[1] In early 2001, Navistar entered into a 50/50 joint venture to produce commercial vehicles with Ford Motor Company,[2] officially named Blue Diamond Truck, LLC.

Under the agreement, Navistar assembled medium-duty trucks for both companies in its facility in General Escobedo, Mexico.

[3] Though externally different, both Ford and Navistar model lines would share a common chassis; the medium-duty Ford F-Series (which had already entered production in 2000 at General Escobedo[3]) shared its cab with the F-Series Super Duty line (F-250 through F-550).

Serving as the debut line of the NGV (Next-Generation Vehicle) cab structure, the new International 4000 series sourced its engines from within the company, carrying over the T444E V8 and DT466E I6 diesel (later VT365, DT466, and MaxxForce engines) from the previous 4000 series (sharing other commercial-grade drivetrain components with Ford and other medium-duty vehicles).

Semi-tractor International DuraStar In February 2001, Navistar released its all-new 4000 series, dubbed as "High Performance Trucks".

Sharing its chassis with the medium-duty Ford F-Series (introduced in 2000), the International 4300/4400 retained the DT466 and DT530 diesels of their predecessors.

The 4400 was also produced in a semitractor; sitting 4 inches higher than the chassis truck, the 4400 tractor was the only version offered with the DT570 engine as an option.

Sharing the cab of the DuraStar, the TerraStar sat on a lower frame and wore its own hood.

International Truck and Engine teamed with the Hybrid Truck Users Forum (HTUF), a consortium of utility industry customers, Eaton Corporation, the US Federal Government and the Calstart organization to assist with the cost of bringing the technology to market.