Help to ID a my '67 M21

[R N.]

Hello everyone,

Ref. '67 L-79, M21, 3.70:1

After cleaning the road grime of the transmission I found all the numbers but need some help.

The metal tag attached by the bolt reads ?880853 and I assume it should be 3880853 but the first number is covered by the bolt. Is that the right tag # as looking in my reference material I see it listed for BB with 3.70:1 and 4.10:1 and not the L79.

The date stamp reads P7P027 which decodes to Sept 2nd, but what does the last "7" mean? Looking in Norland's book I see a few cars showing date codes with 5-digit date codes and some with 6-digits, it seems that all of the 6-digit date codes also end with a 7.

As always, thank-you.

[Jack H.]

Re: Help to ID a my '67 M21

Just flip your copy of the AIM open to the option section in the back and let your fingers walk the 4-speed transmission option, M20/21/22. Sheet A1 calls out the various transmission PN's that would appear on the tranny ID tag with 3880853 corresponding to a car equipped with L79 engine and M21 transmission.

[Jack H.]

Re: Help to ID a my '67 M21

On the 'extra' digit in the Muncie stamp, not much is said about this in NCRS literature because we don't specifically examine transmission ID numbers in Flight Judging. The Muncie build code was already there when the transmission sub-assy arrived at St. Louis, so it's not something you're going to see documented in the AIM.

The NCRS literature tends to hit the high points only in various JG books (date of assy) while often ignoring minor points. Consider this factory original Muncie stamping. Color balance is off, but it reads "P 03 ? 20" coming out of a car earlier than your '67 that saw a final assy date of mid-April.

If you study the ? character that's not discussed in the JG Books, it's a small '3' enclosed in a rectangular box. Some speculate it's a Muncie internal code for 3rd shift construction.

I'll wager Muncie used different coding schemes over the years with their sequence changing to improve source traceability for quality control. You'll need someone more familiar with the Muncie coding system to answer your question on the 'extra' digit...

[John H.]

Re: Help to ID a my '67 M21

We've seen the numerals 1,2,3, and 4 enclosed in a box on many Camaro Muncies - some by themselves, some as the last character in the Muncie "P-code"; most likely an inspector's stamp. Photo below is an original Muncie in a '67 Camaro.

[R N.]

Re: Help to ID a my '67 M21

Here is a picture of the date stamp - last digit could be 3 or 7.

[Wayne M.]

Re: Help to ID a my '67 M21

Here is a picture of the date stamp - last digit could be 3 or 7.

Kurt; others -- these final characters are probably asembler ID's. They have nothing to do with the date aspects of the assembly code.

If you follow most of these on eBay (a very large sample, BTW) sellers try to ascribe some significance to this final character -- worst case is those with a half-height character (like your "7"), but it's a square "c". So (you can guess what happens next) the seller claims M22, even before 21 Oct. 1968 (1969 model year) when the suffix coding "A, B or C" began.

So interpret your date stamping as P7P02, or a 4-spd trans assembled on Sept 2nd of 1966.