Updated rear end codes page

https://www.g3gm.com/Chevrolet-Rear-End-Codes-h25.htm

^^^I only updated on the Chevrolet page for now since this is just generic info. Expect all pages to be updated once I start finding out which gears were available for specific years & models. Possibly this could help out some of you guys that want to pop the covers & count your teeth.

Here's some more stuff to read up on:

Rear Axle Identification and Decoding
Identify the gear ratio, the build date, the plant where it was assembled the work shift when it was assembled, and positraction source - if equipped. This number is stamped on the forward facing passenger side axle tube. It'll usually be about 3 inches away from the carrier housing (center section of rear end housing).

This stamp can be difficult to locate on an 30+ year old axle due to layers of paint, undercoating, grease, and dirt. It may be necessary to partially strip the forward face of the passenger side axle over the middle third of the length in order to locate and discern the characters. A razor blade and/or putty knife, fine wire brush, and cleaning solution may be needed tools in this search.

Rear Axle Code example: CB G 112 1 E
(CB = Ratio, G = Plant, 112 = 112th day of year, 1 = shift, E = Positraction Source)

Assembly Plant Codes
Buick - B
Buffalo - C
Cadillac - D
Detriot Gear & Axle - G
GM of Canada - K
Warren, MI - W
Oldsmobile - O
Pontiac - P
Pontiac/Canada - M

Shift: D or 1 = Day shift| N or 2 = Night shift

Positraction Source/Code:
- = No positraction
D = Dana Positraction Differential
E = Eaton Positraction Differential
G = Chevrolet G&A Positraction Carrier
O = Oldsmobile Positraction Carrier
W = Warren/Warner Motive

Positraction Casting Numbers
Due to the possible confusion with gear ratio descriptions... a HIGHER number is a LOWER gear.
In the below examples, 2.56:1 & down = 2.41, 2.56, etc... which is actually a HIGHER gear ratio.

8.5" "Corporate"
Casting # Series Gearing
410408N 3 2.73:1 & up
410409N 2 2.56:1 & down

rear axle casting date code Rear Housing Casting Date

Example: D143 - (D = Month, 14 = Day, 1 = Last digit of year (1973)).

Month: A = Jan, B = Feb, C = Mar, D = Apr, E = May, F = Jun G = July, H = Aug, I = Sep, J = Oct, K = Nov, L = Dec

OK so does anyone have a book to tell what codes are what for the first two - three digits? Here's what I mean:

Rear Axle Code example: CB G 112 1 E
(CB = Ratio, G = Plant, 112 = 112th day of year, 1 = shift, E = Positraction Source)

Where would you find the actual ratio codes? I can't find anything in my books. Not even some of my old manuals from the 70's have these codes. I looked around the net even to see if this information is posted but I guess not.

I'm personally looking for two codes, one being ACC & the other is CFC or possibly GFC? If it's GCF, then I'm looking at a 4.56 posi from a Corvette by one internet source & I know that ain't right. Yeah I know that I can pop it open & find the current gear ratio, but this is for informational purposes only in case someone is restoring their ride & wants to find out original gearing, etc.

If anyone knows where to source these codes or even a book that I can buy if I have to, then great. I'd like to get these up on the homepage.

cool thanks for updating

Rear Axle Identification & Decoding
Identify the gear ratio, the build date, the plant where it was assembled the work shift when it was assembled, and positraction source - if equipped. This number is stamped on the forward facing passenger side axle tube and It'll usually be about 3 inches away from the carrier housing (center section of rear end housing).



8.5" "Corporate"

Casting # ........... Series ............. Gearing
410408N .............. 3 ............. 2.73:1 & up
410409N .............. 2 .............. 2.56:1 & down


Axle Ratio Tooth Combination
2.56:1......... 41,16
2.73:1......... 41,15
3.07:1......... 43,14
3.08:1......... 40,13
3.08:1......... 37,12
3.31:1......... 43,13
3.36:1......... 37,11
3.42:1......... 41,12
3.55:1......... 39,11
3.73:1......... 41,11
4.10:1......... 41,10
4.11:1......... 37,9

Already had all of that stuff posted Limey. I need to find out the actual codes. See where that "CB" is on your picture? What gear ratio is that? I have one more book to wipe the dust off of & look through. Hoping it has them, but if not maybe an old service manual might?

i should i have them for chevy only tho

That's fine. If I'm correct, they shouldn't be classified by brand, but by body style. F Bodies, X Bodies, & Corvettes all have different codes & are easy to find on the net. The codes should be A Body specific & will denote (sometimes) which brand it was designated to in the coding. Even 64-72 codes are out there. It just seems we are left in the dark once again.

Rago wrote: See where that "CB" is on your picture? ?

that is an example of what it looks like on the axle tube

I know. Here's what I'm trying to find & create for our cars:

http://www.chevy-camaro.com/parts/chevy-camaro-part-codes-axle.htm
http://www.chevellestuff.com/1971/rear_axle.htm

Bottom of page is another example & is the only place that I have found one of my stampings. I know mine's not a 12 bolt with 4.56 posi from a Corvette though:
http://www.oldride.com/library/1970_chevrolet_corvette.html

They are all over for early cars, but not ours.

well get on it man I will look to see if I can dig anything up as well

ive got all the rear end codes by year. ill get them posted up when I got time.

1973
first 2 letters
2.73..............WA
2.73..............AC
2.73 posi........XB
2.73 Posi........CC
3.08..............WC
3.08..............AD
3.08 Posi........XC
3.08 Posi........CD
3.42..............WE
3.42...............AJ
3.42 Posi.........XE
3.42 Posi.........CJ

3rd letter
Buick.....................................B
Buffalo...................................C
Chevrolet Gear and Axle.............G
GM of Canada...........................K
Warren....................................W
Oldsmobile................................O
Pontiac....................................P
Pontiac/Canada.........................M



1974
first 2 letters
2.73..............AC
2.73..............CC
2.73..............WB
2.73 Posi........XA
3.08..............AD
3.08 Posi........CD
3.08..............WC
3.08 Posi........XC
3.42..............AJ
3.42 Posi........CJ
3.42..............WE
3.42 Posi........XE

3rd letter
Buick.....................................B
Buffalo...................................C
Chevrolet Gear and Axle.............G
GM of Canada...........................K
Warren....................................W
Oldsmobile................................O
Pontiac....................................P
Pontiac/Canada.........................M



1975
first 2letters
2.56 posi........CH
2.56..............AH
2.73..............WA
2.73posi........XA
2.73posi........CC
2.73..............AC
3.08..............WC
3.08 posi........XC
3.08 posi........CD
3.08..............AD
3.42..............WE
3.42 posi........XE
3.42 posi........CJ
3.42..............AJ

3rd letter
Buick.....................................B
Buffalo...................................C
Chevrolet Gear and Axle.............G
GM of Canada...........................K
Warren....................................W
Oldsmobile................................O
Pontiac....................................P
Pontiac/Canada.........................M

1976
FIRST 2 LETTERS
2.56 POSI........CH
2.56 POSI........AH
2.73...............WA
2.73 POSI........XA
2.73 POSI........CC
2.73...............AC
3.08...............WC
3.08 POSI........XC
3.08 POSI........CD
3.08...............AD

3rd letter
Buick.....................................B
Buffalo...................................C
Chevrolet Gear and Axle.............G
GM of Canada...........................K
Warren....................................W
Oldsmobile................................O
Pontiac....................................P
Pontiac/Canada.........................M

1977
FIRST 2 LETTERS

2.56.............AB
2.56 POSI.....CB
2.73.............ZE
2.73.............AC
2.73 POSI.....ZW
2.73 POSI.....CC
3.08.............ZJ
3.08.............AF
3.08 POSI.....ZY
3.08 POSI.....CF

3rd letter
Buick.....................................B
Buffalo...................................C
Chevrolet Gear and Axle.............G
GM of Canada...........................K
Warren....................................W
Oldsmobile................................O
Pontiac....................................P
Pontiac/Canada.........................M

Awesome! That's exactly what I was looking for. I'll get to updating the homepage data.

Finished! Everyone check it out & let us know what you think.

https://www.g3gm.com/Chevrolet-Rear-End-Codes-h25.htm

dude that rocks but you stole my Picture LOL No seriously a good job by the involved parties

looks good dude, thanks for getting that stuff updated. im slacking pretty bad
Any a book i recommend is "Chevrolet by numbers" Chevelle & El Camino
but I did find the first screw up in the book, which is on 1973 Chevelle and the Canada Code is OS

I've been thinking about getting that one. I already have two Chevelle books & some old Chiltons & Haynes manuals from the 70's. Just didn't know how well laid out that book was. Now I know what to ask for a Christmas present though.