VIN Serial Number

[61hawk]

Would anyone know how the sequencing of the serial numbers went at the assembly plants?

For example the first 1965 C10 2 WD, Longbed built at the Atlanta plant would be: C1545A100001.

Would every vehicle after that be 100002, 100003, etc... regardless of build? Or would only those 1965 C10 2WD Longbeds at the Atlanta plant be assigned those numbers with things like short beds, 4WDs, etc... start with a new sequence starting with with 100001?

[61hawk]

May have just answered my own question. "Starting unit number is 100001 at each assembly plant regardless of series."

[Keith Seymore]

Within a series would count up one by one (ish):

Ie, each pickup would count up one by one regardless of wheelbase, box style, 2wd vs 4wd, etc.

Exceptions for assigning the serial portion:

If there are different nameplates going down the same line they might have unique starting points, ie, Chevy might start at 100001, GMC at 500001, Cadillac with 600001, etc.

Another exception: sometimes engine derivatives get a different starting point, for example V8 starts at 100001 but 6 cylinder starts at 600001.

Lastly - most plants have a series of buffers or accumulators so that vehicles can be sorted in order to level downstream workload (can't have too many manual trans in a row, can't have too many 4wd in a row, can't have too many tripowers in a row, can't have too many cab high running lights in a row) or to pull a vehicle aside for extended repairs. This also allows the final line to continue to run in the event of a breakdown in body shop or paint (which happens alot).

Typically that occurs after body shop before paint, and after paint before sending the unit down the final line, so two opportunities to shuffle the order from the way they were pulled/broadcast.

So - most vehicles don't come off the end of the line in a straight up one-after-one fashion in terms of serial number.

My analogy is that it is like writing checks: you pull the checks in numerical order but they don't necessarily clear the bank that way.

K

[Keith Seymore]

Even if they start at the same point each plant will count up at their own rate based on line rate (jobs per hour), production shifts (one, two or three), downtime (both planned and breakdowns), and overtime, independent of any other assembly plant. Therefore you can have the same serial portion from each plant.

So Atlanta might start at 100001 and Flint might also start at 100001, but it is the prefix portion (including plant code) that provides the uniqueness.

One time I was researching a GTO VIN 237375P115814 and it came back as "not a GTO".

After some time I realized that PHS mistakenly sent me the packet for 237375Z115814. Fremont vs Pontiac final assembly.

Took me about a year to figure out what was wrong, and why none of the option content on the paperwork matched the car I was looking at.

K

[VictoriaHardware]

Originally Posted by Keith Seymore

Within a series would count up one by one (ish):

Ie, each pickup would count up one by one regardless of wheelbase, box style, 2wd vs 4wd, etc.

I think this is evidence of that. This 1966 Fremont Plant (Z) VIN tag was stamped in two steps. The right side set of numbers were printed first. There was a stack of VIN tags created in a batch that went "6Z100001, 6Z100002, 6Z100003, ... So the operator at the VIN tag installation point in the plant had this stack pre-made. Each vehicle coming to him would get the next sequence tag. Before installing the tag, they would read the Build Manifest and stamp the correct left side numbers; in this case "C146".

That was what Fremont did. The red tag is from a 1965 Janesville (J) truck. They stamped the whole thing at once using the same stainless steel blank. An example of plants doing their own thing getting the same job done.