STAYBG

well i have a pretty good hook up on gears and i was gonna get a 3:42 and a couple of guys talked me into getting a 3:73 cause i figured im getting a couple of other things done besides my mods that i have now.i have a pretty decent intake setup right now that pulls really hard.i plan on getting 64cc heads,high flow base manifold,and runners.so ill have plenty of breathing room.but i wanna know your guys input.my current mods are at the bottom.

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1987 IROC-Z28
355 TPI
58MM HOLLEY TB
HOME PORTED PLENUM
LT1 INJECTORS
HEDMAN HEADERS
CRANE AFPR
MSD WIRES
JET FAN SWITCH.


STILL TO COME,
3:73 POSI DISK REAR
4' COWL HOOD
4TH GEN INTERIOR
ALL AROUND SUSPENSION KIT

IROC Z 350

Do you race? By all means go 3.73. If you plan on ANY long trips in the car go with 3.42. They still perform well and are a good all around gear. Highway with 3.73's sucks but the performance is AWESOME!

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*1985 Camaro IROC-Z28 H.O. 350 A4 3.73 TPI Accel 58mm runners 24# injectors hughes 700R-4 3000 stall BFG DR's and..
*2000 Camaro Z-28 A4 3.23 MTI lid K&N Flomaster !EGR Ram Air Cutout

IZ28

With TPI I would go with 3.42's.

91Bird305

The difference between 3:42's and 3:73's are almost the same. I have had both. If you plan on doing a lot of highway driving I would go with something in the low 3's. Like 3:08's would be best but really my top end was not crippled by my gears, I can still hit over 100mph easy and nothing to worry. Do u have an auto or manual? If you have a manual, go with the 3:42's, if you have an auto, go with 3:73's.

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1991 Firebird 305
Eric Natzke
"It ain't Stock"
http://members.aol.com/j007golden/91firebird.html

NJ SPEEDER

really teh difference in 3.73 and 3.42's at highway speeds is very small. only about 200rpm at 65 mph. if you go faster the rpm difference will be more, but not much. there will be little if any difference in highway mileage between the two.

later
tim

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NJ SPEEDER
91 Camaro RS
305TBI/700R4
12's Coming Soon
2nd Annual East Coast F-Body Nationals
July 20,2002
www.geocities.com/njspeeder
My MAFB.ORG Home Page
http://www.mycar.net/mafb/registry/detail.cfm?id=299

IROC Z 350

First of all, I've had both 3.42 and 3.73 too and I disagree. I drove my IROC from Phoenix to Vegas with 3.42's. Not too bad. After the 3.73 switch there was no way in hell I would make that trip...stopping at every available gas station in sight. Running over 3000 RPM at 75mph. Not good.

Second: Sounds like he already has 3.08's or 3.23's and is looking for more snappy performance. You can't go wrong with 3.42's. Steet, strip, highway...all good. 3.73 is simply street/strip performance for a car that for the most part...is staying in town. JMHO.



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*1985 Camaro IROC-Z28 H.O. 350 A4 3.73 TPI Accel 58mm runners 24# injectors hughes 700R-4 3000 stall BFG DR's and..
*2000 Camaro Z-28 A4 3.23 MTI lid K&N Flomaster !EGR Ram Air Cutout

RedIrocZ-28

IROC Z 350, why were you at 3000 RPM and only doing 75mph? I'll tell ya right now you didn't have 3.73's in there. I have 3.73's and I am doing 75 mph at 2500 RPM and closer to 90 at 3000 RPM

For STAYBG- If you plan on having an intake setup that will be able to flow and have good numbers up to almost 5500-6000 RPM then I would say 3.73's are for you.

Blk91Z28

I have 3.73s in my 91 z28 with a 700r4 and im over 3000 rpms at 75 mph.I had 3.42s in my car before the 3.73s and the car was faster w/3.42s.

RedIrocZ-28

Uh oh... does anyone know how to check the gear ratio by spinning the tires and driveshaft?

I wonder if the insurance company screwed me! I paid for them to put 3.73's and a new posi carrier in there.

Edit: I just went and played with a gear calculator over at thirdgen.org and can't figure out how a car equipped with 3.73's and a 700R4 with the factory 245/50/R16 tires could be over 3000 RPM at 75mph.

Try it yourself. The factory tires have an approximate radius of 13" and the 3rd gear ratio is 1.0:1 while overdrive is .7:1

Anyone agree/disagree with me?

[This message has been edited by RedIrocZ-28 (edited June 24, 2002).]

mikesanto70

Dude, you are totally wrong, first of all a factory tire, lets say IROC-Z is a 245/50/16 that has a radius of 25.7 inches, and it's 4th gear in a 700R4 that has a ratio of 1:1, This information I gave you is 100% accurate, so do your calculations off of those "REAL" numbers. !!!!

Uh oh... does anyone know how to check the gear ratio by spinning the tires and driveshaft?

I wonder if the insurance company screwed me! I paid for them to put 3.73's and a new posi carrier in there.

Edit: I just went and played with a gear calculator over at thirdgen.org and can't figure out how a car equipped with 3.73's and a 700R4 with the factory 245/50/R16 tires could be over 3000 RPM at 75mph.

Try it yourself. The factory tires have an approximate radius of 13" and the 3rd gear ratio is 1.0:1 while overdrive is .7:1

Anyone agree/disagree with me?

[This message has been edited by RedIrocZ-28 (edited June 24, 2002).][/QUOTE]

SupplySgt.

Actually, stock tire height is approx. 25.6 inches. My IROC with 225/55/16s have a tire height of 25.7 and it's slightly higher than the stock tires. And if the 700R4 had a 4th gear ratio of 1:1, then it wouldn't be an overdrive transmission now would it? Going by that logic a 4 speed muncie (which has a 4th gear ratio of 1:1) would actually have 3 speeds with overdrive. which it does not. 4th gear (OD) in a 700R4 does have a .70 gear ratio.

ws6transam

You resurrected a seven year-old dead thread just to start an argument? Better re-check your facts. The 4th gear of a 700R4 is 0.7:1 and 3.73 gears will yield a 2600 RPM cruising speed at 70 MPH on stock diameter tires. Perfectly fine ratio for third-gens. My car has been equipped with 3.73's for twenty-five years. This wasn't a good way to start your first post & introduction to CamaroZ28.com ... Try again.

the_chadster

I had a 84 TA with 400 SB (prob 375 HP), 700 R4 with the lock-up still hooked up, and I put in 3:73 gears and thought they were perfect. I would even consider 3:90. I wrecked it in the end of 99, so going from long term memory, I think I was at about 2500 at 70. If your power range is still low end because of TPI, the 3:42 may be better for you, just a matter of personal preference. I loved the 3:73 on the highway because it put me right at the bottom of my power range, and would smoke anybody who wanted to play at 70. Just sucked when the tranny wouldn't hold 4th when I floored it.

BTW - radius is the distance from the center to the edge, diameter is all the way across, circumference is all the way around, seems there was some confusion about that.

palric

I've had 2.73s, 3.08s, 3.23s,3.42s and 3.73s

these days no one is using a 20 year old 3rd gen for a daily driver so for 99% of us its pretty much a "what cam?" choice.

I have 3.23s but after swapping to a T5 (from auto) am looking at 3.73s (they are way more fun for street and strip) because I am going to put .540 list cam in.

I would probably go with the 3.42s if not changing the cam.

SupplySgt.

Don't blame you on the 3.73s. I disagree on the nobody uses a 3rd gen as a daily driver. My IROC is my daily driver. I know several people with 3rd gens who use them as daily drivers.