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Old Fart
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171 Posts
Discussion Starter #1
Do you like the change?

How much did it hurt traction coming out of the hole?

How bad did it hurt gas mileage?

Thanks, L.L.:patriot:
 

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Owns 3 GTO's
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16,515 Posts
I have been thinking of 3.91's. I need to get in the diff soon anyways. I would like to see the outcome here before I choose which gears though.
 

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Captain Thread Killer returns
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21,898 Posts
FI05Goat said:
Yeah I would be interested in what 3.91s would do in a Maggie car.
you'd probably be sideways for the 1st 1/8 mile
 

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Born Again Goat
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1,555 Posts
I'm running 3.73s with a M6 and getting 21mpg combined with my 408. As to the move from 3.46 gearing, I was looking for a better rpm thru the traps...any further adjustment will be made with tire diameter. I'm currently running MT drag radials and traction is not an issue. I would think that Nitto drag radials would provide good street manners and traction as well.

Stickier tires would take care of the "sideways thru the 1/8th" issue, if it actually existed.
 

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Owns 3 GTO's
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16,515 Posts
GoatChs said:
I'm running 3.73s with a M6 and getting 21mpg combined with my 408. As to the move from 3.46 gearing, I was looking for a better rpm thru the traps...any further adjustment will be made with tire diameter. I'm currently running MT drag radials and traction is not an issue. I would think that Nitto drag radials would provide good street manners and traction as well.

Stickier tires would take care of the "sideways thru the 1/8th" issue, if it actually existed.
What are your rpm's at 75mph in 6th?
 

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Born Again Goat
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About 2100.
 

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god of the sea people
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229 Posts
Dbluegoat said:
you'd probably be sideways for the 1st 1/8 mile
some of us do that on purpose.............
 

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408 Posts
I had the 373s put in our 06' M6 car as an overall improvement. I felt the car was not in a very efficent range while in high gear(6th) at the speeds we usually go..wife and i. In fact, the display showed better MPG in 5th so that was part of my selling point given to her;) . I also felt that being as this car will only accept so big of a rear tire and i didnt want to be short shifting in the intersection had i gone 391s, that they would be a decent middle of the road improvement. I was right. I also had the communist (skip shift)function removed.
 

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Where are you getting the 3.73's from? I was told 3.91 was the next step.
Joe
 

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Member #804
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5,539 Posts
Had 3.91 Kaaz in my car when I was headers only, made it very fun driving, did 1.7x 60'

Driving to AMES gto meet it did 22mpg
Driving to Indy for us nationals with 402ci and 3.91 gear my GTO did 21 mpg (according to the cluster).
 

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1,249 Posts
I got the 3.72 w/ kaaz. Like them for what I do (road racing and autox). I have no idea right now on economy since I haven't had my speedo fixed from the gear install yet.
 

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Quest for 10's Continues!
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3,561 Posts
Speaking from an M6 standpoint I love the 3.91s. Made the car a heck of a lot more fun to drive around town, they made 5th and 6th more useful on the highway and MPG doesn't change much, if at all!

Oh yeah and :gears:
 

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burnout silver star award :)
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2,166 Posts
i wonder how much difference it would make performance wise if i put 3.73's behind the 408...
 

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Born Again Goat
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1,555 Posts
Muff Daddy said:
i wonder how much difference it would make performance wise if i put 3.73's behind the 408...
GoatChs said:
I'm running 3.73s with a M6 and getting 21mpg combined with my 408. As to the move from 3.46 gearing, I was looking for a better rpm thru the traps...any further adjustment will be made with tire diameter. I'm currently running MT drag radials and traction is not an issue.
I wonder as well...
 
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