My friend is parting out his IROC, and offered to sell me the 3.73 posi rear. Couple questions:

1. Can I put this in my car?
2. How hard is it? How would I go about doing it?
3. Would it be worth it?

Here's what my car will have when it's back on the road:

K&N drop in filters, side baffles removed from the air boxes
MSD 8mm heli-core wires
MSD6-A ignition
MSD GM blaster coil
Catco cat converter
Dynomax 2.5" cat back

How much will a 3.73 do for my performance?

 

you can ask TomP about this, he's done it.

as far as perfomance it should knock off 1-2 tenths from the 1/4, but it will give you a better feeling of low end torque. Also, your RPM's will be around 24-2500 in OD at 65mph , so you gas mileage may get a little worse.

 

Gas mileage is no concern. I just want to get to the next gas station faster.

 

What's your gas credit card number, I'll help ya charge it up!

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

I pay cash for my gas. Saves room on my credit card for Summit.

 

Mike, actually, if you search the transmission/drivetrain board, you'll find a ton of info I (and the other guys) have put up. The swap will be it's most simplest if the axle you're getting has drum brakes. That way you won't have to bother with the master cylinder or prop valve, or the differences in the front-to-rear brake line.

The one part I 100% recommend you replace is the body-to-axle brake hose. They're under $20, and re-using the old one is not the "safest" option.

While you've got the axle on the ground, you might want to do some maintainence on it. When I had my axle out, I did the following:

1. Replaced axleshaft bearings & seals (commonly misnamed as "rear wheel bearings/seals")
2. Rebuilt rear brakes (I had rear discs to rebuild, so it was much more work)
3. Painted axle with http://www.por15.com (used the $20 semi-gloss Super Starter Kit, it had just enough for the whole axle)

If your rear drum brakes are in better shape than the one on the IROC axle (don't ask me how you'd determine this...), you can swap the drums from your axle onto the IROC one. Here's a link on pulling/replacing the bearings: https://www.thirdgen.org/messgboard/...ML/000932.html

As to the swap itself? If both axles had drum brakes, it's easy. The Haynes 82-92 manual will tell you all the gory details, but in a nutshell: Oh, hey, nevermind. I did a search for "axle swap" and "TomP" in the suspension/chassis board, and found an old message of mine: https://www.thirdgen.org/messgboard/...ML/000718.html

Oh here's a fun tip to help with the physical removal of the old axle from under your car. Actually you could use it to roll the new axle into place, too. https://www.thirdgen.org/messgboard/...ML/001831.html I forgot about it when I did my axle... damn. That would've been a good photo

It'll definately be worth it. It's as straightforward (unbolt old, bolt-in new) of a swap as possible. Oh, also, two more things: Buy a torque wrench & use it! Last- Re-check all torques after driving the car for a day! I didn't do this, and lost my panhard-rod-to-body-brace bolt. My rear axle was swaying left-to-right, and the driveshaft was beating up my exhaust pipe. I'm so glad i was right outside my house when I lost the bolt!

By the way this will all be up on my "one of these days" web page, eventually...

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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!