89 GTA Dave

I have purchased a TPI transmission and am getting ready to put it in, but do not know what gear to use in the rear, I have a 2000 stall speed convertor and light mods so far I plan on eventually getting heads and a bigger cam should I go 3.42 or 3.73 it currently has 3.27 in the bw 9 and I plan on putting in the gm 10 bolt any suggestions anyone?

Dan87IROC-Z

Both those rear ends will work well. It depends on what type driving you do and how much you care about your MPG. If you do a lot of high way driving, I'd go with the 3.42s. My friend has 3.45s in his 88 IROC and it seems perfect for pretty much everything he does.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: LT4 Hot Cam, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Gutted Catalytic Converter, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, Fully Ported TPI Plenum and Base, All Free Mods, Falken ZIEX Z-Rated Tires.

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

Superman

I agree with Dan,the 3.42 is a great all around gear choose. It gets out of the hole ok,and still has good top end speed all without working the engine very hard.

IrocStan

3.42's dropped my quarter by a solid .4-.5 over the 2.73. I went from 95mph to 101. That is on worn out radials. I have a brand new 3.73 sitting in my garage that I want to swap in sometime to see if there is much improvement. I am guessing that I won't see much, if any, improvement with the radials, but with the 27x10's it will definitely help.

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87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Goal: 12.999

FastBroker

If you can hook-up your tires and your engine breathes fire at the higher rpm's, bigger gears ALWAYS help!