Supporting a spectrum of construction and vocational operations, including repair and upkeep of airfields, roadways, landing strips, supply facilities, and motor pools, as well as snow removal and other civilian disaster-relief missions, the M917A3 Heavy Dump Truck is a commercial-based truck modified to meet mission-critical functionality that directly supports Army components.
According to Mack Defense President David Hartzell, whose company manufactures the M917A3 Heavy Dump Truck (HDT), the vehicle is
based on the commercially available Mack Granite dump truck.
“We took the base Mack Granite chassis and adapted it to meet some of the specific requirements that the U.S. Army was looking for in their third generation of heavy dump truck,” he explained. “Some of the notable things that the Army was looking for included basic militarization items, like NATO pintle hooks, 24-volt receptacles, jump-start capability, CARC [chemical agent resistant coating] paint, equipment racks, and personal weapon storage racks in the cab.”
He added, “And obviousl,y the Army also had mobility needs for military types of applications. So, we took the basic Mack [Granite] vehicle and worked with some of our ‘tier one’ suppliers, like Meritor, Hendrickson, and others, to develop a drive-line solution and a suspension solution that would give it the military off-road capability that the Army was looking for.”
More importantly, the Army wanted to increase the truck’s payload. Hartzell said the M917A2 and similar trucks being replaced are 6×6 platforms [one axle in front and two axles in the rear] and have payload capacities of approximately 18 to 20 tons, significantly less than the 27-ton payload requirement for the new “A3” systems.
ROBUST PROTECTION
“We designed our 8×8 truck [one axle in the front and three axles in the rear] to be able to hold 27 tons in a nonarmored version,” he said, adding that the expanded payload also allows for a certain number of vehicles to support an uparmored configuration that would provide protection against underbody blast and side-attack roadside bombs.
“The original goal was that they wanted about one-third of the vehicles to be armored and two-thirds of the vehicles be unarmored,” Hartzell said. “We developed an armor approach with a replaceable cab, because we can’t take our commercial cab body and armor it sufficiently to meet the levels of protection that the Army was looking for.”
Although the HDT armored cab is “three to four times heavier” than the commercial cab it replaces, the common interface design facilitates the ability for two soldiers to swap the vehicle from nonarmored to up-armored configurations in approximately 30 hours, he said.
“If a soldier goes from a non-armored vehicle to a full-up-armored vehicle, all of his human-machine interfaces are the same,” Hartzell said “The gauges are in the same location. The switches are in the same location. There’s no retraining necessary on any of that.
“Right now, our armored solution is one of the most robust, if not the most robust, force protection solutions on any tactical-wheeled vehicle in the U.S. Army fleet today,” he said. “We’re pretty proud about that, because at the end of the day, we all know that it will save soldiers’ lives.”
Significantly, he noted, the design not only meets today’s ballistic-protection requirements but also includes a margin that allows “future proofing” to potentially enhance the armor even more.
CAPTION: The M917A3 Heavy Dump Truck is based on the commercially available Mack Granite dump truck.
“In today’s world, we know that people are starting to look a lot at toplevel force protection,” he said. “Most designs before provide underbody blast protection based on the roadside bombs we saw in Iraq, Afghanistan and elsewhere. Now, it’s the drone situation that we’re seeing in Ukraine that they’re starting to talk about. And I suspect you’ll see some change in requirements going forward, that they will want some higher level of protection from the roof down because of the drone threat. …Fortunately, our vehicle is already designed to take quite a bit of additional extra weight and still maintain the payload ratings. So, if we have to create additional protection against ever-changing threats, we’re able to do that while maintaining the basic vehicle design that we have today.”
CONTRACTS AND TESTING
Mack Defense originally responded to the Army’s request for proposals on the M917A3 in 2017 and received the initial contract award in May 2018. The first test vehicles were delivered about 12 months later for Army testing at Aberdeen Proving Ground, Maryland, where they underwent a year of successful testing. Additional uparmored test assets were provided for additional testing in 2020, all of which led to the start of full-rate production in March 2021.
The original 2018 production contract was a five-year, base-contract award with two option years. Those option years have exercised, bringing the initial award quantity in the first contract to 683 trucks over seven years. The company celebrated production of 500 M917A3s in March 2025. That production number had grown to 549 by late August 2025.
Hartzell said that more recent discussions with the Army shifted “around spring of 2024” to begin exploring a possible contract extension, with the Army conducting its own market surveys and due diligence regarding potential competition before pursuing a sole-source contract with Mack Defense.
“I think a lot of it was driven around our armoring solution,” he said. “Because they know it’s very expensive to develop an armoring solution that is capable and that the Army would not have to retest.”
In August, Mack Defense announced its receipt of a new five-year contract to continue production of the M917A3 HDT for up to 450 additional trucks.
In addition to the commercialvehicle modification and armored cab capabilities, Hartzell emphasized the M917A3 reflects the Army’s goal it has with all of its new tactical wheeled vehicles to incorporate technologies found on commercial vehicles today that were not available when previous models were produced.
“If you look at the vehicles we’re replacing, like the M917A2s, they are approaching 40 years of age,” he said. “Some of the other vehicles out there are 50 years old. And they’re no longer sustainable. Additionally, none of those vehicles have any of the modern types of technologies, even simple things like antilock brakes. When’s the last time any of us have driven a vehicle that didn’t have antilock brakes?”
Hartzell said other advanced technologies taken from the commercially branded Granite truck can be found in the traction control system, vehicle switches and control instrumentation, and even sound levels in the cab.
At the other end of the technology spectrum, the high-tech advances are balanced against a range of low-tech benefits, such as ladder rung spacing and handle placements to minimize the risk of slips and falls.
As for potential future modifications or design improvements, Hartzell said the Army has not changed any requirements. That said, he acknowledged, “Our vehicles are evolving. So, there is opportunity to bring in even some other enhanced safety systems and things like that, that are coming in the next generation of Mack commercial product offerings. In 2027, our next-generation Mack Granite product will start coming out. So, we’re looking at all that and seeing what we could potentially offer back to the Army as a further enhancement.”
CAPTION: The Army recently awarded Mack Defense a new contract to build up to 450 additional M917A3 Heavy Dump Trucks.
Scott Gourley is a defense writer based in northern California. Commissioned through ROTC at the University of California, Los Angeles, he served in the U.S. Army as a field artillery officer for six years, then served about five years in the U.S. Army Reserve. He is a regular contributor to ARMY magazine and nearly a dozen other defense publications.
Full Article Available on Mack’s Site & On ARMY Magazine HERE
Mack Defense, a wholly owned subsidiary of Mack Trucks, is responsible for the sale of heavy-duty trucks to federal- and ministerial-level customers globally. For more information, please visit mackdefense.org.
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This effort was sponsored by the U.S. Government under Other Transaction Authority number W15QKN-17-9-1025 with the National Advanced Mobility Consortium, Inc. (NAMC). Reference herein to any specific commercial company, product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the Department of the Army (DA). The opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government, the DA, or the National Advanced Mobility Consortium, Inc., and shall not be used for advertising or product endorsement purposes. For more information, please visit www.namcconsortium.org.