Mikos_89

A mechanic told my uncle that he couldn't put 3.23 gears into his '91 Z28 because the differential is to small. The mechanic said the largest gears that could fit in the housing would be 3.08 gears not 3.23.

The car is a '91 Z28 with a 305 TPI/700R4 with RPO (GU2) 2.73 rear gears.

Why on earth would GM make a slighty different corporate 10-bolt rear-axle for 2.73s-3.08s verses 3.23s and up?

I know GM has a done some pretty weird things in the past, but this tops the list.

I do remember reading here of a few people upgrading their GM 10-bolts to 3.23s and up from their 2.73s. So I guess you can use the same rear-axle housing assembly. Right?

Is this mechanic on drugs or what?

Thanks.
-Mike



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'89 GTA: blk on blk with 5.7 liter, T-tops, leather, N10 dual exh with 76,500 original miles. 100% stock including the ZR50 Goodyear "gatorback" tires.

SoCo80p

iTrader: (5)

the differential itself can take just about any gears, its the CARRIER that will only take certain gears, generally a 2-series (what you have) will like he says only take to a 3.08, you need to swap carriers to make it work, eather a used one that had 3.23 or higher numerical gears, or a aftermarket unit.

F-BIRD'88

He might be on drugs but....

Try getting a ring gear spacer. $50.
It adapts a 3 series gear to a 2 series
posi. Should include specal ring gear bolts too. (longer). Have a pro install it for ya.
The setup of a rearend ring and pinion set
must be done correctly or it will self destruct in a few miles. Not worth skimping here.

[This message has been edited by F-BIRD'88 (edited November 03, 2001).]

E-Z Rollin

Go to SLP's web site,get the zexel unit[new take out $99]it will take 3.23 and numericaly higheer gears.

JamesC

iTrader: (5)

TempesT68,

So my 3.23 carrier (85 IROC) will accept 3.42 or 3.73s? If so, what cars can I expect to find the latter gears in? What are the RPOs?

JamesC

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F-BIRD'88

Look for 3.42's in 2.8 litre v6 EFI/auto FireBirds
find 3.73 in early 305's with a 5 speed
or S10's.....

82camaro

New gears can be had in both 3 series and 2 series. For example 2 series 3.73's from richmond--no spacer needed, they are built for the 2 series carrier. That's what I have in my 82.

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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

SC88

Good luck trying to find a ring gear spacer for a 7.5 rear end. I tried and the best thing someone said is that the 7.5 is the weakest GM rear, why would you want to make it weaker? Look in the Summit catalog very carefully, you will find a set of 3.73 gears for a 2 series carrier and a set of 3.73's for a 3 series. The difference is about 1/4". Do not ring space. Spend the $195 for the right thing.

SC88

Good luck trying to find a ring gear spacer for a 7.5 rear end. I tried and the best thing someone said is that the 7.5 is the weakest GM rear, why would you want to make it weaker? Look in the Summit catalog very carefully, you will find a set of 3.73 gears for a 2 series carrier and a set of 3.73's for a 3 series. The difference is about 1/4". Do not ring space. Spend the $195 for the right thing.

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1988 Camaro Sport Coupe: Orignally: 305 TBI 700r4
Now: 1974 355CI, 2bolt, Badger Flat Head Pistons w/ valve relief, Melling high performance street cam, GM Cast Vortec Heads, Edelbrock RPM Air Gap Intake, Edelbrock 600cfm w/ electric choke, GM HEI w/ vacuum advance, Weiand Low Profile Air Cleaner, Mallory 5 port Fuel Pressure Regulator, Mr. Gasket Throttle Cable Bracket, Corvette Shift Servo, 16" IROC Wheels, Every thing else is STOCK
Soon: 3.73 or 3.42, Gears, Hoosier Q/T