Rear Axle Identification

Blake442

Geezer
Apr 24, 2007
6,852
113
Minneapolis
Here's a listing of the performance oriented rear axles as offered from the factory in various G-body vehicles.

'83-'84 SS's had 7.5's with 3.42's and TH-350's.
'85-'87 SS's had 7.625's with 3.73's and 200-4R's.

'83 H/O's had 7.5's with 3.73's.
'84 H/O's had 8.5's with 3.73's.
'85-'87 442's had 8.5's with 3.73's. All had 200-4R's.

'84-'87 Turbo Buick's had 8.5's with 3.42's. All had 200-4R's.

Here are some gear ratio RPO codes for looking in other vehicles for specific gear sets...

G72-2.14 ratio
GH2-2.29 ratio
GU1-2.41 ratio
GM8-2.56 ratio
GU2-2.73 ratio
GU4-3.08 ratio
GU5-3.23 ratio
GT4-3.73 ratio

G80-limited slip differential

G87-8.5in 10 bolt axle
G89-7.5in 10 bolt axle

GM10-Bolt-75.jpg

GM10-Bolt-85.jpg
 
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johnny79

Greasemonkey
Nov 12, 2009
192
18
DC
Code:
RPO           |--------Axle Code--------|
Ring Gear   Code   Ratio   Conventional   Limited Slip
-------------------------------------------------------
  7.5       G72    2.14       2AK            2BK   (aluminum brake drums)
  7.5       GH2    2.29       2AH            2BH
  7.5       GU1    2.41     2AJ,2AZ        2BJ,2BZ
  7.5       GM8    2.56       2AA            2BA
  7.5       GU2    2.73     2AB,2AX        2BB,2BX
  7.5       GU4    3.08     2AC,2AV        2BC,2BV
  7.5       GU5    3.23       2AD            2BD
  7.625     GT4    3.73       2TF            2TH   (Monte Carlo SS)
  8.5       GU6    3.42       3TP            3TJ   (T-Type, GN Std.)
  8.5       GT4    3.73     3TG,3TE        3TR,3TX (442, GN Opt.)

  8.5       GU2    2.73       8YB            8YP   (B-Body)
  8.5       GU4    3.08       8YD            8YR   (B-Body)
  8.5       GU5    3.23       8YE            8YS   (B-Body)
 
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ilduce

Apprentice
Jun 6, 2010
58
0
johnny79 said:
Code:
RPO           |--------Axle Code--------|
Ring Gear   Code   Ratio   Conventional   Limited Slip
-------------------------------------------------------
  7.5       G72    2.14       2AK            2BK   (aluminum brake drums)
  7.5       GH2    2.29       2AH            2BH
  7.5       GU1    2.41     2AJ,2AZ        2BJ,2BZ
  7.5       GM8    2.56       2AA            2BA
  7.5       GU2    2.73     2AB,2AX        2BB,2BX
  7.5       GU4    3.08     2AC,2AV        2BC,2BV
  7.5       GU5    3.23       2AD            2BD
  7.625     GT4    3.73       2TF            2TH   (Monte Carlo SS)
  8.5       GU6    3.42       3TP            3TJ   (T-Type, GN Std.)
  8.5       GT4    3.73     3TG,3TE        3TR,3TX (442, GN Opt.)

  8.5       GU2    2.73       8YB            8YP   (B-Body)
  8.5       GU4    3.08       8YD            8YR   (B-Body)
  8.5       GU5    3.23       8YE            8YS   (B-Body)


So for GUI (2.41 gears in a 7.5 housing), is limited slip the normal setup or do I have positraction? I don't have 2BJ or 2BZ on my sticker. Looks like I have highways gears, though.
 

jrm81bu

Comic Book Super Hero
Jul 9, 2008
3,000
48
Antwerp, OH
Limited slip and posi-traction are the same thing. It was only an optio. The RPO code for it is G80. The other three digitcombos to the right on that chart(I think)are the codes you would find stamped on the axle tube, not your sticker.
 

eocoolj

Apprentice
May 27, 2010
83
0
Yikes didnt know they made a rear axle with an even smaller ratio than the 2.29 in my monte. Pair the 2.17 with an overdrive transmission, imagine what your theoretical top speed is...
 

442Jayp

Master Mechanic
Nov 11, 2010
279
0
kuruption109 said:
good info im goin to see what my car is equipped with..

i am also doing the same thing today
 

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