Rear Axle Identification

Blake442 · Apr 25, 2010

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

malibuSSwagon · May 31, 2010

So how durable is the 7.625 rear end compared to the 7.5? I have a one wheel peel 7.625 out of an 87 SS for the wagon

johnny79 · Jun 9, 2010

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)

ilduce · Jun 30, 2010

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 · Jun 30, 2010

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.

zums · Jul 5, 2010

my axel tube 2TJ anyone know what this stands for

eocoolj · Jul 31, 2010

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...

kuruption109 · Aug 30, 2010

good info im goin to see what my car is equipped with..

442Jayp · Jan 17, 2011

kuruption109 said:
good info im goin to see what my car is equipped with..

i am also doing the same thing today

MR442 · Jan 18, 2011

Thanks for the write up 3.73's here

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Rear Axle Identification

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