I'm hoping to get some knowledgeable info on this subject from someone who has done this before. I want to change ratios from stock to 3.73:1. Here are the questions:
1) Heard some 3rd gens have an Austrailian rear axle assembly with very expensive R&P. Is this the case here? If not, what is the common nomenclature for the rear end? 10 bolt? 7.625" Ring gear? What exactly does this car have from the factory?
2) Can the R&P be changed in chassis or does the axle assembly have to be removed? If so, why?
3)Does a pinion depth gage have to be used or do you feel the pinion shim is usually dictated by the axle housing, thereby allowing for the same shim to be used.
4) What controls the speedometer. Is it gear driven off the trans or does this vehicle use a tooth wheel on the ring gear.

I plan on doing this work myself, so any suggestions are appreciated.
Regards, FJK

 

If you have the BW 9-bolt, you are SOL about the 3.73. If your cover is kinda squarish w/ 10 bolts, then its a 10 bolt. If not, then you probably have the BW 9-bolt.

Everything else you inquire can be found here: 10 bolt

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'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE

 

Yes, your 88 GTA (350 L98 with automatic, right?) should have the australian 9-bolt rear with 3.27 gears. It might have 2.77's but I doubt it. If you have the 3.27's a couple manufacturers have 3.70 ratio gears for it. Or search this forum for more info.

You can change the ring&pinion while the axle is in the car.

#3 I dont know, but I'd use a pinion depth gauge to be sure.

The speedometer is gear driven off the trans, to an electromagnetic pickup which goes to the computer, on your GTA.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
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Ummmmm....not true

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88 427 Camaro
12.18 @ 113mph 1.75 60ft
Currently installing 3.73's into my 9 bolt (YES,it is a 9 bolt & YES they are 3.73's, not 3.70. 4.11's to follow soon )
www.koolmeister.com

 

Hmmm, didn't know that. At least me being wrong is good news!

------------------
FREE CARFAX Record Check

If you live in Southeastern US, check us out!
South East Thirdgen

GM Master Tech
ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE

 

I've been working on this for a while now. The 3.73 has 11 pinion teeth vs 10 on the 3.70, which makes it stronger. I should have (ie parts in hand) solid info next week.

Miles

------------------
88 427 Camaro
12.18 @ 113mph 1.75 60ft
Currently installing 3.73's into my 9 bolt (YES,it is a 9 bolt & YES they are 3.73's, not 3.70. 4.11's to follow soon )
www.koolmeister.com

 

88 427
What Brand R&P did you buy & where did you get it from?

Everyone, thank you for the information. Sounds like if this car does have a 9 bolt rear end, not many people have done gear changes on them.
Regards, FJK