REAR AXLE IDENTIFICATION

The rear axle identification code consists of a three letter prefix indicating the manufacturing plant and 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.

C = Buffalo, N.Y. manufacturing location
GC = 2.73
223 = August 10

Rear Axle Assembly Plant - First character
Code Assembly Plant
C Buffalo, N.Y.
G Detroit Gear & Axle
K McKinnon Industries (GM of Canada)
W Warren, MI.

Prefix Axle Ratio
GD 2.73 ~ Positraction
GF 3.08
CH 2.73 ~ Positraction
GA 2.56
*GC 2.73
GG 3.36
GB 2.56 ~ Positraction
GI 3.36 ~ Positraction
KD 2.73
CW 3.31
CF 3.31 ~ Positraction
RU 3.31
RV 3.31 ~ Positraction
RW 4.10
GH 2.73
GN 3.08

Assembly Date - 3-digit number is Julian date.  The day 013 is the 13th day of 1971, or January 13, 1971.  Any number between approximately 200 (mid-July) and 365 (end of December) are days from January 1, 1970. One must look at the other component dates to be sure.