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Old 06-05-2013, 12:12 PM   #22

GretchenGotGrowl's Avatar
Drives: LFX/F150/Sonic/C7 Z06 ordered
Join Date: Sep 2010
Location: Little Rock, AR
Posts: 6,205
Originally Posted by AmericanMuscleCars View Post
Meaning what I'm not too familiar with the gear systems.
Here is the MPH for each gear at 3800 RPM for the stock 3.27 gear on a A6 V6.

1st: 43
2nd: 76
3rd: 113
4th: 151
5th: 207
6th: 262

At 70 MPH in 6th you are running ~1800 RPM

Now with the 3.91 gear

1st: 36
2nd: 63
3rd: 95
4th: 127
5th: 173
6th: 219

At 70 MPH in 6th you are running ~2200 RPM

You gas mileage will be worse. Your first gear will be just about worthless, and you will probably have to tune it to shift sooner from 1st to 2nd to keep from hitting the rev limiter. That will put you lower in the RPMs when you hit second, below the sweet part of the power band. First fear might be fun with these gears, but it will probably make your car slower, not faster. I would not go above 3.55 on a A6 V6 unless you have something that really bumps up the low-end torque, or you got a custom torque converter to keep you in the power band. In my opinion, it isn't worth the effort until you have built the car to the power you want and you have the right torque converter. When all that's done get the right gear to match your power and output and get the greatest acceleration you can.
EFR Twin Turbo LFX-GPI Tune-ZL1 fuel pump-10:1 CR forged pistons-3.45 gear-Meth Injection-BMR Trailing Arms, Bushings & Sway Bars-CircleD 4000 Stall-GPI Fuel Enrichment System
647 RWHP & 726 RWTQ @18.5 psi on 93 Octane (locked converter)
1/8 mile -- 7.158 @ 102.10 (20psi); old build
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