Mack’s hybrid tractor aims to replace U.S. Army’s M915 trucks

Mack Defense will display a hybrid-electric heavy tractor it built for the U.S. Army’s Common Tactical Truck program at the Association of the United States Army’s annual meeting in Washington, D.C., Oct. 12-14.

The truck is Mack’s on-road entry for the program and is designed to replace older highway haulers such as the M915 Line Haul Tractor. The Allentown, Pennsylvania, company said on Sept. 28 that the tractor will be on show at booth No. 7501 at the Walter E. Washington Convention Center.

According to Mack Defense, the Common Tactical Truck effort supports the planned modernization and eventual replacement of about 35,000 vehicles the U.S. Army uses for combat logistics, support and service-support missions.

The line haul tractor is based on Mack’s commercial Granite truck in a 6×4 configuration, meaning three axles with two of them driven. Mack says it is set up for moving heavy loads over long distances on highways and secondary roads. It shares its underlying design with Mack’s other prototypes to keep parts common across the family, which the company says simplifies maintenance and lowers lifetime costs.

All three of Mack’s Common Tactical Truck prototypes use high-voltage hybrid-electric systems. The company says they cut fuel use, allow extended “silent watch” operation with the engine off, and can export electrical power to equipment outside the truck. Mack pitches those features for situations where refueling may be limited and soldiers depend on onboard radios, electronics and possibly small field power grids.

Mack Defense began building the hybrid approach into its entry in late 2023, when it partnered with BAE Systems to integrate BAE’s Gen3 propulsion and accessory power management systems into its prototype.

The tractor also uses drive-by-wire controls, which replace mechanical links with electronic ones. Mack says that setup supports driver-assistance features including collision avoidance, blind-spot detection, driver alerts, anti-lock brakes, traction control and rollover mitigation, and leaves room for autonomous driving later. Other features include a new suspension for rough terrain, predictive maintenance technology meant to reduce unplanned breakdowns, cybersecurity measures, and an open systems architecture intended to make future upgrades easier.

“Our team used its experience in designing and integrating advanced vehicle technologies to build these next-generation trucks,” said David Hartzell, president of Mack Defense. “These upgrades will help provide the Army with safe, innovative, cost-effective, fuel-efficient and next generation tactical vehicles.”

Mack built three prototypes for the program: an on-road tractor, an off-road tractor and a load-handling system truck. The company also submitted designs for a cargo truck with a material handling crane, a wrecker/recovery truck and a tanker.

Arizona National Guard members drive an M915 tractor in California, June 10, 2021. Photo by Staff Sgt. Dillon Davis

The company received its prototype agreement on Jan. 27, 2023, when the U.S. Army awarded Other Transaction Authority deals worth $24.25 million combined to four teams: Mack Defense, Navistar Defense, Oshkosh Defense, and a partnership of American Rheinmetall Vehicles and GM Defense. Each team’s prototypes represented its offering for the M915 Line Haul Tractor and M1088 Medium Tractor, the Palletized Load System, and the Heavy Expanded Mobility Tactical Truck, and the service ran an operational demonstration of the designs in August and September 2024.

When the prototype contracts were awarded, Mack Defense said an initial production contract could cover more than 7,000 trucks valued at over $5.1 billion.

The route to that production contract shifted in January, when the U.S. Army said in a Jan. 21 notice, reported by Janes, that it was re-evaluating its truck replacement plan after reviewing industry responses to requests for information issued in the fall of 2025. Before that pause, the service had planned testing to support a single-vendor award.

On March 19, 2026, the U.S. Army published a commercial solutions opening for the program, moving its acquisition strategy toward readily available commercial products, Inside Defense reported. The solicitation covered six vehicle variants meant to replace the Palletized Load System, the Heavy Expanded Mobility Tactical Truck and the M915 Line Haul Tractor, and said the Army would not rule out firms that specialize in only one or two variants.

Mack’s announcement does not say whether the company responded to that solicitation, and it gives no production timeline, quantity or contract value.

The company’s booth will also feature three products from its parent, Volvo Group. They include a Prevost H3-45 motorcoach with 56 seats and a Volvo D13 engine, and a Volvo Construction Equipment L120 wheel loader adapted for military use with a fording kit for water up to 1.5 meters (4.9 feet) deep, a split cab to reduce height for transport, and lifting and tie-down points for air freight. A Volvo Penta D16, a 16.1-liter inline six-cylinder off-road diesel engine, completes the display.