Mack Defense said Tuesday it has started production on five test platforms for the production vehicle testing phase of its $296 million deal with the Army to deliver its future heavy dump truck.

The company is building five M917A3 heavy dump trucks (HDT), which will then go into 40 weeks of durability testing beginning this summer.

Mack Defense’s M917A3, the Army’s future heavy dump truck

“Our production team and suppliers are excited to begin building these next generation HDTs for the U.S. Army,” David Hartzell, president of Mack Defense, said in a statement. “We’re confident the M917A3 will provide the Army the legendary durability and toughness Mack customers have come to depend on.”

The Army awarded Mack Defense the deal for M917A3 in May 2018, which is meant to begin replacing AM General’s M917 HDTs.

Deliveries for the new HDT, which is based off the Mack Defense’s civilian Mack Granite model, are expected to last through 2025.