It is the check digit and is calculated.
This is from wildjeff on the thirdgen.
http://www.thirdgen.org/techboard/history-restoration/511314-check-digit-calculation-anyone.html
Re: Check digit calculation, anyone remeber how to do it?
Yes, I have it on my decode page.
http://www.82firebird.com/82decoding.aspx
I also wrote a little app that you can use to find the check digit.
http://www.82firebird.com/downloads.aspx
Here it is though.
To determine the check digit you need to take the VIN and assign any letters in the VIN with the set numbers below:
A = 1, B = 2, C = 3, D = 4, E = 5, F = 6, G = 7, H = 8, J = 1, K = 2, L = 3, M = 4, N = 5, O = 6, P = 7, R = 9, S = 2, T = 3, U = 4, V = 5, W = 6, X = 7, Y = 8, Z = 9
Any numbers in the VIN remain the same and you will end up with a 17 digit number. Then multiply each of the 17 digits by a set "weight" (multiplier). The weight applied to each digit is as follows:
1st = 8, 2nd = 7, 3rd = 6, 4th = 5, 5th = 4, 6th = 3, 7th = 2, 8th = 10, 9th = 0, 10th = 9, 11th = 8, 12th = 7, 13th = 6, 14th = 5, 15th = 4, 16th = 3, 17th = 2
After multiplying each VIN digit by the associated weight - add up the results of all 17 products. Then divide by 11 and the remainder is your check digit.
If the remained is 10, then the check digit is 'X'.
Here's an example:
VIN = 1G1BL52P7TR115520 (note '7' is the check digit)
VIN 1 G 1 B L 5 2 P 7 T R 1 1 5 5 2 0
Assigned Values 1 7 1 2 3 5 2 7 7 3 9 1 1 5 5 2 0
Multiplier 8 7 6 5 4 3 2 10 0 9 8 7 6 5 4 3 2
Add the products: (1 X 8) + (7 X 7) + (1 X 6) ... (0 X 2) = 337 Divide 337 by 11 which gives you 30, and a remainder of 7 which is the same as the 9th digit of the VIN.
