work” to an all new level with the installation of a steel workbed from Bradford Built. The big flatbed made the truck much more versatile around the farm with the ability to haul just about anything, including ton-bales of hay, without hesitation. The top-quality bed came pre-wired with all the lighting and took Poulsen Trailers of Logan, Utah, just a couple of hours to install.
For the next round of upgrades, the Road Armor winch bumper was bolted on with two sets of Warn LED fog lights and their massive 16,500lb ti Winch. The addition of the Road Armor bumper did a few things for the truck; obviously, it provided an easy mounting place for the winch and lights, but it also added some increased strength and front end durability as well. Plus, it looks great hanging up front.
To help with load control, the BD Diesel exhaust brake system was installed under the truck inline of the previously installed 4” exhaust system. The air-actuated butterfly mounted in the exhaust basically restricts exhaust from exiting the engine to create back pressure within the engine and help maintain or slow engine rpm to aid in braking when towing heavy on long, steep grades. The brake works so effectively that in normal day-to-day driving the factory service brakes rarely need to be used.
In basic stock form, the big dually looked like just about every other farm truck you come across. It had probably never seen a car wash before, steel cords were showing through mismatched tires, and its busted and cracked dually fenders had seen a little too much off-road abuse. But these issues with the truck were mainly cosmetic; the rest of the truck was sound and in good shape with just 68,000 miles on it when this build started.
How the truck sits today with a host of goodies bolted on. The new Hellwig airbags and Bilstein shocks help keep the truck riding nice and sitting level when towing a dozen one-ton hay bales from the field to the feed lot. The Duramaxtuner.com tuning increased horsepower and torque to keep that load moving forward, while the BD Tapshifter and Exhaust Brake help bringing it to a stop. And how could you look past those brand new Ultra Predator dually wheels with General Grabber AT2 tires to for better mud and snow traction?

To help with sway control when towing top-heavy loads down winding canyon roads, the rear suspension also received one of Hellwig’s Big Wig sway bar kits. The massive sway bar can help reduce sway by over 20% in most applications, keeping the truck flatter through the corners and equating to a more stable trailer and much more confidence in the driver’s seat. The sway bar can also improve traction while cornering since it’ll help improve the tires’ contact patch on the ground, which helps greatly for this truck that spends a lot of time on dirt and gravel roads outside of town. The lifetime warranty and easy installation made it no brainer for this build and helped take the trucks overall towing performance to an all new level.


This truck had already been running a basic trailer brake controller, but after more than ten years of service the system needed some updates. Curt Manufacturing’s new Triflex brake controller uses a state-of-the-art, triple-axis, motion-sensing accelerometer for super responsive smooth stops, regardless of trailer weight or axles. The automatic leveling and calibration system eliminates the need to set anything up and offers nine different sensitivity levels, along with user-selectable power output and trailer brake light activation. The Curt Channel Mount trailer hitch system also offered the truck owner some major versatility for towing just about anything on the property. The dual ball adapter has a 2” and 2-5/16” ball on it and the channel mount allows more than 11 inches of height adjustability just by pulling the pins and moving to the height you need.

The Bradford Built workbed has become an invaluable addition to the truck. It really does make working around the farm easier with more room for hauling stuff without worry of busting up stock fiberglass bedsides or dinging up a bed floor when tossing heavy tools and tractor parts around. The Titan Hammerhead transfer tank and toolbox combo is also proving its worth by allowing in-field fuel-ups and plenty of storage space for the tools and equipment a farmer needs to get his daily tasks completed.

Over the course of a summer, the help of a handful of suppliers, and who knows how many hours in the shop and garage installing everything, this basically stock 2003 LB7 Duramax dually was taken from what was a perfectly capable daily driver and tow rig to the ultimate towing platform. The increased mileage, power, and torque have been welcome when 14,000 pounds are hooked on to the gooseneck hitch. The addition of an exhaust brake, transmission tapshifter, airbags, sway bar and brake controller offer a better sense of confidence for the operator, as the truck just feels better keeping the heaviest loads under control. Improving on the fuel system with a performance lift pump and better filtration should improve engine longevity and efficiency, while the steering upgrades beefed a somewhat failure-prone design to take any abuse it’ll see off-road. And the addition of a big steel flatbed, heavy duty bumper, a winch, and 100-gallon transfer tank/toolbox combo added so much more versatility and ability to get work down around the ranch. This truck has become the owner’s new favorite tool. DW
















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