hemicudakidd

So i'm trying to decode the VIN on my 88 T/A GTA and the few sites that google throw up say for the 9th digit, 'CHECK DIGIT'.

I can understand this on 1 site because they may be checking their own information, but i have seen this on 3 sites now and i am wondering if anyone can shed any light on why these websites all say check digit for the 9th character in 3rd gen VIN's

Also, can anyone tell me if it is even possible to get a reproduction RPO code sticker, and if so, where to go?

Thanks in advance.....

Greg

mantaguy

iTrader: (5)

Here's a copy of how to decode your vin.,this is from a 86 FireBird Service Manual.As far as getting the SPID Sheet,I don't think you can get a reproduction.

JT

iTrader: (1)

It is a Check Digit that is used to validate the VIN as being accurate based on a formula. To us, it's not really useful as it won't tell you anything about the car itself.

There really isn't a lot of information that any online VIN site can disclose about your 1988 GTA - short of actually being able to poll the GM database and provide you with RPO codes associated with your VIN. Being a 1988 GTA, unless the car is a Canadian export, you won't be able to find any online website that can do that. All you'll be able to learn from the online VIN sites is basically what you probably already know (Trans Am/GTA or Firebird/Formula, engine, year and plant).

Regarding the SPID sticker, I don't believe there is any reproductions available - format wise. Even if there was a reproduction sticker available, there are no records available that can replicate the contents unless you can find the buildsheet.

eseibel67

SPID (RPO code) sticker would be difficult to reproduce because it's made of a plasticky material. As the value of 1980's cars escalates, someone will tool up to manufacture fraudulent stickers if they haven't already.

This is the formula for calculating the check digit from wiki. The purpose of the check digit is to verify that the VIN is real, and is not made up or copied incorrectly. Of course it's not foolproof, because anyone can do the math:

Check digit calculation[edit]

Check digit validation is compulsory for cars made in North America, as well as for all vehicles destined for sale in North America. It also may be used voluntarily by manufacturers who choose to do so for vehicle destined for markets where it is not required. In particular, it does not apply to vehicles, not destined for the North American market, produced by the following manufacturers: Citroën, BMW, Renault, Audi, Korean Chevrolets, Fiat and European Fords, among others.[http://en.wikipedia.org/wiki/Wikipedia:Citation_needed]
If trying to validate a VIN with a http://en.wikipedia.org/wiki/Check_digit, first either: (a) remove the check digit for the purpose of calculation; or (b) utilize the http://en.wikipedia.org/wiki/Zero-product_property in the weight to cancel it out. The original value of the check digit is then compared with the calculated value. If the two values do not match (and there was no error in the calculation), then there is a mistake in the VIN. However, a match does not prove the VIN is correct because there is still a 1 in 11 chance of any two distinct VINs having a matching check digit: an example of this would be the valid VINs 5GZCZ43D13S812715 (correct with leading five) and SGZCZ43D13S812715 (incorrect with leading character "S").
Transliterating the numbers[edit]

Transliteration consists of removing all of the letters, and substituting them with their appropriate numerical counterparts. These numerical alternatives (based on IBM's http://en.wikipedia.org/wiki/EBCDIC) can be found in the following chart. I, O and Q are not allowed, and can not exist in a valid VIN; for the purpose of this chart, they have been filled in with N/A (not applicable). Numerical digits use their own values.
Transliteration key: values for VIN DecodingA: 1B: 2C: 3D: 4E: 5F: 6G: 7H: 8N/AJ: 1K: 2L: 3M: 4N: 5N/AP: 7N/AR: 9S: 2T: 3U: 4V: 5W: 6X: 7Y: 8Z: 9
S is 2, and not 1. There is no left-alignment linearity.
Weights used in calculation[edit]

The following is the weight factor for each position in the VIN. The 9th position is that of the check digit. It has been substituted with a 0, which will cancel it out in the multiplication step.
Weight Factor TablePosition1234567891011121314151617Weight876543210098765432
Worked example[edit]

Consider the hypothetical VIN 1M8GDM9A_KP042788, where the underscore will be the check digit.
VIN1M8GDM9AKP042788Value14874491027042788Weight876543210098765432Products8 284835161218100 18560 2410282416

1. The VINs value is calculated from the above transliteration table, this number will be used in the rest of the calculation.
2. Copy over the weights from the above Weight Factor Table.
3. The products row is a result of the multiplication of the vertical columns: Value and Weight.
4. The products (8,28,48,35..24,16) are all added together to yield a sum of 351
5. Find the remainder after dividing by 11
   351 http://en.wikipedia.org/wiki/Modulo_operation 11 = 10
   351 ÷ 11 = 31 10/11
6. The remainder is the check digit. If the remainder is 10 then the check digit is X. In this example the remainder is 10, so the check digit is transliterated into X.

With a check digit of 'X' the VIN: 1M8GDM9A_KP042788 is written as: 1M8GDM9AXKP042788.
Straight-ones (seventeen consecutive '1's) will suffice the check-digit. This is because a value of one, multiplied against 89 (sum of weights), is still 89. And 89 divided by 11 is 8 with the remainder being the fraction "1 over 11," thus 1 is the check digit. This is an easy way to test a VIN-check algorithm.