posted by gloveboxoptions on December 1, 2021

This is the beginning of a four part series covering GM VIN and Model number format and usage from 1967 through 1972.

In Part 1 here, I cover GM Chevrolet and GMC Truck VIN and Model numbers for USA made vehicles.

The information contained in this series of articles gives more of a historical timeline account of GM VIN and Model coding styles. It does not go into listing all the specifics of each code in the VIN and Model numbers and what they stand for. For that, see our Blog article VIN Number Decode Diagrams. This article is a summary and recap of the research that went into making our YaVD VIN and Model Decoder and it is is meant to compliment that for a more thorough background with footnotes and References listed for further reading for the interested person.

1967-1972 Chevrolet Truck VIN & Model Information
Chevrolet VIN and Model is coding pretty simple and consistent in these years. A typical 1967 to 1971 Chevrolet Truck VIN looks like CS140F112233. This style is broken down and coded as:

[chassis][engine][gvwr][body][year][plant][6 digit serial]

It is interesting in that the only place I have found as of yet documenting how Chevrolet specified their VIN to begin with something that resembles a model number (i.e. "CS14" in CS140F112233, a format of [chassis][engine][gvwr][body]) was in the 1971 GMC Truck Service Manual1, which by the way, used a Chevrolet VIN number "CS141F110025" in its example component breakout explanation! and says this about the modified model number CS14:

"Series and model identification without second, third and fourth numbers."

Thus if this was a Chevrolet Model number of CS10934, then accordingly the modified model number becomes CS10934. Tack on the year 1, plant F, serial 110025 and you get CS141F110025.

1972 brought about a unified VIN format for both Chevrolet and GMC Truck divisions. This unified VIN retains the Chevrolet style VIN format but now includes the division code at the start of the Chevrolet VIN: "C" for Chevrolet and "T" for GMC Trucks. These VIN's now look like this: CCS142F223344 and TCE242F500001 respectively.

This style is broken down and coded as:

[division][chassis][engine][gvwr][body][year][plant][6 digit serial]

Chevrolet Truck Model Information
Like their VIN scheme, Chevrolet keeps a standard Model number coding format as did GMC. A typical and common 1967 to 1972 Chevrolet Model Number looks like this: CE10934. This style is broken down and coded as:


This format stayed constant throughout these years.

1967-1972 GMC Truck VIN & Model Information
While Chevrolet was consistent in the use of their VIN formats, GMC on the other hand, is a grab bag of differing VIN formats for 1967 through 1972.

Here is a list of example VIN styles used in each of the years:

1967: CM2590D C 1001                                   CM2590D PC1001B,  CM2590D P C1001B
1968: CM20DFB50001     CM20D FB50001,  CM20-FB50001
1969: CM20DBA50001     CM20D BA50001,  CM20-BA50001
1970: CS134-FZ50001    
1971: CE134-Z150001    
1972: TCS142F500001    
1967. Following a similar scheme as 1962-1966 GMC VIN's, for 1967 GMC placed the complete Model number CM2590D (in the 1967 example above) in the first half of the VIN, followed by the Assembly plant code P, Year C, 4 digit starting serial number 1001 that would roll into a 5 digit as production increased, and a GVWR code B. This style of VIN CM2590D PC1001B is found on the Serial Plate and the Protect-O-Plate.

To make things confusing, on the Service Parts Identification label, the VIN would be shown as CM2590D C 1001, which is missing the plant code P and the GWVR code B (unable to find any supporting documentation about this other than actual use). Freemont, California also produced GMC trucks in 1967 but I have never seen a Service Parts Identification label for one yet.

1968-1969. Years 1968 and 1969 brought about the complete Model number being removed from the VIN and in its place, a modified model number consisting of the Chassis, Engine, a shortened Series Code ("First and last numeric of model series"4,5,6) and a single character Body & Brake Code is used.

In the 1968 example shown above the truck Model number is CM2590D, the series is a 2500, and the new 1968 modified Model number is CM20D and the VIN is now completed as CM20DFB50001. The Series Code 20 in this VIN is derived from the Model series of 2500 using the first and last digit of the series: 2500

Of note is that in the USA GMC Parts book4,5,6 they refer to the shortened series code as "First and last numeric of model series". and not by some nomenclature. In the 1968-1969 GMC Service Manuals12,13 and the 1969 USA GMC Owner's and Driver's Manual11 it is referred to formally as "GVW Range" in their VIN decode. In the Canadian GMC Parts book7 it is referred to as "Abbreviated Model" for all 1968-1971 GMC VIN decodes.

See the section below for clarification on the Series and Body Style confusion in the VIN number for 1968-1969 as to the correct interpretation of 20D.

1970-1971. For 1970, GMC changed their Model number Body & Brake codes to that of Chevrolet. What was a GMC Fleetside Body & Brake code of 0D, now becomes Chevrolet's 34. And what used to be Model number CS1590D, is now Model number CS15934.

With the Model Body & Brake re-coding to that of Chevrolet, it also forces GMC to update the VIN number using the modified Model number to the current codes. The old modified Model number of CS10D now becomes CS134. Append onto the new modified Model number of CS134 the State Certification Code (more on that in Part 3) of "-", the Plant Code F, the Year Code Z, and a 5 digit serial number and you get CS134-FZ50001 for 1970 and 1971.

1972. Finally in 1972, GMC and Chevrolet created a unified VIN. This unified VIN is the Chevrolet style VIN with each company's division code prefixed to the VIN. GMC now codes their VIN like Chevrolet's i.e. TCS142Z500001. For GMC, the leading T represents GMC Truck division, C for Chevrolet. Note that you now need the Model number in order to determine what body style this used: Fleetside (34), Stepside (04), or other.

GMC Truck Model Information
A new Model number format is introduced for 1967: "A lettered prefix and 5-digit basic series numbering system is introduced for 1967 Truck model identification."3, i.e. CM2590D.

This style (same as Chevrolet) is broken down and coded like this:


This format stayed constant throughout these years.

Even though GMC used the same format for the Model number as Chevrolet, GMC had slight variations from Chevrolet in the codes themselves, of course.

The example below shows a common Model number for an identical Chevrolet and GMC truck (a LWB Fleetside Pickup half-ton):

Chevrolet 1967-1972 Model Number: CS10934
GMC 1967-1969 Model Number: CS1590D
GMC 1970-1972 Model Number: CS15934

The first difference between Chevrolet and GMC is in the Cab-to-Axle code. In the example Chevrolet uses the code 09 and GMC uses the code 59 to denote a 54"-59" Cab to Axle measurement. GMC added 50 to Chevrolet's Cab to Axle code, or else Chevrolet subtracted 50 from GMC Cab to Axle code to create theirs which begs the question as to why?.

The second difference is the Body and Brake code. Chevrolet would use a two digit code such as 34 while early GMC's would use a digit and an alphabetic letter 0D.

Then in 1970 GMC switched the Body and Brake coding to that of Chevrolet style, i.e. from 0D to 34, all the while keeping GMC's Cab to Axle codes (why not just change over to Chevrolet's Cab to Axle coding? they already changed to Chevrolet's Body & Brake codes).

1968-1969 GMC Confusion with Series and Body Code in the VIN Explained
As mentioned earlier, GMC in 1968 changes from using the full Model number in the VIN to using a modified model number coding in the VIN. If the Model number in 1967 was CM2590D, then the new modified model number for 1968 becomes CM20D. The proper way to breakdown and decode this modified model number is like this: [C] [M] [20] [D]4,5,6. This results in a two digit "Series Code" [20] and a one character Body code [D]. Here, as defined, [20] is the Series Code since it is derived from the model the Model Series 2500, but the often people will refer to this as the GVW Rating code. It doesn't help that GM series 20 and a GVWR code of "2" both refer to a three-quarter ton class of truck. It also does not help that GM for 1970-1971-1972 calls this code as the GVW Rating code so working backwards into earlier years you know the terminology as being the "GVW rating" from later years, not the series code. And this is where the mistake can easily be made when people decode the VIN. They will state the components as Series or (GVW rating) [2] and Body [0D] (a 1967 Model number resemblance), which is incorrect! This is more of semantics more than anything, because at the end of the day, no matter how you slice and dice it, whether it is reported accurately as Series 20 and Body D or inaccurately as Series (or GVW rating) of 2 and Body 0D, the end result is the same: you have a 3/4T pickup with a Fleetside box on it, LOL.

For 1970 and 1971, this confusion goes away completely since GMC changes their Body & Brake codes to that of Chevrolet, the new VIN is clearly distinct: CS134-ZZ50001, GVW Rating code [1] and Body & Brake code [34]. No more confusion.

Here is a quick recap that says it all about GVW Rating/Series and Body & Brake codes:

1967: CM2590DPC1001A GVWR = 2,    Body = 0D (Full and Complete Model Number in VIN "CM2590D")
1968: CM20DPB10001   Series = 20, Body = D  (Shortened from Series "2500", though technically Series, aka GVW Rating code in decodes)
1969: CM20DPA10001   Series = 20, Body = D  (Shortened from Series "2500", though technically Series, aka GVW Rating code in decodes)
1970: CE134ZZ54321   GVWR = 1,    Body = 34 (Abbreviated Model Number "134")
1971: CE134Z154321   GVWR = 1,    Body = 34 (Abbreviated Model Number "134")
1972: TCS142F123456  Series* = 1, Body = 4  (Abbreviated Model Number "14")
* = has mixed terminology: references to GVW Rating code2,9,8 and to Model Series (1500,150,15), "Series Designation", not GVW Rating code 8,9,10

Personal Observations
There is no manual I have encountered that will show and explain a complete decode of a 1967 GMC VIN like CM2590DPC100A describing the [P][C][1001][A] format nor the VIN used on the Service Parts Identification label.

In all the various GM 1967-1972 literature concerning VIN numbers and components it is noted that there are errors, missing or incomplete information, information only found in this manual, terminology used interchangeably, weird things that may be true but have yet to be seen in real life making it difficult to obtain a complete picture.

Given all that, one can say that there is quite a stark contrast between Chevrolet and GMC and it is interesting how each Division did their own thing. Hopefully the GMC coding style and its machinations (yes, that word was well chosen here!) all makes sense now. If I'm missing something here or you can add to this, please leave comments down below.

In Part 2, I cover Canadian VIN and Model numbers in the same way.
Part 2 the topic of Canadian Chevrolet and GMC VIN number and Model numbers were covered.

In Part 3, the topic discusses what a "K" VIN is and how it relates to the State Certification Code in the VIN for both Chevrolet and GMC.

In Part 4, I will list a quick and dirty summary of Parts 1, 2 and 3!

References to Footnotes in Article

Service Manuals:
1GMC Truck & Coach Division, General Motors Corporation, GMC TRUCK SERIVCE MANUAL Series 1500 thru 3500 Except "G" Models (Part No. X-7132, 10M 11-70, Pontiac, Michigan (C) 1970)
2GMC Truck & Coach Division, General Motors Corporation, GMC TRUCK SERVICE MANUAL Series 1500 thru 3500 Except "G" Models (Part No. X-7232, 10M 2-72, Pontiac, Michigan (C) 1972)
3General Motors Products of Canada, Limited, Oshawa, Ontario, 1967 GMC Truck Series 910-960 Shop Manual (Part No. PSD-53-130)
12GMC Truck & Coach Division, General Motors Corporation, GMC TRUCK SERIVCE MANUAL Series 1500 thru 3500 (Part No. X-6832, 12M 11-67, Pontiac, Michigan (C) 1967)
13GMC Truck & Coach Division, General Motors Corporation, GMC TRUCK SERIVCE MANUAL Series 1500 thru 3500 (Part No. X-6932, 12M 2-69, Pontiac, Michigan (C) 1969)
Parts Books:
4GMC Truck & Coach Division, General Motors Corporation, GMC Truck Master Parts Book MODELS CE,CM,CS,KE,KM,KS 1500; CE,CM,CS,KE,KM,KS 2500; CE,CM,CS 3500 (Part No. X-169001, September 1968)
5GMC Truck & Coach Division, General Motors Corporation , GMC Truck Master Parts Book MODELS CE,CS,EG,EM,ES 4500; CE,CG,CM,CS,EG,EM,ES,TE,TG,TM,TS 5500; CE,CM,ME,TE,TM 6500 (Part No. X-171009, 6M, October 1970 )
6GMC Truck & Coach Division, General Motors Corporation, GMC Truck Master Parts Book MODELS CE,CM,CS,KE,KM,KS 1500; CE,CM,CS,KE,KM,KS 2500; CE,CM,CS 3500 (Part No. X-172001, 5M,August 1976)
7General Motors of Canada Limited, Oshawa Ontario, 1962-72 Chev. & GMC TRUCK (LIGHT DUTY) Parts Catalogue No. 725A, Chev-GMC TRUCK (LIGHT DUTY) 1962-66 Series 10 thru 940; 1967-69 Series 10 thru 930; 1970-72 Series 10 thru 35 (December 1971)
Owner's Manuals:
8GMC Truck & Coach Division, General Motors Corporation, Owner's and Drivers's Manual Models 1500 thru 3500 (X-7200, Revised and Reprinted, 75M 12-69, Pontiac, Michigan)
9General Motors Products of Canada, Limited, 1972 Owner's and Driver's Manual Chevrolet Series 10-30 (ST 312-72, Part No. 6263138, First Edition, August, 1971, Oshawa, Ontario)
10General Motors Products of Canada, Limited, 1972 Owner's and Driver's Manual GMC Trucks Series 1500-3500 (Part No. 737094, Second Edition, January 1972, Oshawa, Ontario)
11GMC Truck & Coach Division, General Motors Corporation, Owner's and Drivers's Manual Gasoline Models 1500 thru 3500 (X-6900, Revised and Reprinted, 45M 8-68, Pontiac, Michigan)
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