1964 Chevelle
1965 Chevelle
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1970 Chevelle
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1972 Chevelle1964 Chevelle Rear Axle Date & Ratio Codes
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The rear axle identification code consists of a two letter prefix indicating the gear ratio - four digits indicating the assembly date as month/day - and a single letter suffix indicating the manufacturing location. The identification code should be stamped on the bottom or front left or right axle tube either adjacent to the carrier housing or about 8" - 10" inboard from the backing plates.
Example: YB 1025 decodes to YB - 3.36:1, 1025 - Month [Oct] and Day [25]
Casting Numbers:
10-Bolt Casting #3839390N
The casting numbers/letters on rear end housings may have either a prefix or suffix of "N" or "NF" and no reason has been found yet why they may have one or the other.
| Prefix | Axle Ratio |
| LA | 3.08:1 - 3 or 4-speed |
| LB | 3.36:1 - 3 or 4-speed |
| LG | 3.08:1 - Positraction |
| LH | 3.36:1 - Positraction |
| YA | 3.08:1 - 3 or 4-speed |
| YB | 3.36:1 - 3 or 4-speed |
| YG | 3.08:1 - Positraction |
| YH | 3.36:1 - Positraction |
| ZA | 3.08:1 - found with Powerglide transmission |
| ZB | 3.36:1 - |
| ZC | 3.08:1 - w/Metallic Brakes |
| ZD | 3.36:1 - w/Metallic Brakes |
| ZE | 3.08:1 - Positraction w/Metallic Brakes |
| ZF | 3.36:1 - Positraction w/Metallic Brakes |
| ZG | 3.08:1 - Positraction |
| ZH | 3.36:1 - Positraction |
| ZJ | 3.70:1 - w/Overdrive |
| ZK | 3.70:1 - Positraction |
| ZL | 3.70:1 - w/Metallic Brakes |
| ZM | 3.70:1 - Positraction w/Metallic Brakes |
| Assembly Month - 1st and 2nd numbers * | |||
| Number | Month | Number | Month |
| 01 | January | 02 | February |
| 03 | March | 04 | April |
| 05 | May | 06 | June |
| 07 | July | 08 | August |
| 09 | September | 10 | October |
| 11 | November | 12 | December |
| * It's not unusual for the month to be a single digit number | |||
Assembly Day - 3rd and 4th numbers
01...31
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Rear Axle Assembly Plant - 5th letter |
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| Code | Assembly Plant |
| B | Buffalo, New York |
| G | Chevrolet Gear & Axle, Detroit, Michigan |
| K | McKinnon Industries (GM of Canada) |
| W | Warren, Michigan |
ZA 1001 - 3.08:1 - October 1
ZA - 3.08:1 - June 23
Casting Date Examples
Casting date example of H 20 4 for August 20, 1964
Housing Casting
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