70-81 camaro rear axle decoding

Second Generation Camaro
Rear Axle Information


Rear Axle Information
The 1970 rear end differs from the 1971-1981 rear end. In 1970 the rear end was built in both 10 and 12 bolt versions. In 1971, GM instituted a standardized "corporate" rear axle. This rear end was available in a 10 bolt version only. The 1970 12 bolt version will bolt into any second generation Camaro and quite often is done so in high power applications.

Description
Three piece housing includes integral cast iron differential carrier and housing with pressed in and welded steel tubes.
Semi-floating forged and heat-treated axle shafts. Wheel drive flange is forged integral with the axle. Axles are the same length for both sides.
Differential carrier contains hypoid overhung pinion and ring gear. Drive pinion supported by two taper roller bearings.
Rear Suspension - Salisbury rear axle with multiple leaf springs.
Staggered shocks, right side shock is located in front of axle tube and the left shock is located behind the axle tube. This controls wheel hop.
Leaf Springs - All leaf springs were 5-leaf design, 56" long, 2.5" wide.
See yearly info for specific specifications.

Physical Dimensions
1970 10 bolt 1970 12 bolt Corporate
Bolt Diameter 3/8" 3/8" 7/16LH
Ring Gear Dia 8.20" 8.875" 8.50"
Pinion Dia. 1.438" 1.625" 1.625"
Axle Splines 28 30 28


The following dimensions are consistant across all 3 style rear ends.
Axle tube flange to axle tube flange: 55.25"
Between centerlines of spring seats: 45 3/8"
Axle shaft length: 30 5/32"

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 (on 2nd generation) and forward facing drivers side axle tube (on 3rd gen) camaros. It'll usually be about 3 inches away from the carrier housing (center section of rear end housing).

1971 Z28 rear axle code

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.

1970 Axle code example: COZ 01 01 G E
(COZ = Ratio, 01 = Month, 01 = Day of month, G = Plant, E = positraction source)

1971+ 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
Plant Code Plant Code
Buick B Warren, MI W
Buffalo C Oldsmobile O
Cadillac D Pontiac P
Detriot Gear & Axle G Pontiac/Canada M
GM of Canada K

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

Positraction Source/Code:
- = No positraction G = Chevrolet G&A Positraction Carrier
D = Dana Positraction Differential O = Oldsmobile Positraction Carrier
E = Eaton Positraction Differential 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, 2.73:1 & down = 2.41, 2.56, etc... which is actually a HIGHER gear ratio.

8.2" 10 bolt 8.5" "Corporate" 12 bolt
Casting # Series Gearing
ED32118 2 2.73:1 & down
EDB30116 3 3.08:1 & up

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

Casting # Series Gearing
ED32088 2 2.73:1 & down
30140PM1 3 3.08:1 to 3.73:1
EDB30174 4 3.90:1 & up