Vehicle Identification Numbers (VIN codes)/GM/VIN Code History
GM VIN systems 1935 through the 1980s.
editGM divisions used various systems to number their products, generally the most basic was ascribing a year (usually the model year which began in the latter part of the calendar year beforehand), generally abbreviated to the last two digits (e.g. 34 for 1934) and then a unit number which was a production sequence number (PSN). Some divisions added a code to identify the model level, as in Buick’s Special, Super, Roadmaster, and Limited.
For the1935 model year GM Canada decided to expand that to formalise their serial numbers into the format we start to recognise as a VIN. Using the last digit of the model year, followed by a four digit model code, the last two digits being the Fisher body type number (e.g. 11 for a two door sedan/coach). The first digit identified the brand (e.g. 1 for Chevrolet, 7 for Pontiac) and the second a model trim level. Then the PSN was formalised into 6 digits (it became common for PSNs to start at 100001 rather than 000001 but I’m unsure when this practice began).
There was a chance that a unit could be assigned an identical number to that of one from a decade before. I am too far removed in time and space to research whether a system was implemented to ensure that didn’t happen, or it was considered so remote a possibility or that the chances of them also being registered in the exact same jurisdiction was unlikely (or maybe that most 10 year old cars would have been decommissioned by then). Somewhat conveniently with no wartime models built this couldn’t happen for early 1950s models anyway.
A change to the Canadian system was the addition of a single digit (6 or 8) for MY1955 thru MY1957 to allow for the now two types of engines (L6 or V8) available in both Chevrolet and Pontiac lines (previously only 6 cylinders were available in both in Canada for many years) but removed it for MY1958 as the model numbers now reflected the engine configuration.
In the US for the 1960 model year Chevrolet adopted much the same system, modified to preface the PSN with a letter denoting the assembly plant (Chev sold over a million units annually which meant the 6 digit numbers were insufficient to guarantee uniqueness for the whole year without this extra piece of information).
I suspect since Chevrolet was way and afar the leading producer its need to computerise its systems was greatest, and thus the rewards greatest it was chosen to be the lead division. It’s possible this was when the term Vehicle Identification Number (VIN) was invented, maybe by one of these new fangled (computer) systems analysts.
From the 1965 model year the system was applied to the other US divisions (Cadillac last, in MY1971). At this time the model code was expanded to five digits and for US production it was modified to move the model code to the first five positions with the model year digit at position one; this ensured there could not be a 1970 Chevrolet with the exactly identical number to a 1960. The same expansion of the model code occurred for MY1965 in Canada but the year remained in position one for two more years after which (MY1967) it adopted the same format as the US cars.
Possibly as GM rolled out computerisation in their international divisions, Vauxhall (UK), Holden (Australia), GMSA (South Africa) and GM do Brasil all switched to using a standard VIN for the 1968/9 model years for all except Vauxhall as new mainstream models debuted (HK Holden, Opel Rekord and Chevrolet Opala respectively). For some unknown reason Opel (Germany) retained its own serial number system that was similar to those which the US GM divisions had used earlier. GMSA uniquely added an A after the model code, possibly meaning African production, and used for all the vehicles they assembled regardless of brand. Holden uniquely used the second character of its series code instead of the model year number; I would suggest this was because Holden's series rarely followed the model year schedules but unlike Vauxhall and Opel based cars (majority of GMSA and GM do Brasil) they updated series codes in intervals between one and one and a half years (three plus for their HQ series) - Vauxhall and Opel retained the series code for the full generation of the vehicle e.g. FE Victor and Rekord D models each ran for the full 6 years of production regardless of any running changes to styling or specifications. GMSA's Holden based models however followed Holden's model years after 1971 (HG, HQ, HJ series - so G, Q, J respectively) but their other models used X from then onwards. GMSA also appended a suffix with up to three characters with letter codes for engine, transmission and one I'm unsure about.
For model years 1972 (NA) and 1973 (non NA - excluding Opel in Germany of course) the system was modified to shorten the model code to four characters, the second being a letter now indicating trim level. This made room in position five for an engine identifier which was specific to seemingly every variation (e.g. High versus Low compression versions of the same size engine). So for example what had been 80837 for a HQ series Holden Monaro GTS coupe with either a 253cid or 308cid V8 became 8Q37R (253) or 8Q37T (308). At this time Holden moved its series code to the end of their VINs, producing a 14 character version; this meant you could identify a model year 1974 HQ series car and a same year HJ series car - their PSNs continued through without resetting, having started at 100001 in early 1968. GMSA's suffix became up to four characters with the full series code (e.g. AQ, AC, AB, AH) and the codes for transmission and one I'm unsure about.
For model year 1973 the non NA divisions - excluding Opel in Germany - adopted a model year letter starting with C (D for MY74, E for MY75 through K for MY80 before resetting to A for MY81, B for MY82). Holden alone continued that pattern until it adopted the ISOVIN system.
As noted below North American divisions switched to the ISOVIN system for model year 1981; GM do Brasil in MY1983, Vauxhall and soon Opel whose operations were closely integrated by now started switching soon after, Holden from mid 1988, GMSA in the 2000s.
| Model Year | 1935 | 1955 | 1958 | 1960 | 1964 | 1965 | 1967 | 1968 | 1971 | 1972 | 1973 | 1981 | 1982 | 1987 | 1988 | 2003 |
| VIN pattern 1 | GM CA | GM CA | ||||||||||||||
| VIN pattern 2 | GM CA | |||||||||||||||
| VIN pattern 3 | Chevrolet (US) | |||||||||||||||
| VIN pattern 4 | GM CA | |||||||||||||||
| VIN pattern 5 | All GM (US) except Cadillac | GM CA | Vauxhall, Holden. GMSA, GM do Brasil (Opala) | Cadillac | ||||||||||||
| VIN pattern 6 | All GM (US) | Vauxhall, Holden, Opel US imports, GMSA, GM do Brasil (Opala + Chevette) | ||||||||||||||
| VIN pattern 7 (ISOVIN) | All GM (US), Opel? | Vauxhall, GM do Brasil | Holden | |||||||||||||
| VIN pattern 8 (ISOVIN) | All GM (US) | Holden |
VIN pattern 1: 10 characters. Year identifier (1 digit, YYYY), model code* (4 digits), sequence number (5 digits)
VIN pattern 2: 11 characters. Year identifier (1 digit, YYYY), model code* (4 digits), number of cylinders (1 digit: 6 or 8), sequence number (5 digits)
VIN pattern 3: 12 characters. Year identifier (1 digit, YYYY), model code* (4 digits), plant code (1 alpha character, Table 1), sequence number (6 digits)
VIN pattern 4: 11 characters. Year identifier (1 digit, YYYY), model code* (4 digits), plant code (1 alpha character, Table 1), sequence number (5 digits)
VIN pattern 5: 13 (17) characters. GM division code (one digit, Table 3), model code* (5 digits), year identifier (1 alphanumeric character, Table 2), plant code (1 alphanumeric character, Table 1), sequence number (6 digits)
n.b. Holden exclusively used the second letter of its series code instead of the year identifier.
n.b.2. GMSA exclusively added an A before the year identifier, and a suffix of up to 3 characters to indicate engine and transmission identifiers.
VIN pattern 6: 13 (14) characters. GM division code (one digit, Table 3), model code* (1 alpha character, 2 digits), year identifier (1 alphanumeric character, Table 2), engine code (1 alpha character, Table 2), (plant code (1 alphanumeric character, Table 1), sequence number (6 digits)
n.b. Holden exclusively added the second letter of its series code as a 14th character.
VIN pattern 7: 17 characters. WMI** (three alphanumeric characters), model code* (1 alpha character, 2 digits), year identifier (1 alpha character, Table 3), plant code (1 alpha character, Table 1), sequence number (6 digits)
VIN pattern 8: 17 characters. WMI** (three alphanumeric characters), model code* (1 alpha character, 2 digits), year identifier (1 alpha character, Table 3), plant code (1 alpha character, Table 1), sequence number (6 digits)
VIN pattern 9: 17 characters. WMI** (three alphanumeric characters), model code*** (1 alpha character, 1 digit), year identifier (1 alpha character, Table 3), plant code (1 alpha character, Table 1), sequence number (6 digits)
* Digit 1 is Division code Table 4. Digits 3 plus 4 are Fisher Body Codes, Table 6. In between character(s) indicate model level (some used to differentiate # engine cylinders)
** WMI 1st position is Assembly country, Table 5. 2nd position is Corporate id (G for GM, H for Holden prior to 2003, T for Toyota)
*** New body codes Table 7.
Table 1 (incomplete, also can depend on the operating period of each of the plants and the division they were in, i.e. "L" in later years meant "Elizabeth South Australia" for Holden built cars)
| 0 | Oshawa Ontario Canada Plant 1 |
| 1 | Oshawa Ontario Canada Plant 2 |
| 2 | St. Therese, Quebec, Canada |
| 4 | Scarborough, Ontario, Canada |
| A | Atlanta GA |
| B | Baltimore MD |
| C | South Gate, California |
| D | Doraville, GA |
| E | Linden, New Jersey |
| F | Flint, MI |
| G | Framingham MA |
| H | Fremont CA (1963-1964 Chevrolet) |
| J | Janesville, WI |
| K | Kansas City, MO |
| L | Los Angeles, CA |
| M | Lansing, Michigan |
| N | Norwood, Ohio |
| O | Oakland, CA |
| P | Pontiac MI |
| R | Arlington TX |
| S | St. Louis, Missouri |
| T | North Tarrytown Assembly (NY) |
| U | Lordstown, OH |
| W | Willow Run, MI |
| X | Kansas City, Kansas |
| Y | Wilmington, DE |
| Z | Fremont CA (1965-2010) |
Table 2
| US, Canada 1965-71 | Vauxhall 1967-82, Holden 1973-88, Opels in America 1973-5 | Brazil 1969-82 | |
| 5 | 1/9/65 - 30/8/66 | ||
| 6 | 1/9/66 - 30/8/67 | ||
| 7 | 7 | 1/9/66- 31/9/67 | |
| 8 | 8 | 1/9/66 - 31/9/68 | |
| 9 | 9 | 1/9/68 - 31/9/69 | |
| 0 | 0 | 1/9/69 - 31/9/70 | |
| 1 | 1 | A | 1/9/70 - 31/9/71 or 1/9/80 - 31/9/82 |
| 2 | 2 | B | 1/9/71 - 31/9/72 or 1/9/81 - 31/9/82 |
| C | C | 1/10/72 - 30/8/73 or 1/9/82 - 31/9/83 | |
| D | D | 1/9/73 - 30/8/74 or 1/9/83 - 31/9/84 | |
| E | E | 1/9/74 - 30/8/75 or 1/9/84 - 31/9/85 | |
| F | F | 1/9/75 - 30/8/76 or 1/9/85 - 31/9/86 | |
| G | G | 1/9/76 - 30/8/77 or 1/9/86 - 31/9/87 | |
| H | H | 1/9/77 - 30/8/78 or 1/9/87 - 31/9/88 | |
| J | J | 1/9/78 - 30/8/79 | |
| K | K | 1/9/79 - 30/8/80 | |
| A | A | 1/9/80 - 30/8/81 | |
| B | B | 1/9/81 - 31/9/82 |
Table 4
| 1 | Chevrolet |
| 2 | Pontiac |
| 3 | Oldsmobile |
| 4 | Buick |
| 5 | GMSA (Chevrolet versions of Holdens 1969-1972/3), GMC Sprint/Cabalero, GM do Brasil -1968-1982 |
| 6 | Cadillac |
| 7 | Canadian Pontiac |
| 8 | Holden |
| 9 | Vauxhall/Bedford |
| 0 | Opel (1973-5 US models only, GMSA Opel, from 1968) |
| C/K | Chevrolet trucks, GMC trucks pre 1972 |
| R | Delta era South African |
| T | GMC (trucks after 1971, Caballero after 1978) |
Table7 (incomplete)
| 1 | 2 door coupe |
| 2 | 2 door hatchback coupe |
| 3 | 2 door convertible |
| 4 | 2 door utility/pick up |
| 5 | 4 door sedan |
| 6 | 4 door hatchback sedan |
| 8 | Wagon |
| 9 | Limousine |