C2 -1966 Transmission I.D. Tag Numbers

[R N.]

I received Noland Adams (Vol. 2) book for Christmas and I am enjoying it. I recommend this book to everyone who doesn't have it) After reading the '66 section and looking at the survey results for the transmissions, I have noticed some discrepancies with correct transmission I.D. tags.

Most of the reference supplied (including Noland's book) show the following I.D. tag numbers. (1966 models)

3880853 M21 with L79 (327/350HP)
3880855 M21 with L36 & L72 (427/390/425HP)
3870354 M20 with wide radio

There are serveral cars listed in the survey with M20's but they have ID tag
# 3880853 which was for the C.R. M21.

This brings the question, how accurate were the tags installed onto the cars? I'm sure an assembly worker on the line back in '66 didn't care too much if he accidently placed the wrong tag on a car.

Can anyone please shed some light in this area for me as my L72 seems to have an incorrect tag on it.

As usual, thank you for your assistance.

[John H.]

Re: C2 -1966 Transmission I.D. Tag Numbers

Kurt -

The embossed metal tag with the transmission part number on it was installed at Muncie when the transmission was assembled, not at St. Louis; it's almost unusual to see one any more (other than the recent reproduction tags), as it's usually the first thing the transmission rebuilders throw away, and there aren't many 35-40-year-old Muncies that haven't been rebuilt at least once.

[Joe L.]

Re: C2 -1966 Transmission I.D. Tag Numbers

Kurt-----

The primary purpose for the different Muncie trans part numbers related to the installed speedometer gears (drive and driven). Otherwise, the M-20, M-21, and M-22 for any particular model year were the same.

The information provided in the AIM and other references is not complete or, necessarily, accurate with respect to which part number(s) could have been used for any specific application.

For example, the AIM might specify a certain transmission part number for, say, an L-36 with M-21. However, depending upon the rear axle ratio, there had to have been at least 2 different part numbers for the transmissons used for this application even if only the speedo DRIVE gear possibilities is considered.

[Wayne M.]

1966 Transmission Tag Confusion

Think of the tranny tags as only being indirectly related to the engine option.

Rather, the tag is to identify if the trans is wide or close ratio, and,if close ratio, is the drive gear on the mainshaft tail suited for the low numerical differential ratios (3.08, 3.36, 3.55) or the higher ones (3.70, 4.11) [Let's ignore the 4.56 for this discussion].

So there are 3 possibilities [let's also ignore the M22 possibilities]; base engines and wide ratio L79's should use the 3870354; L79's with the close ratio, and L72's with the mandatory close ratio, but 3.70 or 4.11 rear should use 3880853, and L72's with the 3.55 "general purpose" or lower numerical ratios shold use 3880855. L36's with the wide ratio should use the "354". Were L36's available with the close ratio ? if so, same trans #'s as for L72's, depending if high and low numerical rears.

[R N.]

Re: C2 -1966 Transmission I.D. Tag Numbers

Thanks Joe:

This info you have told me clears up some things about the vague information of tags. My L72 has the 3880853 tag which is for L79 & M21. It should be 3880855. My rear is a 3.70 I guess as long as this item is not judged I should be OK. It's just that most people (myself included) go by whats in the book and not the known facts. Like John said there are not many original tags around, however, I feel this is an original tag and hense I posted the question.

[R N.]

Re: 1966 Transmission Tag Confusion

Wayne:

Thank you for your info. My '66 is a L72 with a 3:70 rear ratio. If I read correcly what you have told me, the 3880853 is the correct tag number for this engine/trans./rear combination?

[Craig S.]

Re: 1966 Transmission Tag Confusion

Kurt - for what it's worth, my verified original 67 L79 M20 wide ratio transmission has the 853 tag like Noland's book states....but I can't prove for sure it came that way as I am not the first owner. However, the tranny is the original to the car, unless the tag was changed along the way...but I doubt it...Al Grenning verified it and the engine pad.....Craig

[Dan A.]

Re: 1966 Transmission Tag Confusion

Hi Wayne, it's been a while.

My '66 L36 has a close ratio with an 853 tag that I believe to be the original tag. Car has a 3:70 gear.

[John H.]

Re: 1966 Transmission Tag Confusion

My '67 327/300/M20 (standard 3.36 axle) has the original trans, and what appears (based on its scruffy condition) to be the original tag (3870354), which is the transmission assembly part number shown in the A.I.M. for the base engine/standard axle configuration.

[TL Wright]

Re: 1966 Transmission Tag Confusion

I am in the process of trying to figure out what ratio rear I have and what transmission. My 66 was sold to me as originally being an L79. While the original block(not in the car) is not really verified to my liking, the transmission tag is a 3870354. It does appear to be original. And the transmission appears to be original as well. Is there some method I can use to figure out the rear ratio? and to verify the wide/close ratio?

[TL Wright]

Re: 1966 Transmission Tag Confusion

John
I am trying to figure out my axle ratio. Can you tell me a way to check or maybe what your engine tachs at certain speed so I can see how it compares?
TL