Chevrolet/GMC B-Series

The Chevrolet and GMC B-series is a series of cowled chassis that were produced by General Motors, primarily fitted with school bus bodies throughout its production. Based on the medium-duty (Class 6-7) trucks produced by the Chevrolet and GMC divisions of General Motors, the B-series was produced in three separate generations; GMC initially produced its own version separate from Chevrolet. Introduced in 1966, the B-series was redesigned in 1984 and 1993.

Following the end of a supply agreement with Blue Bird Corporation, effectively leaving General Motors without a body manufacturer with which to supply chassis, the company exited production of full-size bus chassis, producing the later GMT560 solely as a cutaway-cab vehicle. The Blue Bird Vision entered production in 2004, becoming the first conventional-style school bus produced without a second-party chassis.

As of 2016, all General Motors-chassis buses are based on the GMT610 architecture (Chevrolet Express/GMC Savana).

Background

Prior to 1966, all medium and heavy-duty trucks of General Motors were derived heavily from the C/K-series trucks (and the Task Force trucks before them). Although using a stronger frame and suspension, much of the bodywork was shared. With the exception of divisionally-produced engines, the Chevrolet and GMC medium-duty trucks were largely identical to one another. Consequently, the conventional-type school bus chassis used for both divisions were largely the same.

First generation (1966-1983)

First generation (1966-1983)
Retired 1977-1983 Chevrolet school bus in use as a shuttle bus in North Carolina.
Overview
Manufacturer	Chevrolet GMC GMC Truck & Coach (1966-1970 GMC)
Production	Chevrolet: 1967-1983 GMC: 1966-1970 1971-1983
Body and chassis
Related	Chevrolet/GMC C/K medium duty GMC H6500 (GMC 1966-1970)

For 1966, the design commonality among the two divisions was split as Chevrolet retained the use of the C-chassis fo school bus use while GMC debuted a design based on its H-Series heavy truck. Following the consolidation of the two school bus chassis in 1971, the Chevrolet design would remain in production for a total of seventeen years.

Although General Motors redesigned the C/K product line in 1973, including the medium-duty trucks, the school bus chassis lagged behind, remaining in production until 1983.

Chevrolet (1967-1983)

In 1967, Chevrolet moved the medium-duty C/K to a dedicated chassis, taking the school bus chassis with it. As with the previous generation, the design was a rear-hinged "alligator"-design hood. The division offered its conventional school bus chassis with Chevrolet-produced engines, including the 250 inline-6 (replaced by the 292 inline-6), 366 V8, and 427 V8.^[1] In both Chevrolet and GMC school buses, the Allison AT475 3-speed automatic transmission became an option in 1971 with single or two-speed rear axles.^[1]

In 1974, the powertrain lineup was modified, as all GMC-built engines were dropped (alongside all diesel engines).^[1] In 1980, a diesel engine made its return as Detroit Diesel introduced an 8.2L V8.^[1] Dubbed the "Fuel Pincher", it was the first four-stroke engine produced by the company; the engine was available in naturally-aspirated and turbocharged forms.

GMC (1966-1970)

In 1966, the GMC division moved its school bus chassis from the medium-duty C/K to the all new H6500 heavy truck. A forerunner of both the GMC Brigadier and GMC General, the H-series trucks featured an all-steel front fascia with a center-hinged "butterfly" hood for engine access.^[1] Alongside GMC V6 and V8 gasoline engines, GMC school bus chassis were available with Detroit Diesel 6V53 V6 diesels.^[2]

In 1969, GMC transitioned its medium-duty trucks to the Chevrolet-based C/K medium-duty chassis introduced in 1967. The heavy-duty GMC school bus chassis remained in use by the division for 1970, before both divisions consolidated designs for 1971.

Second generation (1984-1991)

Second generation (1984-1991)
Retired late 1980s Chevrolet school bus in use as a church bus in Virginia.
Overview
Manufacturer	Chevrolet GMC
Production	1984-1991
Body and chassis
Related	Chevrolet/GMC C/K medium duty

By 1980, both Ford and International Harvester had released redesigned medium-duty trucks, leaving General Motors with a 7-year old product in the marketplace and its school bus chassis dating from 1967. In 1984, General Motors replaced its B-series school bus chassis by adapting it to the C/K medium-duty then in production, with commonality between Chevrolet and GMC.

Featuring a tilt-forward fiberglass hood as standard equipment, the B-series was powered by three V8 engines, the 366 and 427 gasoline engines and the Detroit Diesel "Fuel Pincher" diesel. From driver's compartment, the B-series shared a common steering column and nearly the same instrument panel as its predecessor. In 1990, the "Fuel Pincher" was discontinued by Detroit Diesel.

In 1985, a modified version of the B-series was developed for Ward Body Works. Considered a semi-forward control bus, the Ward Patriot shortened the front chassis with a layout in the style of a GM P-chassis, allowing for a shortened hood in the interest of improved driver visibility. The design would be developed further by GM with the Thomas Vista, another bus modified into a semi-forward control design from the B-series.

Third generation (1993-2003)

Third generation (1993-2003)
Late 1990s GMC school bus in use in New York.
Overview
Manufacturer	Chevrolet GMC
Also called	Blue Bird CV200 (with body)
Production	1993-2003
Body and chassis
Platform	GM GMT 530 platform
Related	Chevrolet Kodiak/GMC TopKick

For 1990, General Motors introduced its GMT530 medium-duty truck platform as the Chevrolet Kodiak/GMC TopKick, replacing the previous trucks of that nameplate, the GMC Brigadier, and the medium-duty C/K product lines. After a short hiatus (no 1992 examples were produced), the B-series based on the GMT530 entered production for 1993. As with its predecessor, the chassis was shared between Chevrolet and GMC, with only the grille differentiating the two.

The GMT530 B-series was powered by a range of gasoline and diesel engines. As gasoline engines were being phased out of school buses during the 1990s, the B-series became the last full-size school bus to offer them, with a 6.0L (366 cubic inch) V8 as standard. As the Kodiak/TopKick was renamed the C-Series in 1997, the 6.0L V8 was eventually phased out in favor of the Vortec 7.4L V8; the 7.4L V8 was replaced by a 8.1L Vortec V8 (one of the largest gasoline engines ever used in a school bus) in 2001. The Caterpillar 3116 was the first diesel engine option, joined by the turbocharged Caterpillar 3126 in 1997. Along with Allison automatic transmissions, the GMT530 B-series was available with either 5 or 6-speed manual transmissions.

The last manufacturer to offer a gasoline engine in a conventional-chassis school bus (prior to its reintroduction in 2016 in the Blue Bird Vision), a number of GM gasoline school buses were converted to use alternative fuels, including LPG (propane) and CNG (compressed natural gas). When GM replaced the GMT 530 series of medium duty conventionals with the GMT 560 series in 2003, no direct replacement for the B-Series was offered. However, the GMT560 would see use for bus builders with cutaway cab buses in many forms, alongside those based on the Freightliner M2 and Ford F-650 Super Duty.

Blue Bird CV200

Prior to 1992, the B-series chassis was available to any school bus manufacturer. That year, GM and Blue Bird signed a supply and marketing agreement, with the latter company becoming the exclusive supplier of the then-new GMT530 bus chassis for the next 10 years. The resulting model was named the CV200; while the GM B-7 (internal name for the GMT530-based bus chassis) was standard, Navistar International and Ford (later, Freightliner) chassis were available as options.

Along with the 1991 Navistar acquisition of AmTran, the agreement was a part of a series of mergers and acquisitions in the school bus industry between body manufacturers and chassis suppliers, eventually crippling the market share of General Motors as a chassis supplier as the agreement was not renewed. Effectively shut out of the industry as a full-size chassis supplier, General Motors ended chassis production in 2003 to concentrate on cutaway-chassis buses.

Usage by body manufacturers

While used nearly exclusively for school bus use, the B-Series chassis was adapted for a wide variety of uses by body manufacturers, ranging from bookmobiles to police buses. In the school bus industry, the General Motors chassis was popular for its wide range of engines. During the 1980s and 1990s, its continued use of gasoline engines remained popular, as the powerplants were sometimes used as the basis for conversion to alternative fuels, including LPG (propane) and CNG (compressed natural gas).

Following the chassis and supply agreement between General Motors and Blue Bird in 1992, the B-series was bodied exclusively by that company, nearly exclusively as a school bus.

• Blue Bird
• Carpenter Industries, Inc.
• Gillig Bros.
• New Bus Company
• Northern Coach
• Perley A. Thomas Car Works
• Superior Coach Company
• Thomas Built Buses, Inc.
• Ward Body Works
• Wayne Corporation

See also

Wikimedia Commons has media related to Chevrolet/GMC B-Series.

• Chevrolet Kodiak/GMC TopKick - B-Series donor platform (1993-2003)
• Ford B-Series, International Harvester S-Series "Schoolmaster", and International 3800 - competing school bus chassis
• List of buses

References