Hello,

I currently have posi 2.73 gears. After reading someone else's post about a gear change to 3.42, I'm curious about it.

Apparently, everyone here runs with 3.73 and highly recommend them. Would it be a wise swap for my car or would it be too much?

I'm a tad bit confused about excatly what the gears do... do they simply help your engine rev faster or what? Would gas mileage seriously suffer from such a gear swap? Is there any negative sides in having different gears? Where can you get them? And how hard is it to calibrate the speedo?

What differences do you notice from a gear swap? People say that it's a mind blowing difference and they leave cars behind much much faster. Please clear this up for me so I can fully decide whatever or not to swap gears.

Thanks.

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1989 IROC-Z Convertible
305 TPI automatic
White with black top
Mods:
K&N Filter
Modded air box
My webpage: http://mindspring.com/~humvee

 

the less power your engine has then the more gearing it needs basically.
I have two cars that got faster from switching from 3.7 down to 3.2 gearing. I now run 3.25:1 gears and may go down even more as the car gets faster.
I also have a friend that runs just as fast as I do with 2.73:1 gears.

FYI


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*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
White 1986 Irocz, 305/383 with Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, 3.25:1 rear, Mcreary Road-Stars, SLP-stainless 1.75" shortie headers & Y-pipe, single 3" Borla exhaust, Linginfelter-TPI camshaft part number 74216 pulls 17" vacuum solid. Cam specs 213/219 @.050 114-LSA, .462/.470 lift @1.5:1 ratio. MSD-6AL, billet distributor, multi-retard, blaster-3 coil, and RPM switch.
N/A runs 10.9 @124,
Crack-runs 10.3 @135
haven't run at track since Oct-99

 

I see... but my car runs out of breath around 4,000-4,500 RPMS... Won't higher gears make the car get to that point much faster and make you go slower at the end?

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1989 IROC-Z Convertible
305 TPI automatic
White with black top
Mods:
K&N Filter
Modded air box
My webpage: http://mindspring.com/~humvee

 

Yep,
a higher ratio gear like 3.73:1 will definately do that.

 

Thanks to my 2.73s, mine is a dog off the line, but really comes to life around 3K, I can't wait to put in my 3.73s + posi this weekend.

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'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
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Flowmaster Exhaust,
16" GTA rims,
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-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

The 3.42 gears work great in my '89 IROC with the small-cam 305. The horsepower peak is around 4000 rpm, maybe a tad higher, and I end up going through the traps at 4300-4400 rpm. I gained a couple tenths and a couple mph going from 2.73 gears (which also had a posi with them). I think 3.73's would be too much for my rev-band, and I know some guys with built 350 TPI engines that are running out of revs at the end of the 1/4-mile with those gears. Also, I need the extra mph for the straights on road-race courses where I hit 110-115 mph instead of the low 90's in the 1/4-mile.

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Greg Westphal
'87 IROC 305TPI/A4