Thread: GM Rear Ends

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Whic GM cars and years had 2.73 rear ends? (GU2)

Well that's one of these "Have you stopped beating your wife?" questions. No easy answer. I know for sure every F bodied Third Generation GM car (1982–1992) had the GU2 as an option - depending on the engine transmission combination. It would be safe to say that there are a gazillion of these rear ends in bone yards across America.

From the rear end "bible of information that I may someday use":

Rear Axle Code example: GU2 O 030 1 EO
GU2 = Ratio - 2.73:1
O = Plant - Oldsmobile
030 = Day of year – January 30 (uses Julian Date, i.e., 1 = January 1st - 365 = December 31 [except Leap Year December 31st is 366])
1 = Shift – Day Shift
O = Positraction Code – Oldsmobile Positraction

Assembly Plant Codes:
B = Buick
C = Buffalo NY
D = Cadillac
G = Detroit Gear & Axle (OEM to General Motors)
K = General Motors of Canada -
W = Warren, MI
O = Oldsmobile
P = Pontiac
M –= Pontiac of Canada

Shift:
D or 1 = Day shift
N or 2 = Night shift

Positraction Code:
Blank = Non Positraction
D = Dana Positraction Differential
E = Eaton Positraction Differential
G = Chevrolet G&A Positraction Carrier
O = Oldsmobile Positraction Carrier
W = Warren/Warner Motive

Positraction Casting Numbers for 8.5" "Corporate"
Casting # Series - Gearing
410408N 3 - 2.73:1 and lower (larger numerically)
410409N 2 - 2.56:1 and higher (smaller numerically)

Rear Housing Casting Date
Example: E143
E = Month - May
10 = Day – 10th
3 = Last digit of year - 1993

Month: A = January, B = February and so forth incrementally through L = December

As to actual ratio codes - there's too many to list - Google them.

No guarantees here as I've seen some exceptions.Always need to take take the cover off and count teeth to be sure.

Best,
Glenn