'67 option numbers

[Dave M.]

Can someone tell me why option code numbers have different sets of letters at the end . Example: On one original '67 Corvette Order copy the transmission option number reads 02M21AA. On a different original '67 Corvette Order Copy the transmission option number reads 02M21AB. There are numerous other option numbers that have different letters at the end also. Why is this? And what do these end letters mean?

As always thanks for your input.
Dave

[Joe L.]

Re: '67 option numbers

Dave-----

The 2 alpha character suffix code (sometimes it's just one letter) is called an "exception control letter" or "ECL", for short. The ECL, first used for the 1963 model year, is a code for variations of the same RPO which are necessary in order to make that option compatible with one or more other options. Primarily, the ECL code was a "tool" used by the assembly plant to enable workers to select the correct components to install on the car

For example, a 3.36:1 positraction axle unit installed in a 1965 Corvette had at least 2 variations; a unit with u-bolt yoke axle caps and a unit with cast iron axle caps. The former was installed on small block cars and the latter on big block. The ECL code is how the line worker knew which 3.36:1 differential unit to install in a particular car.

The above is a simple example I present to explain the system at its most basic level. In actuality, the system was quite complex.

[John H.]

Re: '67 option numbers

Dave -

There's a good discussion on the basics of the ECL system starting on page 43 of Noland's book.