Restored by Gary Mahan and his team in Basking Ridge, N.J., the massive Mack M100 once operated by Piscataway-based Hoffman Equipment represents a remarkable chapter in the history of heavy hauling and power plant construction.
The Mack M100 is not a truck that easily fades into the background. Standing approximately 15 ft. tall and 15 ft. wide, powered by a 1,000-hp. engine, and built to pull some of the heaviest loads of its era, it represents a time when America's expanding power infrastructure demanded extraordinary machines and the people who knew how to put them to work.
Today, this enormous piece of heavy-hauling history has a new home at the Mahan Collection in Basking Ridge. After decades away from its original operating environment, the M100 has undergone an extensive restoration led by museum founder Gary Mahan, who was determined to preserve the truck rather than see it dismantled for scrap.
For Mahan, the project was about more than bringing an old truck back to life. It was about saving a machine with a direct connection to New Jersey's industrial past, as well as to Hoffman Equipment, the Piscataway-based company that purchased the truck new and used it on major heavy-hauling assignments.
Machine Built for Extraordinary Loads
According to Mahan, the M100 was the largest Mack truck ever built. Its designation reflected its 100-ton capacity, and its size and power set it apart from conventional highway tractors.
The truck was purchased new by Hoffman Equipment.
Rather than hauling ordinary freight, the M100 was designed for specialized heavy transport, pulling a trailer with a reported 650-ton capacity.
Its assignments included moving enormous pieces of power plant equipment, including turbines and large electrical transformers. These were the components needed to build and expand the electrical infrastructure that served a growing nation during the 1960s, 1970s and 1980s.
Mahan recalled seeing the truck parked in Hoffman's yard approximately 50 to 60 years ago, waiting for its next job. It was an imposing sight even then, and the memory stayed with him.
The M100 was built for a different approach to heavy hauling than the equipment commonly used today. Modern heavy-haul trailers can employ dozens of axles and a large number of tires to distribute a load. The M100, by contrast, was designed to work with a massive, heavy-duty trailer, relying on its powerful engine and rugged construction to move loads that ordinary trucks could never handle.
These machines were essential to projects that required moving oversized industrial components from one location to another. Their work often went largely unnoticed by the public, even though the equipment they transported helped make modern infrastructure possible.
From Hoffman's Yard to a Preservation Project
Mahan's connection to the M100 stretches back decades, but bringing it into his collection required a fortunate combination of timing, persistence and a shared commitment to preservation.
After losing track of the truck for many years, Mahan eventually learned that it had returned to New Jersey. He spoke with its owner, but the prospect of taking on such an enormous machine gave him pause.
“What would I ever do with something so big?” he recalled thinking.
The opportunity resurfaced when a friend in New York contacted him with a warning: a scrap dealer was looking at equipment in the yard where the truck was located.
Mahan went to investigate and met the owner's son, who wanted to see the truck preserved rather than cut up for scrap. They reached an arrangement under which Mahan would acquire the M100 for the museum.
The truck was donated to the collection, giving the long-retired heavy hauler a chance at a second life.
For Mahan, that outcome reflected the larger mission behind the museum. His collection is dedicated to preserving historic trucks and machinery so that future generations can learn about the equipment that helped build America's roads, power plants and other essential infrastructure. The Mahan Collection Foundation is a nonprofit organization focused on acquiring, maintaining, restoring and displaying antique vehicles and equipment.
Two Years of Work
When the M100 arrived at the museum approximately two years before its restoration was completed, it was far from ready to operate.
The engine did not run. Some tires had deteriorated, the paint had faded and portions of the sheet metal had rusted through. Before committing to a full restoration, Mahan and his team needed to determine whether the truck could be brought back mechanically as well as cosmetically.
The engine was the first major concern. The team managed to free it up, then enlisted a Detroit Diesel specialist to get it running. Once the engine was operating, they were able to shift the transmission and confirm that the wheels turned.
That was a critical milestone. The truck had been delivered to the property on a heavy beam trailer and left sitting on blocks at the back of the yard. Establishing that its basic mechanical systems could function gave Mahan the confidence to move forward with the larger restoration.
The work that followed was extensive. The frame was sandblasted, the tires and rims refurbished and the radiator sent out for repair. The team tackled the damaged sheet metal, rebuilt and refinished components and completed the painting and final assembly.
Dozens of new hoses were installed, including air hoses, and the many small details that separate a running truck from a properly restored one were addressed along the way.
The heaviest work took place during the final year of the project, with the restoration reaching completion only a few months before Construction Equipment Guide (CEG) interviewed Mahan.
Mahan estimates that a typical restoration at the museum requires at least 2,000 labor hours. The M100 demanded even more.
“It's a process where you take it apart,” he said, describing the initial assessment, mechanical work and the search for parts. With older machinery, components are often no longer available off the shelf. Restorers must track down original pieces, find another truck to use as a donor or fabricate replacements.
Sometimes two or three trucks must be dismantled to obtain enough usable parts to rebuild one.
That challenge is familiar at the Mahan Collection, where restoration work is carried out on site across six barns housing a substantial collection of vintage trucks and construction equipment. Mahan estimates the property holds roughly 100 trucks and another 100 pieces of construction machinery.
Restored to Run, Not Just to Admire
One of Mahan's priorities was that the M100 should be more than a static display. He wanted it to be an operating piece of equipment, capable of giving visitors a sense of what it was like to experience such a machine firsthand.
To make that possible, the museum had a platform installed at the rear of the truck, complete with four seats and seat belts. The arrangement allows visitors to take a ride safely, bringing them closer to the experience of riding on a machine built for a very different era of heavy transport.
It is an appropriate finishing touch for a truck whose scale is difficult to appreciate from photographs alone. The M100's towering cab, enormous proportions and powerful mechanical presence offer a reminder of just how specialized heavy-hauling equipment once was.
The restoration also represents the kind of hands-on preservation that defines Mahan's operation. Rather than sending every project elsewhere, the museum carries out its restoration work on the property, relying on experience, ingenuity and a network of contacts to locate parts and solve problems.
Mahan's background makes him particularly well suited to the task. Before devoting himself to preserving historic machinery, he spent nearly four decades in the quarry and asphalt business. His family's operations supplied construction aggregate for projects ranging from major highways to residential driveways and the work gave him firsthand experience with the trucks and equipment that keep construction moving.
His father, Marvin Mahan, established the family business in the late 1960s. Gary subsequently took the reins, working with the family's various quarry and asphalt operations for decades.
That background helps explain why the collection extends beyond trucks to include construction equipment. For Mahan, saving these machines preserves a part of the working world he knew throughout his career.
New Chapter Alongside Hoffman Equipment
The M100's return to operating condition also has brought its former owner back into the story.
At the time of the interview, Hoffman Equipment had brought two of its service trucks to the museum: a vintage truck from the 1950s and a modern service vehicle. They were assembled alongside the restored M100 for a photo shoot, creating a visual connection between the company's history and its present-day operations.
The contrast was striking. The older service truck reflected the period when the M100 was working on heavy-hauling assignments, while the modern vehicle represented the continued need to support equipment in the field.
Its historic connection to the M100 makes the truck more than an impressive museum exhibit: it is a tangible link to the company's role in moving the oversized machinery needed for major industrial projects.
There was an additional personal connection at the museum that day, too. The man who had actually driven the M100 during its working years, Dennis Gartland (See Behind the Wheels…) was present for the occasion, offering an opportunity to connect the restored machine with someone who knew it in service.
For a truck that had spent years out of sight and faced the prospect of being scrapped, that was a fitting reunion.
The M100 is among the standout pieces at the Mahan Collection, but its restoration is part of a much broader undertaking.
Mahan began collecting vintage trucks more than four decades ago, when he and his wife used an old chain-drive Mack in place of a limousine for their wedding. One truck became two, then four and eventually a collection large enough to fill six barns.
Today, the nonprofit museum preserves vehicles dating from 1913 through 1993, along with a substantial assortment of construction equipment. The organization also shares its vehicles with other museums and dealers and takes selected trucks to shows and events, extending their reach beyond Basking Ridge.
The museum's work depends on patience and a steady stream of leads from fellow enthusiasts, former owners and families looking for a home for historic machinery. Some pieces are purchased, while others arrive as donations from people who want to ensure that equipment with personal or historical significance survives.
The Mack M100 embodies that mission particularly well. It is a machine that once performed demanding, specialized work in support of major infrastructure projects, then spent years in retirement before finding its way to a collection dedicated to keeping such equipment alive.
Its restoration required substantial effort, specialized knowledge and a willingness to tackle a project that many collectors might have considered simply too large.
But for Mahan, the reward is clear. The M100 is no longer a forgotten truck vulnerable to the scrap yard. It is once again a running machine, preserved for visitors who can see its scale, learn its history and appreciate the engineering behind it.
And although its days of hauling enormous power plant components are over, the truck still has a job to do: telling the story of the people, companies and machines that helped build America's industrial infrastructure.
For more information about the collection, visit The Mahan Collection Foundation The museum is located at 53 Cross Road in Basking Ridge, N.J., and publishes visitor information and tour dates on its website.
