Hitman's Pontiac Trans Am Page | 1978 Pontiac Trans Am
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Rear End Codes
The axle code, which is a two-character code, is stamped on the front passenger side axle tube to the left of the carrier case. For example, axle code PX G70621 found on a 1977 Trans Am would be deciphered as; PX = Ring and Pinion Gear size 3.23(shown below), G = Manufacturer, Chevrolet Gear and Axle, 062 = Julian date which is the 62nd day of 1977 or March 1, 1977, 1= is the shift when built, in this case 1st shift.
1967
UN - 2.56 Rear Gear (Posi)
UP - 2.78 Rear Gear (Posi)
UR - 2.93 Rear Gear (Posi)
US - 3.08 Rear Gear (Posi)
UT - 3.23 Rear Gear (Posi)
UV - 3.36 Rear Gear (Posi)
UW - 3.55 Rear Gear (Posi)
UX - 3.90 Rear Gear (Posi)
UY - 4.33 Rear Gear (Posi)
1968
UN - 2.56 Rear Gear (Posi)
UP - 2.78 Rear Gear (Posi)
UR - 2.93 Rear Gear (Posi)
US - 3.08 Rear Gear (Posi)
UT - 3.23 Rear Gear (Posi)
UV - 3.36 Rear Gear (Posi)
UW - 3.55 Rear Gear (Posi)
UX - 3.90 Rear Gear (Posi)
UY - 4.33 Rear Gear (Posi)
1969
ZB - 2.56 Rear Gear (Posi)
ZC - 2.78 Rear Gear (Posi)
ZD - 2.93 Rear Gear (Posi)
ZE - 3.08 Rear Gear (Posi)
ZF - 3.23 Rear Gear (Posi)
ZG - 3.36 Rear Gear (Posi)
ZH - 3.55 Rear Gear (Posi)
ZK - 3.90 Rear Gear (Posi)
ZM - 4.33 Rear Gear (Posi)
1970
COF - 3.08 Rear Gear (Posi)
COL - 3.36 Rear Gear (Posi)
COT - 3.07 Rear Gear (Posi)
COV - 3.31 Rear Gear (Posi)
COX - 3.55 Rear Gear (Posi)
COZ - 3.73 Rear Gear (Posi)
CRY - 2.73 Rear Gear (Posi)
1971
CA - 2.73 Rear Gear (Posi)
CB - 4.10 Rear Gear (Posi)
CG - 3.73 Rear Gear (Posi)
CJ - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
1972
CA - 2.73 Rear Gear (Posi)
CG - 3.73 Rear Gear (Posi)
CJ - 3.42 Rear Gear (Posi)
CM - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
1973
CA - 2.73 Rear Gear (Posi)
CM - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
1974
CA - 2.73 Rear Gear (Posi)
CM - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
1975
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
1976
PS - 2.41 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
LD - 3.23 Rear Gear (Posi)
1977
PS - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
1978
PS - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PP - 3.23 Rear Gear (Posi)
1979
PS - 2.41 Rear Gear (Posi)
PV - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PR - 2.73 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PQ - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PP - 3.23 Rear Gear (Posi)
PO - 3.42 Rear Gear (Posi)
1980
PS - 2.41 Rear Gear (Posi)
PV - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PO - 3.08 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PQ - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PY - 3.42 Rear Gear (Posi)
PO - 3.42 Rear Gear (Posi)
1981
PS - 2.41 Rear Gear (Posi)
PV - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PQ - 3.08 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PY - 3.42 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
I had alot of help from various web sources and from the Catalog of Firebird ID Numbers 1967-93, the Parts and Illustration Catalog from Pontiac, and various other sources.
