4th Generation Monte Carlo VIN Decoding

Updated: November 28th, 2001

• Federal law mandates that starting with the 1981 model year, all VIN numbers must be 17 characters long using alphanumeric characters (A-Z and 0-9). I, O and Q are not used in VIN numbers. The VIN must have the following make-up:
  • Positions 1 through 3 identify the country and manufacturer of the vehicle.
  • Positions 4 through 8 identify the vehicle information (car line, series, body style, type of safety restraint system used and engine type).
  • Position 9 is a check digit used to validate the VIN.
  • Position 10 is the model year of the vehicle.
  • Position 11 is the manufacturing plant.
  • Positions 12 through 17 are a sequencial number for the car line.
• There are a few locations on the car that the VIN number (or partial VIN) appear:
  • Left Side Dash at windshield (the obvious place)
  • On the engine block ID pad, behind the alternator, above the waterpump.
  • Optional engine block location, next to oil filter attachment point.
  • On the transmission, driver's side, above pan, toward rear
  • On the rear axle, (left or right side) adjacent to carrier
  • On the battery (the likelyhood that the original battery is still there is very remote)
  • On the alternator, top drive end frame
  • On the starter, outer case, toward rear
• The only way to tell a true 4th Generation (1983 - 1988) Monte Carlo SS from a non-SS by the VIN alone is to look at the 8th digit of the VIN. This is the Engine Code. In 1983, that digit MUST be a '7' for the car to be a true SS. For 1984 through 1988 models, the 8th digit MUST be a 'G'. This signifies the car came with the L69, 305ci, 5.0L High Output V8 engine. SSs came with no other engine. Period.
• The 6 digit sequence number assigned to the vehicle (VIN positions 12 through 17) does not indicate model style specific data. You can not compare this number with style specific production numbers to determine where your SS lies within the production of SSs that year. The sequencial number in the VIN contains SSs, CLs, LSs and plain model Monte Carlos (dependent on year) and possibly even other Chevrolet G-Body vehicles.
• 4th Generation Monte Carlo SSs were produced only at the Pontiac, MI and Arlington, TX production plants. Therefore, there are only two possible values (P, R) for the 10th VIN position. All 1983 to 1986 SSs were built in Arlington, TX. Roughly 75% of 1987 SSs were built in Pontiac, MI, the remaining 25% in Arlington, TX. All 1988 SSs were built in Pontiac, MI. All 86 Aerocoupes were built in Arlington, TX, while all 1987 Aerocoupes were built in Pontiac, MI.
• The 9th digit is the check digit. This is used to validate the VIN number. Possible values for the check digit range from 1 through 9 and the letter X. Each position in the 17 digit VIN has a numerical weight value assigned to it. The 9th (check) digit's position weight is 0, so it is mathmatically eliminated from the calculation. Each alphanumeric character also has a numeric weight. See the tables below for the numeric weight values for each character and position. The check digit is calculated as follows:
  1. Multiply the numeric weight of a VIN position by the numeric weight of the character present at that postion.
  2. Repeat for all 17 VIN positions
  3. Add up all values obtained in steps 1 and 2 above.
  4. Divide the total obtained in step 3 by 11.
  5. If the remainder of the division in step 4 is 10, use X as the check digit.
  6. Otherwise, use the remainder of the division (0 - 9) as the check digit.

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