International S series (bus chassis)

Model overview

The Schoolmaster was produced as a variant of the International S1700 and S1800 (Class 6 trucks), with the lighter-duty S1700 and heavier-duty S1800. Along with powertrain configurations, the two model ranges were distinguished largely by suspension weight capacities.^[1][4] Following International traditional model nomenclature, the specific model numbers for the Schoolmasters ended in 3; gasoline-engine examples were given "23" model numbers while diesel-engine examples were given a "53" model number.

Powertrain

At its launch, the Schoolmaster was offered with four gasoline engines and three diesel engines (dependent on the model range specified). The S1723 was powered solely with gasoline engines, with the International 345 V8 as standard, with three optional gasoline V8s (the 392, and the MV404 and MV446). The S1823 was offered solely with the MV-series V8s (which ended production after 1981). The S1853 was powered by diesel engines, with a standard 9.0L V8, along with a DT466 and Caterpillar 3208 as options (the latter, discontinued around 1982, for the Schoolmaster).

For 1983, an S1753 was introduced to introduce diesel engines to the S1700 chassis; in place of the 9.0L V8 and DT466 inline-6, International debuted a 6.9L IDI-series V8. In 1987, the displacement of the IDI V8 was enlarged to 7.3L. A 4-speed manual was standard on the S1700 variants, while S1800 variants were equipped with a 5-speed manual; a 4-speed automatic was optional on all engines. Following the discontinuation of the MV-series engines, the S-1823 was phased out after 1981, while the S-1723 was phased out after 1986, after International withdrew production of gasoline engines entirely.

Model history

As with its predecessor, the 3800 would change very little over its 15 years of production. In 1991, the 3600 semi-forward control variant was introduced; this was a chassis designed for the Thomas Vista. After 1994, the lower-GVWR 3700 was discontinued. For 1995, along with all other International medium-duty trucks, the 3800 received chrome hood badges denoting the model series and its engine type; the grille badging changed from red to chrome.

A key event that would affect school bus manufacturing during the later 1990s was the completion of the acquisition of AmTran by Navistar in April 1995. By the end of the decade, AmTran buses would begin to start wearing International badging on the body as well. To promote the change, in 2002, International redesigned the hood for its conventional bus, dubbed the International IC. These wore vertical grille slats instead of horizontal ones seen since 1989 (although the horizontal grille slats continued to be produced for the 3800 until 2004). As it was a change intended to promote IC Corporation, chassis destined for Blue Bird or Canadian manufacturer Corbeil were still received with the standard hood and grille design.

Variants

3400

Navistar 3400 in use as a shuttle bus.

The 3400 was a chassis designed in the same fashion as a Type A cutaway school bus. To achieve a higher GVWR and allow for higher durability, instead of a van, the medium-duty International 4700 was used as a base. While primarily used by builders of transit buses and specialty vehicles, several body manufacturers (Mid Bus and U.S. Bus) would adopt the 3400 for school bus use.

In the school bus industry, Mid Bus and U.S. Bus both developed products based on the 3400, but the chassis became more popular in the transit and specialty vehicle industries instead.

All versions of the 3400 were powered by the 7.3L IDI and T444E V8 engines and used hydraulic brakes. As the 4700 was discontinued after 2001, the 3400 was replaced by the 3200 based upon the new-generation 4000-series trucks (later the DuraStar); currently, the 3200 is used only for transit bus, commercial bus, and specialty vehicle applications.

3600

Main article: Thomas Vista

Thomas Vista, the bus body paired with the International 3600 chassis

The 3600 was a chassis custom-designed for the Vista from Thomas Built Buses. The Vista combined design elements of a conventional and a forward control school bus. In comparison to a conventional, the driver sat further forward, closer to the front axle. Although much of the engine was located next to the driver like a transit-style bus, access from the front was also maintained via a traditional much-shortened hood. The 3600 chassis was designed in much the same fashion as International's step van chassis, borrowing many components from the 3800.

As it was originally designed specifically for the Vista's body, no other body manufacturers developed their own product lines based on the 3600. It was produced from 1991 until 1998 when Thomas chose to discontinue Vista production after the body manufacturer's purchase by Freightliner.

3700

1994 International 3700 with Thomas body

From 1989 to 1994, International offered two versions of its conventional school bus chassis (as it had with the S series). The 3700 was the lighter-GVWR model of the lineup; only minor differences in powertrain and weight ratings differentiated it from the 3800. The 3700 only was produced with the 7.3 engine.

After 1994, the 3700 was discontinued.

Powertrain

The 3800 is notable for being the first American school bus chassis to have an engine lineup consisting only of diesel engines. Unlike its S-series predecessor, the 3800 used an all-International lineup of diesel engines.

Inline-six diesel

• DTA360 (1989–1994)
• DT408 (1994–1995)
• DTA466 (1989–1998)
• DT466 Mechanical Injection
• DT466E Electronic Injection (1996–2005)

V8 diesel

• IHC 7.3L IDI (1989–1994)
• T444E (1994–2004)

Transmission

• Spicer 5-Speed Manual
• Eaton-Fuller 6-Speed Manual
• Spicer 6+1 Manual
• Allison AT545 automatic
• Allison MT643 automatic
• Allison A2000 automatic

Forward control (1981–2010)

Along with the traditional conventional-style cowled chassis, International produced several stripped-chassis variants for transit-style school buses. Using many chassis and powertrain components from the S series, the front-engine 1853FC (FC=Forward Control) was produced from 1981 to 1989. Unlike the conventional, it was powered exclusively by diesel engines. In 1990, the 1853FC was replaced by the more advanced 3900. As with its predecessor, it again shared powertrain and chassis components with its conventional counterpart. In fixing a key drawback of the 1853FC, the 3900 would significantly reduce the interior space needed for the engine, freeing up space for the driver's compartment and front stairwell. The 3900 was produced until 2010.

Rear-engine (1996–present)

In 1996, International introduced its first rear-engine stripped chassis since the early 1970s as the International 3000 became the chassis for the all-new AmTran RE. As with the 3900, the 3000 shared chassis and powertrain components with the 3800. Unlike its front-engine counterpart, the 3000 was designed for the use of both V8 and inline-6 diesel engines. Almost used exclusively used for AmTran and IC school buses, the 3000 remains in production as of 2014.