1967 Rear Axle Ratio Codes - Discrepancy?

[Rocco S.]

I am preparing my 1967, un-restored coupe for its first chapter flight judging in a few weeks. I have been reviewing my 2016, 6th edition "Technical Information and Judging Guide" and noticed a possible discrepancy on Table C-4 Rear Axle Ratio Codes.

My car has an L79 (327-350 HP), K66 (TI), M21 Close Ratio trans and 3.70:1 positraction rear. The ratio code stamped on the housing is "FA". This is confirmed by both the Tank Sticker and the Shipping Manifest ECL Code "2G81FA".

This is a somewhat odd combination since the car also has A/C.

According to Table C-4 the "FA" 3.70:1 positraction rear with 4-speed was only available with the 427 engine.

My car is a one-owner car and was parked in 1974 with only 53K miles so I know it has the original rear and have the documentation to prove it.

Will this issue present a problem in judging? Can it be that the car is an anomaly/ special order? Could the table in the judging guide be incorrect?

Comments are welcome. Thank You

[Keith B.]

Re: 1967 Rear Axle Ratio Codes - Discrepancy?

does it have the bolted end caps

[Rocco S.]

Re: 1967 Rear Axle Ratio Codes - Discrepancy?

Sorry, I forgot to say that it has U-Bolts not the caps used on Big Blocks

[Donald A.]

Re: 1967 Rear Axle Ratio Codes - Discrepancy?

The differential assembly date and code stamps are not judged Rocco. On page 207 in the Chassis Section of the 67 Judging Guide 6th edition is the following quote: "Judging Guidance: the following information is not judged, however it is provided for reference. The differential casting..." At my chapter meet a few years ago my 67 differential was not judged regarding differential date/code stamps. I now have a '66 and just took it to my Chapter judging and again, no evaluation was made of the differential date/code stamps. Maybe things have changed and I do not have the newer 67 Guide but to my understanding, you are fine, the FA stamp on your car will not be judged. Also just my opinion, but the FA code is big block only and I think it more likely that you are misreading the stamp or that someone changed that differential in the past 50 years! Good luck at your judging event and have fun.

[Mike E.]

Re: 1967 Rear Axle Ratio Codes - Discrepancy?

The differential assembly date and code stamps are not judged Rocco. On page 207 in the Chassis Section of the 67 Judging Guide 6th edition is the following quote: "Judging Guidance: the following information is not judged, however it is provided for reference. The differential casting..." At my chapter meet a few years ago my 67 differential was not judged regarding differential date/code stamps. I now have a '66 and just took it to my Chapter judging and again, no evaluation was made of the differential date/code stamps. Maybe things have changed and I do not have the newer 67 Guide but to my understanding, you are fine, the FA stamp on your car will not be judged. Also just my opinion, but the FA code is big block only and I think it more likely that you are misreading the stamp or that someone changed that differential in the past 50 years! Good luck at your judging event and have fun.

He indicates that he has the tank sticker and shipping manifest indicating FA. Unless I am missing something, that would tend to preclude either misreading or replacement.
However, I don’t have an answer for him.

[Larry M.]

Re: 1967 Rear Axle Ratio Codes - Discrepancy?

The Exception Code Letter (ECL) used for the Rear Axle Ratio on the tank sticker does not mean it is the same as the "axle code" that is stamped into the rear axle housing.

Example is my own 1967 lo-mile car. It has a L-79 engine with AC and a wide ratio 4-speed. The ECL for the 3.36 posi rear is CA. That is also what my tank sticker states. However the factory installed positraction gear ratio for this combination is AM which is stamped on the rear axle housing.

For the OPs car, the ECL on the tank sticker for a L-79 with close ratio transmission and AC is FA and signifies a 3.70 ratio. The correct factory stamped rear axle code for a 3.70 posi for the small block cars is AO. This is what it should have left St. Louis with. OP needs to check what is stamped on the existing housing. If different from AO, it is likely a replacement. I would also check the date, as it should be close to the car build date.

A rear axle housing actually STAMPED FA would be a 3.70 positraction rear for a big block car and would also have the bolted end caps. The ECL (tank sticker or window sticker) for this combination would either be NA or YA depending on transmission type (manual or auto).

Hope this helps.

Larry

[Rick A.]

Re: 1967 Rear Axle Ratio Codes - Discrepancy?

Agree with Larry completely

[Rocco S.]

Re: 1967 Rear Axle Ratio Codes - Discrepancy?

Thank you Larry. Your explanation is right on and exactly what I found. I looked at the stamped code and found "AO" 3.70: Posi small block. I guess I was confused when I looked at the ratio code table and compared with my Tank Sticker and Shipper Manifest, both which had an ECL of 2G81FA. So there is no correlation between the ECL number and the actual stamped ratio code. Learned something today which is a good thing. Thanks again.