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 build sheets.

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 (L48/350-4 & LS3/402)*
CH 2.73:1 ~ 12-bolt Positraction (L48/350-4 & LS3/402)*
CW 3.31:1 ~ 12-bolt (L48/350-4 & LS3/402)*
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 & L65/350-2)*
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 & LS3/402)*
RU 3.31:1 ~ 12-bolt (LS5/454)*
RV 3.31:1 ~ 12-bolt Positraction (LS5/454)*
RW 4.10:1 ~ 12-bolt Positraction **

* Engine RPO code and size following the rear axle ratio are taken from build sheets 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 build sheets to verify them.

** To date, no build sheet or other documentation has shown up with a Positraction 4.10:1 rear axle ratio. GM documentation for 1971 only shows a 4.10:1 available with the LS6 which was never released in the Chevelle for public sale. Additionally the RPO option ZQ9 for a performance axle only shows 302 of these options sold. The Positraction 4.10:1 and the 3.08:1 axle ratio are shown as available under ZQ9. With such a low sales of ZQ9 in 1971, one can conclude the 302 sales must be for the 3.08:1 ratio available as an option with the base 307 V8 that came standard with a 2.73:1 axle ratio.

Rear Axle Assembly Plant - Third character

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

Examples

CHEVELLESTUFF  All Rights Reserved
RUC ~ 3.31:1, Buffalo, NY, January 9th (9th day of year), 2nd shift

CHEVELLESTUFF  All Rights Reserved
KD ~ 2.73:1, K ~ McKinnon Industries, January 11th (11th day of year)

CHEVELLESTUFF  All Rights Reserved
GN ~ 3.08:1, K ~ McKinnon Industries, February 21, 1971 (53rd day of year)

CHEVELLESTUFF  All Rights Reserved
CHC ~ Positraction 2.73:1, Buffalo, March 5, 1971 (64th day of year), 2nd shift, Eaton Positraction

CHEVELLESTUFF  All Rights Reserved
CFC ~ Positraction 3.31:1, Buffalo, March 10, 1971 (69th day of year), 2nd shift, Eaton Positraction

CHEVELLESTUFF  All Rights Reserved
RVC ~ Positraction 3.31:1, Buffalo, August 3, 1970 (215th day of year), "B" is unknown

CHEVELLESTUFF  All Rights Reserved
KDC ~ 2.73:1, Buffalo, August 17, 1970 (229th day of year), "A" is unknown

Casting Date Examples

CHEVELLESTUFF  All Rights Reserved
Casting date example K 9 1 for November 9, 1971

Casting Number Examples

CHEVELLESTUFF  All Rights Reserved

CHEVELLESTUFF  All Rights Reserved
CHEVELLESTUFF  All Rights Reserved
CHEVELLESTUFF  All Rights Reserved
1970-1972 ~ Variations of casting number 3969278