Is this a big project or is it easy? The rear will be out of the car, it has 140,000 on it. If the gears are good should I even replace the posi unit. I'll be going from 2.77 to 3.23 that will be the hole rear every thing. What else should I do the rear before I put it on?

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87 Z28 305 TPI, Auto, 2.73, Gutted air boxes, K & N fillters, Dyno Max 3" cat back, Accel 8.8 mm spirals, Accel cap and rotor, Accel coil, rapid fires, and 160 Stat.
Best 15.414 @ 87.47

 

Check the posi (if its on your car right now). Jack the rear of the car up and get your mailman (or mom) to spin one tire. Grab the other rear tire. If its difficult to keep still, then your posi is still good.

If it's easy you'll need a new one.

Replacing the posi isnt hard.

However, you'll need your gears set up professionally unless you are knowledgable on the subject. Go to someone who knows their stuff. Expect to pay around $200 for the labor.

You'll need an installation kit. Look in Summit or Jegs. They'll run you around $100. Depending on the condition of your axle bearings..you could need those too....

One more thing, you may want to re-think what gear your going to. IMO I'd go with 3:73s for your setup.
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92 Formula
305 TPI 5speed
1LE package
Mods: SLP headers,SLP catback,SLP air foil,ported plenum,K&N, Crane AFPR (47psi),MSD6AL, MSD wires, AC DELCO cap/rotor/plugs, Bosch O2sensor, 3:73s,JET fan switch, Macewen white face gauges, Intellitronix Digital Gauges

[This message has been edited by theformula (edited December 10, 2000).]

[This message has been edited by theformula (edited December 10, 2000).]

 

I always read here on th e board that with an auto you should go with 3.42. Also I've read there is a real big diff in 3.42 and 3.23, is my thinking right here?

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87 Z28 305 TPI, Auto, 2.73, Gutted air boxes, K & N fillters, Dyno Max 3" cat back, Accel 8.8 mm spirals, Accel cap and rotor, Accel coil, rapid fires, and 160 Stat.
Best 15.414 @ 87.47

 

Anyone

 

if your posi is good don't replace it. for other up grades weld the axle tubes to the center section, use a girddle, mobil 1 gear lube, gm posi additive.

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ICON Motorsports
1st & 3rd

 

I converted from 3.42's to 3.73's in my 88 GTA 5.7L Auto. I notice a big difference. My 60' times droped a tenth of a second (1.9-1.8) and my quarter mile time dropped 2 tenths (14.6-14.4)on the gears alone. My MPH remained the same at the traps. Expect 1st gear to be a lot shorter under light throttle.

 

New87, who ever told you that had their head in their a$$.

I know guys here in Delaware running 4:10s in 90 IROCs and have seen performance gains. You'll lose a little top end though.

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92 Formula
305 TPI 5speed
1LE package
Mods: SLP headers,SLP catback,SLP air foil,ported plenum,K&N, Crane AFPR (47psi),MSD6AL, MSD wires, AC DELCO cap/rotor/plugs, Bosch O2sensor, 3:73s,JET fan switch, Macewen white face gauges, Intellitronix Digital Gauges

[This message has been edited by theformula (edited December 11, 2000).]