The chassis was produced with both gasoline and diesel powertrains (the latter exclusively after 1986), single or tandem rear axles, and two, four, or, six-wheel drive layouts.

After 2001, International phased in product lines based upon the "NGV" architecture; severe-service and bus chassis variants produced through 2003 and 2004, respectively.

During 1955 production, the R series model family underwent an update, with International renaming its light-duty and medium-duty trucks the S-series.

[1] The initial lineup consisted of heavier-duty 2200, 2500, and 2600 models (28,000-45,000 lb gross vehicle weight rating - GVWR), replacing the Fleetstar.

In a major shift, for 1987, International became the first truck manufacturer to produce a medium-duty product line powered exclusively by diesel engines.

Originally intended to use the International Tristar nameplate, the S series consolidated the aging Loadstar and Fleetstar trucks under a single product line.

To accommodate larger-bore diesel engines under a standard-length hood, the S2200 was fitted with a widened cab (distinguished by a two-piece windshield).

To optimize aerodynamics, the model line was given a lower hoodline and closer-fitting fenders (with halogen headlamps and wraparound turn signals).

From 1989 to its 2001 discontinuation, the exterior remained nearly unchanged; in 1992, Navistar changed the design of the instrument panel, updating the entire interior in 1995.

Used primarily for yellow school buses in the United States and Canada, the S series also was used outside of North America as a basis to produce other types of bus bodies.

The unrelated Australian ACCO cabover truck built under various guises by IH and IVECO was produced with the same cab architecture for 47 years.