International Harvester S-Series

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International Harvester S-Series
1989 International S1754 dump truck.jpg
1989 International S-1700 single-axle dump truck
Manufacturer International Harvester (1978-1986)
Navistar International (1986-2001)
Also called Navistar International 4000-Series
Navistar International 8000-Series
Production 1977-2001
Body and chassis
Class Class 6-7 medium-duty truck
Body style
Truck (conventional)
  • Tractor
  • Straight truck
Layout 4x2
Related International S-Series "Schoolmaster"
International 3800
Engine Gasoline
197–236 hp (147–176 kW)
150–500 hp (110–370 kW)
Transmission Manual
Predecessor International Harvester Fleetstar (to 1978)
International Harvester Loadstar (1962-1979)
Successor International 4000-Series/DuraStar

The International Harvester S-Series is a medium and heavy-duty truck line that was manufactured by International Harvester. "S-Series" was first used as a label for the 1956 and 1957 Light Line trucks, until replaced by the A-series for 1958. The S-series label was reintroduced in mid-1977 as a replacement for the International Harvester Fleetstar. In 1979, other versions of the S-Series were introduced to succeed the Loadstar-series. Like the Loadstar, the S-Series were straight trucks commonly used for local delivery; the versions replacing the Fleetstar were semi-tractors or severe-service straight trucks. Additionally, the S-Series (and its replacement, the 3800) proved popular in the school bus industry. The S-Series was the last product line designed from the ground up by International Harvester themselves; it was produced in its original form until the end of the 1980s. Production of the second-generation S-Series ended in 2001.

S-Series (1955-1957)[edit]

1956 International Harvester S100

The origins of the S-Series nameplate date to 1955, when International Harvester introduced a successor to the R-Series for the 1956 model year. This S-Series was available primarily as light-duty (pickup) and medium-duty trucks, as the R-series of heavier trucks continued largely unchanged. Nonetheless, the heaviest versions (like the S-1840) had gross vehicle weights of 24,000 lb (10,890 kg) and 308 ci "Black Diamond" engines.[1] Production of the light duty S-Series ended in 1957, when it was replaced by the A-series.[2] As with its predecessor the R-series, the "S" also formed the basis of a full-size station wagon called the Travelall.

The S-184 heavy version was produced in Brazil by International's Brazilian subsidiary, until Chrysler bought it in 1966.[3]

First generation (1978-1989)[edit]

Navistar 2500 in use as a municipal service truck.

In April 1977, International Harvester unveiled the medium-duty S-Series at an event at the New Orleans Superdome.[4] Initial sales[when?] were of heavier-duty 2200, 2500, and 2600 models (28,000-45,000 lb GVW), replacing the Fleetstar. In the summer of 1978,[5] lighter-GVWR models (replacing the Loadstar) were released for sale.

Following the discontinuation of the IHC pickup-truck line in 1975, the S-Series was designed with a model-specific cab, replacing the pickup-truck cab used for the Loadstar (designed for the 1957 A-Series). More vertically-oriented than its predecessor, the design was much wider as well. To lower maintenance costs, all windows in the cab were designed with flat glass, including the windshield. Similar in style to the tilting hood introduced for the Loadstar in 1972, all S-Series trucks were given a tilting fiberglass hood.

The S-Series would be produced throughout the 1980s largely unmodified. 1987 would mark several changes to the S-Series trucks. To reflect the corporate change of the company from International Harvester to Navistar International, S-Series trucks saw changes in their badging (alongside all International vehicles). On the grille, the word "International" across the top of the grille was replaced by a red Navistar "diamond" logo alongside "International" in red at the bottom left of the grille. Inside, the IHC "tractor" logo on the steering wheel was replaced by a Navistar diamond logo. 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. Tandem-axle (6x4) versions of the S-Series were named F-series trucks.[6]

Models Replaced Notes





IHC Loadstar



IHC Fleetstar 2200 (short hood, wide cab)

2500 (long hood)

2600 (long hood, set back front axle)

Second generation (1989-2001)[edit]

During 1989 production, the International S-Series underwent a major redesign. In the interest of the aerodynamics, the truck was given a lower hoodline with smoother contours to the hood and fenders. In the interest of functionality, the interior controls were completely redesigned, with a new dashboard; a two-spoke steering wheel replaced the previous three-spoke design.

Although the exterior design was well-received, the interior saw several updates (replacing the instrument panel in 1992 and redesigning the rest of the interior in 1995). The second-generation models would remain in production until the end of the 2001 model year.


International 8100 4x2 tractor towing solar panels

For 1989, the S-Series naming scheme was updated, partially to reflect the redesign and in favor of the change from International Harvester to Navistar International. Bus chassis were changed from the traditional IHC xxx3 suffix to 3000-Series. Class 5-7 trucks (the previous S1600-1800) were rechristened the 4000-Series. Class 7-8 trucks (the previous S/F 1900 and above) were re-christened the 8000-series. The 8100 was a short-hood tractor, while the 8200 and 8300 were long-hood tractors designed similar to the aerodynamic 9400 Class 8 tractor.

Dropping their S-Series prefix, the popular 2500 and 2600 trucks continued in production as severe service vehicles, slotted below the Paystar in size.

Models Replaced Notes


Available in 4x2, 4x4, 6x4,6x6 drive
3600 Australasia-specific model, similar to 2500; model-specific hood







4500 & 4700 (low-profile chassis, LPX has short hood of 8100)

4900 is available in single/tandem drive







8100 (short hood)

8200, 8300 (long hood, set back front axle)

Bus use[edit]

Wayne Lifeguard school bus with International 3800 chassis (retired)
Navistar International bus in Mexico.

Throughout its production, the S-Series would be used as a cowled chassis for bus manufacturers. While 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. Introduced in 1979, the bus variant of the S-Series would be one of the final models designed by International Harvester before its transition to Navistar. In 1989, the S-Series bus chassis was rechristened the 3000-Series with the fitment of the new-generation Navistar cowl.

Produced until 2004, the bus chassis would outlive its truck counterpart by three years; its 25-year production run is the longest of any product ever sold by International Harvester or Navistar.


Models Replaced Notes


Loadstar 1703

Loadstar 1803

3600 See Thomas Vista

Produced 1992-1998






Name[7][a] Power[b] Type[c] Displacement Used
V345 197 hp (147 kW)@4000
309 lbf·ft (419 N·m)@2200
G V8 345 cu in (5.7 L) 1979-86
V392 236 hp (176 kW) G V8 392 cu in (6.4 L) 1979-86
MV404 210 hp (160 kW)@3600
336 lbf·ft (456 N·m)@2800
G V8 404 cu in (6.6 L) 1979-91
MV446 235 hp (175 kW) G V8 446 cu in (7.3 L) 1979-81
D150/170/190 190 hp (140 kW)@3000
340 lbf·ft (461 N·m)@2000
D V8 1978-79
IDI420 170 hp (130 kW)@3300 D V8 420 cu in (6.9 L) 1983-87
IDI444 D V8 440 cu in (7.2 L) 1986-89
DT466 210 hp (160 kW) D I6 466 cu in (7.6 L) 1979-89
210 hp (160 kW)@2800 D V8 636 cu in (10.4 L) 1979-81
3406 380 hp (280 kW) D I6 893 cu in (14.6 L)
350 hp (260 kW)@2100 D I6 855 cu in (14.0 L)
M11 500 hp (370 kW)@2100
1,550 lbf·ft (2,102 N·m)@1200
D I6
Detroit Diesel
230 hp (170 kW) D I6 426 cu in (7.0 L)[d]
6V92 335 hp (250 kW) D V6 552 cu in (9.0 L)
8V92 400 hp (300 kW) D V8 736 cu in (12.1 L)

See also[edit]


  1. ^ Engines are International unless noted.
  2. ^ The highest rated version of engine in the S-Series.
  3. ^ G denotes gasoline, D diesel, and I inline.
  4. ^ Detroit Diesels are supercharged 2-strokes.


  1. ^ Crismon, Frederick W. (2002), International Trucks (2 ed.), Minneapolis, MN: Victory WW2 Publishing, p. 272, ISBN 0-9700567-2-9 
  2. ^ "International Harvester History: Trucks". International Harvester. 1961. 
  3. ^ Shapiro, Helen (Winter 1991). "Determinants of Firm Entry into the Brazilian Automobile Manufacturing Industry, 1956-1968". The Business History Review 65 (4, The Automobile Industry): 879. doi:10.2307/3117267. 
  4. ^ Crismon, p. 485
  5. ^ Crismon, p. 492
  6. ^ Crismon, p. 495
  7. ^ "International Truck Specifications - S Line". Wisconsin Historical Society. 2013. Retrieved 2014-10-28. 
  • American Truck & Bus Spotter's Guide: 1920-1985, by Tad Burness.
  • International Trucks, by Frederick W. Crismon

External links[edit]