Rear Axle
Driveshaft ]                                             

Home
Background
Body
Engine
Fasteners
For Sale
Holley
Interior
Links
Muncie
My Z28s
Options
Photo Album
Rear Axle
Restoration
Sales Info
Stickers/Road Test
Trim Tag
Wiring Diagrams

Last Updated:  Dec 20, 2021 added fill plug and plastic red label

Click On thumbnails for larger view

 

3.73 Posi

 

 

Inside & outside diff cover

Differential ID Codes

doc_diff_id_codes.jpg (21903 bytes)

Plant Codes:

G = Detroit Gear & Axle

B = Buffalo NY

W = Warren MI

 

Positraction Codes:

D = Dana posi diff

E = Eaton posi diff

W = Warren Motive

 

Decode - COZO522G

                        E
COZ = 3.73 Camaro Posi axle
05 = Month: May

22 = Day: 22nd day
G = Assembly Plant: Detroit Gear & Axle
E = Posi Source: Eaton

 

    Posi or Non Posi

 

Gear Ratio Code
2.56:1 COA
2.56:1 COB
2.73:1 COC
Posi 2.73:1 COD
3.08:1 COE
Posi 3.08:1 COF
3.36:1 COG
Posi 3.36:1 COH
Heavy Duty 3.08:1 COI
Posi Heavy Duty 3.08:1 COJ
Heavy Duty 3.36:1 COK
Posi Heavy Duty 3.36:1 COL
2.56:1 COM
Posi 2.56:1 CON
4.10:1 COO
2.73:1 COP
Posi 2.73:1 COR
3.07:1 COS
Posi 3.07:1 COT
3.31:1 COU
Posi 3.31:1 COV
3.55:1 COW
Posi 3.55:1 COX
3.73:1 COY
Posi 3.73:1 COZ
3.07:1 CRA
3.31:1 CRB
3.55:1 CRC
3.73:1 CRD
4.10:1 CRE
2.56:1 CRF
Posi 2.56:1 CRU
Heavy Duty 3.08:1 CRH
Posi Heavy Duty 3.08:1 CRI
2.73:1 CRX
Posi 2.73:1 CRY

 

 

 

                                Positraction Casting Numbers

 

Axle                Casting Number Series    Gearing
12-bolt Passenger ED 32088 2 2.73:1 and down
  30140PM1 3 3.08:1 to 3.73:1
  EDB 30174 4 3.90:1 and up
Corvette ED 32297 PW 3 3 2.73:1 to 3.70:1
  EDB 32298 4 3.90:1 and up
8.5 corporate 410408N 3 2.73:1 and up
  410409N 2 2.56:1 and down
8.2 10-bolt ED 21118 2 2.73:1 and down
  EDB 30116 3 3.08:1 and up

 

Differential Stamped Numbers

 

Rear Axle Gear Ratios

 

 

Date code is 3 70 for March 1970

The gear tooth ratio of the ring and pinion for example

11 41 as shown is stamped on the pinion head or stem and

also on the ring gear. Therefore you can calculate the axle ratio.

 

Ring gear tooth count = 4 1

Pinion tooth count = 11

 

41 11 = 3.73

 

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

 

 

Rear Ends

 

  1970 1970 1971-75
  10-Bolt 12=Bolt 10-Bolt
Bolt Diameter (in.) 3/8 3/8 7/16
Ring Gear Diameter (in.) 8.20 8.875 8.50
Pinion Diameter 1.438 1.625 1.625
Axle Splines 28 30 28
Overall Dimensions:      
Axle tube flange to axle tube flange 55 1/4 55 1/4 55 1/4
Between centerlines of spring seats 45 3/8 45 3/8 45 3/8
Axle shaft length 30 5/32 30 5/32 30 5/32

 

Remember if you have a posi unit to add 2 bottles of limited slip lubricant.