Last Updated: Dec 20, 2021 added fill plug and plastic red label
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3.73 Posi
Inside & outside diff cover
Differential ID Codes
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.
