differential codes

[Tim Scanlon]

Have a question about the above subject. I saw an ad for a Corvette for
sale and the seller had stated the rear end gear ratio(as stamped on the
diff.carrier or cover). Sorry if this is a dumb question, but is there
a code stamped somewhere identifying the ratio? Thank you in advance.

[Chris Burbage]

Re: differential codes

Yes, but they vary by year. My 65 has a 396 motor and 6 different rear axle codes. The diff on my car is AZ which would indicate a 3.55 ratio positraction rear. Of course there is no guarantee that someone didn't change out the gear set and then the code would not match the ratio. What year is the vette?

[Chris Burbage]

Re: differential codes

Yes, but they vary by year. My 65 has a 396 motor and 6 different rear axle codes. The diff on my car is AZ which would indicate a 3.55 ratio positraction rear. Of course there is no guarantee that someone didn't change out the gear set and then the code would not match the ratio. What year is the vette?

[Tim Scanlon]

Re: differential codes

Oops! Sorry Chris, and anyone else. I failed to post the year of my
car. It is a '70 L46, and according to the manual, most had 3:36 gears.

[Tim Scanlon]

Re: differential codes

Oops! Sorry Chris, and anyone else. I failed to post the year of my
car. It is a '70 L46, and according to the manual, most had 3:36 gears.

[Chris Burbage]

Re: differential codes

I don't have info for the 70 vette. For 71 I think the following is correct:
AA: 3.55
AB: 3.70
AC: 4.11
AD: 4.56
AW: 3.08
AX: 3.36

You might try putting the car in the air and turning the rear wheel one complete revolution. Count the revolutions of your driveshaft as you turn the rear wheel. Slightly more than three revolutions you have 3.08, three and a half + you have 3.55, etc.

Hope this helps.

Chris

[Chris Burbage]

Re: differential codes

I don't have info for the 70 vette. For 71 I think the following is correct:
AA: 3.55
AB: 3.70
AC: 4.11
AD: 4.56
AW: 3.08
AX: 3.36

You might try putting the car in the air and turning the rear wheel one complete revolution. Count the revolutions of your driveshaft as you turn the rear wheel. Slightly more than three revolutions you have 3.08, three and a half + you have 3.55, etc.

Hope this helps.

Chris

[Jeremy D.]

Re: differential codes

On the bottom of your rear differential housing, just towards the front of the car from where the leaf spring is, there should be a date stamping. Sometimes, you have to take a wire brush or something to scrape the goop off, but it should be there. For 1970 cars,there should be a "number for the shift that produced the unit, three letters that are the ratio code, the date produced(month 1-12/day/year/) and suffix letter for the plant that produced the differential."(NCRS '70-'72 Tech. Info. Manual and Judging Guide, 3rd Ed.)
Soooooooo...in order of appearance.....and I'm only listing the Positraction ratio codes because all Vettes had Positraction, they are:
CAM 3:36
CAO 3:70
CAT 3:08 (LT-1's, Auto's, Big-Blocks)
CAU 3:36 (LT-1's, Auto's, Big Blocks)
CAY 2:73
CAX 3:36 (LT-1's, Auto's, Big Blocks)
CAZ 3:55 (" ")
CFB 4:11 (" ")
CFC 4:56 (" ")

[Jeremy D.]

Re: differential codes

On the bottom of your rear differential housing, just towards the front of the car from where the leaf spring is, there should be a date stamping. Sometimes, you have to take a wire brush or something to scrape the goop off, but it should be there. For 1970 cars,there should be a "number for the shift that produced the unit, three letters that are the ratio code, the date produced(month 1-12/day/year/) and suffix letter for the plant that produced the differential."(NCRS '70-'72 Tech. Info. Manual and Judging Guide, 3rd Ed.)
Soooooooo...in order of appearance.....and I'm only listing the Positraction ratio codes because all Vettes had Positraction, they are:
CAM 3:36
CAO 3:70
CAT 3:08 (LT-1's, Auto's, Big-Blocks)
CAU 3:36 (LT-1's, Auto's, Big Blocks)
CAY 2:73
CAX 3:36 (LT-1's, Auto's, Big Blocks)
CAZ 3:55 (" ")
CFB 4:11 (" ")
CFC 4:56 (" ")