I'm thinkin bout getting some 3.73 positive traction gears for my 90 IROC. You can just replace the gears right?? I need to know a good place to buy these and prices. If you have 3.73 gears in your thirdgen let me know how you like it. And how much does it change your gas mileage??

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> 1990 IROC-Z (black)
> one of 3000 IROCs with a 305 made in 1990
> flowmaster exhaust
system with mufler bypass
> z-28 spoiler
> blue under car neon kit
> check out my site at: http://geocities.com/thickfacek/IROC-Z.html

> email me at thickfacek@nc.rr.com

 

my 350 slowed down with 3.73s. FYI I just weezed past 4600 rpm with my old heads.

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1991 Firebird
350 L98 (was a 305 TBI)
T-5 transmission
Edelbrock TES and cat back
Accel manifold
NOS
subframes
jegster torque arm
MSD Digital 6
AFPR
Lakewood lcas
Hurst linelock
SLP cam
relocated battery
cold air
Hypertech chip
centerforce clutch
poly bushings and mounts
AFR 190s
Harland sharp 1.5 rockers
a/f gauge
autopower rollbar

14.0 at 100 NA before heads


Juice and AFRs??......TBD

 

If your IROC has the 7.75" Borg Warner 9 bolt with a 2 series carrier, you would be better off looking for a used 10 or 12 bolt on ebay or at a salvage yard with 3.42s or 3.73s. If your car has the 3 series carrier (3.23+) then you can get a set of 3.70s or 3.45s from Strage gear. If you do have the 2 series carrier (3.08 down), a new carrier will be a fortune, so I'd go with the 10 or 12 bolt then.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base

 

with TPI you want to stick around 3.55 or numerically lower gears as the 3.73's will actually make you hit your rev limiter

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I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package , dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

 

went one tenth faster and 1 mph faster by switching from 3.73's to 3.23's (yeap, you red right). I think 3.23's to 3.42's are the best suited gears for TPI's, because of our operating band (1500 to 5000) and we have enought torque to get off the whole with 3.23's...plus the mpg went back up, and I love cruising at 80 on the interstate at like 2300 rpm....

 

There is no "rev limiter" on TPI thirdgens, bonehead !

 

Then explain why when in park, I mash the gas it just sits at 5700 rpm cutting out? My guess would be rev limiter.

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89 Iroc 350 TPI,
Forged pistions
Comp Cam .510 lift 230dur
Flowmaster exhaust
Aluminum Heads SOON!!!
MINI RAM SOON!!!!!
stock TPI for now 24# inj

 

Unless you have a custom (or home-burned) chip, then valve float is what's limiting your RPM. There is a rev-limiter in the stock TPI chips, but GM set it at ~10k rpm since they never used it. I and many others have re-set it to something more practical depending on one's engine combination and how high you're willing to rev your engine.

------------------
Greg Westphal
'87 IROC 305TPI/A4

 

if you put 3.73's instead of the stock numerically low gear (2.73) l think? would you need to upgrade tires? what kind of tires would you reccomend?

 

you can buy gears for both 2 & 3 series carriers, not much price differance between brands, if any.

2. i'm nearly positive it is valve-float, our cams are pathetic and the springs match them (which is good because there would have been a lot more blown small blocks in these cars) especially when holding it WOT in park in your driveway.

3. you dont NEED different tires but the extra gear will probably overwhelm them into a free spin from dead stop. AKA-burnouts
if you get into the habbit of performing "smokeshows" for your friends you WILL be buying new tires -monthly. if you drive normally they will be totaly fine.
to prevent wheelspin use stickier tires, but they're not recomended for normal street use- they're soft and wear really fast.

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89 Trans Am
jet black w/ silver flake
suncoast ram-air hood
ASAI aerowing
centerline trigons
SLP headers, flowmaster.
Viper 550esp w/ rem start
Grant GT, all Kenwood.
BMR adj.phr, lca's, lca brackets, sfc's, jamex springs, PSC front end

 

Bonehead? have you ever driven a car with TPI?



------------------
I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package , dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

 

Unless you change your cam to make power to 6500 rpm, then do not go any deeper then 3.42's. You do not have the engine for 3.73's.

 

Well I don't know about you guys but when my speed limiter kicks in at about 110MPH it is like hitting a brick wall!!! It scared the hell out of me the first time.....I knew it was there I just didn't expect it to be so abrupt. I gotta put a switch in I guess or burn a prom to take care of it.

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91 Z28 Camaro
305 TPI
Flowmaster 3" exhaust
700R4 with 2000 Stall and shift kit 3.42 rearend
One sweet sounding system

 

Tough call I think I have heard both arguments I talked to a guy with a 305 and 3:73 he said it was fast and fine. Also heard the arguement for 3:42 almost as good little bit better on gas milage. I will trying to decide which one to do myself. Tough decesion I think. 3:42n are a better overall gear I have heard but if you only drive around town and dont do much highway cruising then 3:73 will work. Both things were told too me by people with TPI powered cars.

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http://sites.netscape.net/bulldogfrazier/homepage
+
http://www.fracoinc.com/


Keep your ride shinning with pride

 

dude, trust me, you do not want 3.73's unless you make power up to about 6k. Your TPI isn't...just like mine...like I said before, I went 1 tenth faster and 1 mph faster going from 3.73 to 3.23 I have the time slips to back it up...I also have a friend that ran high 10's with 3.27, and his power band was 2000 to 5100 (dynoed) (he was turbocharged), and he also went 3 tenth faster and 4 mph faster going from 3.73 to 3.27 ... but if you have some $$ to throw away than go head and experiment with 3.73 then 3.42/23 ... I actually enjoy my car a hole lot better with 3.23's, it is like having an extra gear, I can dowshift to 2nd at 45mph and it puts me right at 3k, then I'm outta here...hehe, were the 3.73's it would put me at 4500, make noise and not go anywhere....