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World’s Largest Mack Truck Is Getting a New Shot at Life After 55 Years

It’s said to be the last survivor of three ever built, and a collector in New Jersey is restoring it for others to enjoy.

byCaleb Jacobs|
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For every perfectly preserved, eight-figure collector car that surfaces at Amelia Island or Monterey, there's a vehicular treasure that's stashed away for good, never to be seen or enjoyed by the public again. While it's clearly different from a pre-war Bugatti, my mind goes to Ford's experimental turbine semi-truck named "Big Red," which was hidden for years until my old coworker Peter located it. Something in that same vein is happening in New Jersey right now as the last surviving Mack M100SX, the largest truck ever built by the manufacturer, is being restored after decades of disuse.

Normal tractors have nothing on the M100SX. It's so gargantuan and so specialized that Mack built just three of them in the mid- to late-1960s; this one was completed in April or May 1967. It measures 32 feet, 1 inch from the front bumper to the back of the frame. From the ground to the top of the cab, it's 13 feet, 6 inches. And the weight? Even without the body, it clocks 95,485 pounds according to the original literature. The GVWR is massive at 331,875 pounds, meaning its payload capacity exceeds 100 tons.

The original engine is a two-stroke Detroit Diesel 12V149T, which translates to twelve cylinders arranged in a V at 149 cubic inches each. My rural public school education helps me calculate the total displacement at 1,788 cubic inches, or 29.3 liters (OK, I had to Google the conversion on that). It's twin-turbocharged to 1,000 horsepower and makes 2,500 lb-ft of torque at 1,900 rpm. I can only imagine the size of those pistons since every cylinder has more displacement than an entire Honda Civic engine—and there are 12 of 'em.

Via The Mahan Collection Foundation
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I first heard rumblings of the behemoth's resurrection on Facebook, where retired truckers reminisced about spying on the truck in a past life. Several noted it had been moved from its longtime resting place, the Pile Foundation Construction lot in Far Rockaway, New York, on Long Island. Some searching around the web turned up a video of the Mack being transported in pieces by Dave's Heavy Towing out of Hillsborough, New Jersey, and the sight was spectacular.

As it turns out, the Mack was on its way to The Mahan Collection in Basking Ridge, New Jersey. It's run by a foundation whose goal is to preserve and restore antique commercial vehicles, bringing a freshly finished project to the biggest truck shows each year. Gary Mahan is the leading man there, and he was contacted to rescue the M100SX given his connections in the heavy-duty vehicle space.

"Within the last five years we have heard that it was available for sale," explains Kathryn Piper, vice president of The Mahan Collection Foundation. "We have tried to make an offer at one [other] point but could not come to an agreement."

That changed when the Mahan group learned the previous owners were considering cutting it up for scrap. Knowing that, Gary called on his network of truck and history enthusiasts to set the plan in motion. Now it's home in Basking Ridge, and the Mahan Collection Foundation intends to restore it to running condition, sandblast it, and paint it for display so the public can appreciate the feat of mid-20th century engineering.

Via The Mahan Collection Foundation

Piper was able to provide lots of background information on the M100SX, including the truck's original build sheet, sale specs, and schematics. It was originally built as an off-highway dump truck, though it later was converted to a towing tractor with its own specialized trailer. The Mahan Collection acquired only the truck, serialized "M100SX1003" as the third and final in series production.

Records show the machine was first delivered to Hoffman Rigging and Crane in New Jersey on Jan. 21, 1970. Piper tells me The Mahan Collection Foundation remembers the Mack parked in Hoffman's yard along Route 287 during the 1970s and '80s, though at some point, it was moved to Texas. It spent a while in service for Mashburn Trucking but was later acquired and driven back to New Jersey. That trek took two full weeks on the road as the rig tops out at 28.8 miles per hour. Talk about a trip.

Legend has it that Mack M100SX1003 helped expand the Newark Airport time and time again during its later years. With its specialized, eight-axle trailer, the truck was loaded with 1,000 tons of rock and rubble to "proof" the material. When the Mahan Collection began extracting the truck, it was still mated to the trailer, though it was only possible to take the Mack. Given the size and weight of the trailer, it could only be shipped on a barge or cut into pieces. They chose to leave it as it wasn't original.

The Pile Foundation Construction company presumably found a more fitting workhorse for the job and parked the Bulldog beast in its yard where it sat until roughly two weeks ago.

It's more than exciting to see a piece of American work history be preserved for the next generations to see. I've included all the paperwork provided by the Mack Trucks Historical Museum so you can view it in its entirety. Notice all the comprehensive measurements, many of which were taken with the truck's original dump body installed. Mack measured the machine's turning radius at a full 90 feet, for instance, and there are plenty of cool specs related to the crazy-stout frame. Or if you want to read about the Detroit Diesel's Ingersoll-Rand air starter, that's all in there too.

Thank you for geeking out with me on this. I can't tell you how much joy it brings me that people care enough to save a machine like this, and also that I get to help tell its story. This is what it's all about.

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