1962 rear axle identification code for ratio.

[Philip M.]

Hi, New guy. I have a 1962. The rear axle has the vent tube, drain plug tag saying it is a posi track. Looking from front to back the the 10 bolt cover has the following codes between the 2 and 4 o'clock bolts on the drivers side "3789812" "L201" and a skinny "P". On the passenger side between the 8 and 10 o'clock bolts it is stamped "AM112". It is my understanding that on the shaft towards the passenger side rear tire there should be a two letter code that if correct should start with a "C" and end with another letter to indicate the ratio. There is no metal tag on the 1 o'clock bolt. Could it have just been left off by mistake or am I looking in the wrong place for this two letter code
I cannot fine that two letter code. The axle is very clean and a lightly brushed it but I cannot find the code. Any help would be appreciated or a photo of the location would be greatly appreciated.
Thank you, Phil M

[Mike E.]

Re: 1962 rear axle identification code for ratio.

Phil,
The AM is the two-letter code you are looking for. That is a passenger car code. The unit was cast on December 20, 1961, and assembled on January 12 (1 12). The ratio tag is missing because the unit has been replaced at some point.

[Tom P.]

Re: 1962 rear axle identification code for ratio.

Hi, New guy. I have a 1962. The rear axle has the vent tube, drain plug tag saying it is a posi track. Looking from front to back the the 10 bolt cover has the following codes between the 2 and 4 o'clock bolts on the drivers side "3789812" "L201" and a skinny "P". On the passenger side between the 8 and 10 o'clock bolts it is stamped "AM112". It is my understanding that on the shaft towards the passenger side rear tire there should be a two letter code that if correct should start with a "C" and end with another letter to indicate the ratio. There is no metal tag on the 1 o'clock bolt. Could it have just been left off by mistake or am I looking in the wrong place for this two letter code
I cannot fine that two letter code. The axle is very clean and a lightly brushed it but I cannot find the code. Any help would be appreciated or a photo of the location would be greatly appreciated.
Thank you, Phil M

Phil,
As mentioned, the CASTING date on the driver side of the case translates to Dec (L) 20, 1961.
On the passenger side, the STAMPED letters/numbers translates to a passenger car rear (AM=3.36 posi) (112=Jan 12). The year is NOT stamped into the case because the year is part of the CASTING date on the driver side.
Thus, your rear was CAST in Dec 61 and ASSEMBLED in Jan 62, then it was installed in a 1962 FULL SIZE Chevrolet passenger car-----------------most probably late Jan/early Feb.

Below are the rearend gear ratio tags (they DO NOT denote posi or non-posi, only the gear ratio!!!) which were (or should have been) installed under the 2 o'clock nut (as you face the rearend). They are all available as reproductions from the Corvette/Chevy vendors.
THE ILLUSTRATION BELOW IS THE CORRECTED VERSION!
NOTE-ATTENTION, FINALLY, NCRS has acknowledged that the 3.36 and 3.55 tags, in the vendors catalogs, were WRONG! As shown in the illustration below, the CORRECT 3.36 tag has ONE hole and the 3.55 tag has TWO holes. SOOOOOOOOOOO, if you order a repo tag for your 3.36 posi, order the one with only one hole.

Now, with all of that said, unless you are absolutely determined to have a rear with the correct stamped 2-letter code on the passenger side, and if your rear is working fine, I'd keep it. Good posi rears (with the correct stamped code) are becoming hard to find--------------AND EXPENSIVE! If you have the car judged-------------------------and if a judge even looks at the stamped code---------------------------the point deduction will be minimal. Other than the AM, everything about your rear is correct for your car.

[Joe M.]

Re: 1962 rear axle identification code for ratio.

Tom, would the reference tags above also work for a 1960 rear differential? My 1960 has a PG tranny and the differential cover has AE 11 02 (3:55, November 2) stamped on the passenger side. The driver side has a casting date of J39 (October 3, 1959) and the correct part number, 3725899. The gear ratio metal tag only has one hole, the hole that the stud goes through. In the table above, that tag would be for a 3:36 set of gears.

The pinion gear is dated 9 59 and the ring gear is dated 10 59; so I believe the differential is original to the car.

[Tom P.]

Re: 1962 rear axle identification code for ratio.

Those tags were used 57-62 (-64 on pass cars). There seems to be some uncertainty as to whether they were also used on 56 cars (and 55 pass cars).
According to Ken Kayser, ALL the 55-57 ratio tags were solid (except for the single hole) and the gear ratio was ink stamped on the tag (number of pinion and ring gear teeth). I personally have not seen any of these very early tags with the ink stamped numbers (NOT to dispute Ken).
Now, with all of that said, the 62-earlier Corvettes DID NOT have a data plate affixed to the body (ala 63-later cars) which provided information about color, accessories, etc. They only had a VIN plate. Thus, any 62-earlier car could have any engine, transmission, rearend (posi or non-posi), color, accessory, etc, etc, without anything to identify what was on the car---------------------EXCEPT THE ORIGINAL PAPERWORK.
My whole point is that you can put any rearend in a 57-62 car (that was available during those years) and there is no way to confirm or dispute if it is the original rearend (of course, as long as it has the correct codes). Also, of course, the 53-55 cars ONLY had a 3.55 and the 56 cars ONLY had a 3.70(3sp) or a 3.55(PG), and supposedly a 3.27-----------------but I've NEVER seen a real 56 3.27. Also, a VERY TINY handful of 56 cars (supposedly) got a posi (Hitorque-maybe in the Sebring racers), but I've never seen one of those either. I'D LOVE TO GET MY HANDS ON ONE-----------------or see some pictures.

[Dino L.]

Re: 1962 rear axle identification code for ratio.

Hope these pictures help, Posi for a November built 1962

[Tom P.]

Re: 1962 rear axle identification code for ratio.

I see the original DANA posi unit has been replaced with a late model Eaton unit.

[Dino L.]

Re: 1962 rear axle identification code for ratio.

Tom....you are the man and you are correct.....I could have never rebuilt the rear end without your help.....your advice on axles and bearings were indispensible...you know your stuff!!!

how do you like an original 340HP 327 stroked to 383 Cu In, with a wide ratio T10, and a 3:55 gear? should make for a nice driver?LOL

[Tom P.]

Re: 1962 rear axle identification code for ratio.

If your engine has the original AFB, you MIGHT want to go to a slightly larger Holley. I think you would notice a performance improvement. That AFB may not be enough to feed a 383. But then that would also require changing to a 461 style manifold. Oh well---------------------as is, it certainly will be a super driver!
My 56 with the SB400 is done by 5500 because the single air meter FI just will not provide enough air to feed the 400.

[Rod K.]

Re: 1962 rear axle identification code for ratio.

Tom, (There seems to be some uncertainty as to whether they were also used on 56 cars...)

A few years ago I saw a complete '56 (per the casting date) pass car axle, drum to drum, which had the full round tag in place blacked out so I couldn't confirm the ink stamping. The complete axle appeared unmolested. Just one data point.

[Tom P.]

Re: 1962 rear axle identification code for ratio.

---------------------------------------------------

A few years ago I saw a complete '56 (per the casting date) pass car axle, drum to drum, which had the full round tag in place blacked out so I couldn't confirm the ink stamping. The complete axle appeared unmolested. Just one data point.

And that fits perfectly with what is in Ken Kayser's book.
In the past, I have visited MANY salvage yards (not much in recent years). I clearly recall seeing the various versions of discs (at 2'oclock position) on pass car rearends. But back in those days, I was not knowledgeable as to their purpose or meaning. When I removed the rearend center sections from cars in salvage yards, I simply let the discs drop on the ground. I remember cussing some of them because they cut my fingers! Also, the retaining nuts on those rearends changed from 57 to 58. The 55-57 rears had nuts with copper sealing washers under them. The 58-64 cars had nuts with swedged-in integral flat steel washers. I also let them drop to the ground. GOD, I wish I had saved all of those 58-64 style nuts/washers! They are NOT available now!

[David B.]

Re: 1962 rear axle identification code for ratio.

Those tags were used 57-62 (-64 on pass cars). There seems to be some uncertainty as to whether they were also used on 56 cars (and 55 pass cars).
According to Ken Kayser, ALL the 55-57 ratio tags were solid (except for the single hole) and the gear ratio was ink stamped on the tag (number of pinion and ring gear teeth). I personally have not seen any of these very early tags with the ink stamped numbers (NOT to dispute Ken).
Now, with all of that said, the 62-earlier Corvettes DID NOT have a data plate affixed to the body (ala 63-later cars) which provided information about color, accessories, etc. They only had a VIN plate. Thus, any 62-earlier car could have any engine, transmission, rearend (posi or non-posi), color, accessory, etc, etc, without anything to identify what was on the car---------------------EXCEPT THE ORIGINAL PAPERWORK.
My whole point is that you can put any rearend in a 57-62 car (that was available during those years) and there is no way to confirm or dispute if it is the original rearend (of course, as long as it has the correct codes). Also, of course, the 53-55 cars ONLY had a 3.55 and the 56 cars ONLY had a 3.70(3sp) or a 3.55(PG), and supposedly a 3.27-----------------but I've NEVER seen a real 56 3.27. Also, a VERY TINY handful of 56 cars (supposedly) got a posi (Hitorque-maybe in the Sebring racers), but I've never seen one of those either. I'D LOVE TO GET MY HANDS ON ONE-----------------or see some pictures.

Tom.
This could be your lucky day. Have owned several '56 Hi Torque units and have old photos I took at the time. They in fact were used at '56 Sebring with a multitude of different gear ratios. I had a 4:56 unit (with photos, car came out of Tech Center) and there was a 3:70 in the Sebring car I also owned (photos as well). There seems to be a lot of confusion re: the rear end tag thing. The full size tag WAS stamped with the gear ratio but will refrain from further comment. Do have the Engineering blue print showing tag size, and ink dimension etc.
regards,

[Tom P.]

Re: 1962 rear axle identification code for ratio.

I'd love to see pictures of a real Hi Torque posi.

[David B.]

Re: 1962 rear axle identification code for ratio.

Where would you like me to forward?
Incidentally, GM production records indicate there were 155 '56 Corvettes produced with the 3.27 gear ratio. The breakdown was:
RPO 471-A 154 RPO 471-B 1

[Tom P.]

Re: 1962 rear axle identification code for ratio.

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