1971 Chevelle Rear Axle Identification
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The rear axle identification code consists of at least a two letter prefix indicating the gear ratio, a letter for the manufacturer's identity, and three digits indicating the day of the year from January 1 and other codes as necessary. The identification code should be stamped on the bottom or font of right axle tube either adjacent to the carrier housing or about 8" - 10" inboard from the backing plates. The particular engine RPO code is listed in parentheses as found on buildsheets.
Example: RUC064(1 or 2) decodes to RU ~ 3.31:1, C ~ Buffalo, 064 ~ day of year starting with January 1 (the 64th day being March 5), 1 or 2 ~ shift (if present). See bottom of page for photo examples.
Casting Numbers:
12-Bolt Casting #3969278
10-Bolt Casting #3969277
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.
Gear Ratio - First & second characters| Prefix | Axle Ratio |
| CF | 3.31:1 ~ 12-bolt Positraction |
| CH | 2.73:1 ~ 12-bolt Positraction (L48/350-4, LS3/330-4)* |
| CW | 3.31:1 ~ 12-bolt (L48/350-4)* |
| GA | 2.56:1 ~ 10-bolt (L65/350-2)* |
| GB | 2.56:1 ~ Positraction |
| GD | 2.73:1 ~ Positraction |
| GF | 3.08:1 ~ 10-bolt |
| GG | 3.36:1 ~ 10-bolt (base L6)* |
| GH | 2.73:1 ~ 10-bolt (L14/307)* |
| GI | 3.36:1 ~ Positraction |
| GN | 3.08:1 ~ 10-bolt (L14/307)* |
| KD | 2.73:1 ~ 12-bolt (L48/350-4)* |
| RU | 3.31:1 ~ 12-bolt (LS5/454)* |
| RV | 3.31:1 ~ 12-bolt Positraction (LS5/454)* |
| RW | 4.10:1 ~ 12-bolt Positraction(LS5/454)* |
|
|
|
| Code | Assembly Plant |
| C | Buffalo, N.Y. |
| G | Detroit Gear & Axle |
| K | McKinnon Industries (GM of Canada) |
| W | Warren, MI. |
Assembly Day - Day of the year, 000...365
Shift - 1 or 2 (or Day / Night) if applicable
KD ~ 2.73:1, K ~ McKinnon Industries, January 11th (11th day of year)
GN ~ 3.08:1, K ~ McKinnon Industries, February 21st (53rd day of year)
CH ~ Positraction 2.73:1, Buffalo, March 5 (64th day of year), 2nd shift,
Eaton Positraction
* Engine RPO code and size following the rear axle ratio are taken from buildsheets or warranty Protect-O-Plate cards and may not reflect the only engine the rear axle codes came with. Where there are no RPO/engine information following the rear axle code only means I do not have buildsheets to verify them.
