Chevrolet and GMC

1972-1978

In 1971 and earlier, Chevrolet and GMC each used its own independent VIN system. The 1972 model year coincided with a wave of standardization being imposed for General Motors divisions, and VIN length and formats were made consistent across the board.

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Position 1: Manufacturer

Positions 2, 4-5: Model

GM's official documentation claims that the "2" code in the fifth position indicates a chassis-cowl in some years, and a forward-control truck in others. Likewise, "3" was used to designate both a chassis-cab and a chassis-cowl. In practice, it appears that both codes were used on school bus chassis interchangeably!

Position 3: Engine

Other letters were no-doubt used, but it seems that nigh every surviving bus of this era has the same gas lump under the hood.

Position 6: Model year

Position 7: Assembly plant

Positions 8-13: Production sequence

Chevrolet serials began at 100001, while GMC serials began at 500001. Each series reset at the start of each model year.

1979-1980

In 1978, GM made changes to the format of VINs on medium- and heavy-duty trucks in order to implement a more explicit indicator of gross vehicle weight. This may have been done in anticipation of the 1981 industry-wide standardization of formats. Light-duty trucks continued using the prior VIN system through 1980.

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Position 1: Manufacturer

Positions 2-4: Model and gross vehicle weight rating

Position 5: Engine

Position 6: Model year

Position 7: Assembly plant

Positions 8-13: Production sequence

Chevrolet serials began at 100001, while GMC serials began at 500001. Each series reset at the start of each model year.

1981-1991

In 1981, GM adopted the uniform 17-digit VIN format being imposed throughout the industry.

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Positions 1-3: Manufacturer

It appears that all school bus chassis production was consolidated at the GMC plant in Pontiac, Michigan by 1981. Had chassis been built in Oshawa or London, Ontario during this period, the "2GB" and "2GD" manufacturer prefixes would have been used:

Position 4: Gross vehicle weight rating and brake system

Positions 5-7: Model

Position 8: Engine

Position 9: Checksum

0-9 or X, calculated from the other digits.

Position 10: Model year

GM's model years typically began in August of the preceding calendar year. The S60/S6000 bus chassis ended production at the end of the 1990 calendar year, making 1991 models somewhat rare.

In spite of the development of derivative forward-control models during the 1980s, GM hardly invested in its school bus chassis in this timeframe. The S60/S6000 was not updated from "1967" styling to "1973" styling until partway through the 1984 model year.

Position 11: Assembly plant

Positions 12-17: Production sequence

Chevrolet serials began at 100001, while GMC serials began at 500001. Each series reset at the start of each model year.

1993-2002

After discontinuing its S60/6000-series bus chassis a little over a year before, GM made a halfhearted re-entry into the market with the unveiling of a redesigned chassis-cowl for the 1993 model year. Designated B7, the new chassis was exclusive to Blue Bird and built at GM's Janesville, Wisconsin truck plant. Apart from the introduction of new code designations, the VIN format did not change.

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Positions 1-3: Manufacturer

Position 4: Gross vehicle weight rating and brake system

Positions 5-7: Model

Position 8: Engine

Position 9: Checksum

0-9 or X, calculated from the other digits.

Position 10: Model year

Production of the 1993 B7 began by July 1992, and model year changeovers happened in July or August through its entire duration. By the early 2000s, GM's model years were the least "inflated" of any manufacturer in the school bus industry.

Position 11: Assembly plant

Positions 12-17: Production sequence

Very early 1993 chassis were numbered off from 610001 for Chevrolet and 650001 for GMC. Before the end of the 1992 calendar year, the sequencing changed to the traditional startpoints of 100001 for Chevrolet and 500001 for GMC, resetting at the start of each subsequent model year.

This continued through 1999. Starting with 2000 models, Chevrolet chassis began to be interspersed in the GMC serial sequence.

Epilogue

GM exited the large school bus market in 2002, with the exception of a small number of buses built in the mid-2000s from C5500-series cutaway cabs.

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©2021 Andrew Turnbull.