Rear end gear ratio question
Team Owner
Joined: Jun 2005
Posts: 46,295
Likes: 2,596
From: Northern, VA
St. Jude Donor '15
"In honor of jpee"
Best in what sense? If you mean cruising with the most economy, you can possibly get a lower numerical gear ratio for more mpg, but then it might really bog in 6th. As it is, the 3.42 is about as low as I'd go. As you go higher numerically, you get more oomph, but mileage will suffer some and related rpms go up, which could be a noise factor.
Others will chime in and say that 3.70 is fine, or so is 3.90. That will be your choice.
On a sidenote, I see you're getting a new '09, most likely a take back replacement for the '08 that stalled on your hill?
Others will chime in and say that 3.70 is fine, or so is 3.90. That will be your choice.
On a sidenote, I see you're getting a new '09, most likely a take back replacement for the '08 that stalled on your hill?
Safety Car
Joined: Aug 2005
Posts: 4,279
Likes: 82
From: North Strand, NMB, SC; Retired x 2 (US Army: 70-90 AD) (US Army: 91-16 DAC); yea, I'm old.
Depending on what I am carrying in the back, I average 29.5 - 30 mpg at 75 mph in my '05 MN6 with 4.10s, Vararam SC CAI, tune and ported TB/intake. I will be adding a complete Z06 exhaust soon and having the tune re-calibrated.
You have an extra 30 horses to feed but I would think you should be able to maintain upwards of 28 mpg with 4.10s or even 29 mpg with 3.90.
I love my 4.10s...
You have an extra 30 horses to feed but I would think you should be able to maintain upwards of 28 mpg with 4.10s or even 29 mpg with 3.90.
I love my 4.10s...
Thread Starter
Intermediate
Joined: Jun 2008
Posts: 40
Likes: 0
What are the choices that you can order? Which one would you pick for best highway mileage? Yes, we are ordering a replacement 09 with a stick. 
The 08, (auto) at 75 miles per hour, was 1600 rpm. Thanks for your help.
The 08, (auto) at 75 miles per hour, was 1600 rpm. Thanks for your help.
Last edited by jodenesvette; Sep 2, 2008 at 10:27 PM.
Race Director
Joined: Dec 2007
Posts: 19,574
Likes: 167
From: Frederick, MD
I don't think you have a choice with the manual although the Z51 changes the actual gear sizes in the manual tranny.
Team Owner
Joined: Jun 2005
Posts: 46,295
Likes: 2,596
From: Northern, VA
St. Jude Donor '15
"In honor of jpee"
The stock and only rear gear with the man trans is 3.42. It's fine for me, but others (above and below) may like other gears. I doubt you will want to go to anything numerically lower than the 3.42. 1600 rpm on the highway is truly loafing.
Safety Car
Joined: Aug 2005
Posts: 4,279
Likes: 82
From: North Strand, NMB, SC; Retired x 2 (US Army: 70-90 AD) (US Army: 91-16 DAC); yea, I'm old.
I agree with philies. Unfortunately, in years past you could order different rear axle ratios with the man trans. No more. Only with the auto trans.
The stock and only rear gear with the man trans is 3.42. It's fine for me, but others (above and below) may like other gears. I doubt you will want to go to anything numerically lower than the 3.42. 1600 rpm on the highway is truly loafing.
The stock and only rear gear with the man trans is 3.42. It's fine for me, but others (above and below) may like other gears. I doubt you will want to go to anything numerically lower than the 3.42. 1600 rpm on the highway is truly loafing.
Either stay with the stock 3.42s or you might as well get an Aveo. If the stock gears suit you for highway driving, that's great but if you haven't done so already, take a ride with someone that has taller gears and see the difference.
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Team Owner
Joined: May 2004
Posts: 82,175
Likes: 1,319
From: McKinney TX
St. Jude Donor '21-'22-'23-'24
Here's a chart that shows the difference in gear ratios.--GEAR------Mode--or--Option
------------Z06---Std 6-spd---Z51 6-spd--6-spd Auto---4-spd Auto
--1st-------2.66----2.66--------2.97-------4.03---------3.06
--2nd-------1.78----1.78--------2.07-------2.36---------1.63
--3rd-------1.30----1.30--------1.43-------1.53---------1.00
--4th-------1.00----1.00--------1.00-------1.15---------0.70
--5th-------0.74----0.74--------0.71-------0.85
--6th-------0.50----0.50--------0.57-------0.67
Rev---------2.90----2.90--------3.28-------3.06---------2.29
Axle Ratio--3.42----3.42--------3.42----2.56(or 2.73)--2.73(or 3.15)
Safety Car
Joined: Nov 2007
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From: Bay Area CA
Moderator
Joined: Dec 2002
Posts: 40,891
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From: Lakewood Ranch, FL
Depending on what I am carrying in the back, I average 29.5 - 30 mpg at 75 mph in my '05 MN6 with 4.10s, Vararam SC CAI, tune and ported TB/intake. I will be adding a complete Z06 exhaust soon and having the tune re-calibrated.
You have an extra 30 horses to feed but I would think you should be able to maintain upwards of 28 mpg with 4.10s or even 29 mpg with 3.90.
I love my 4.10s...
You have an extra 30 horses to feed but I would think you should be able to maintain upwards of 28 mpg with 4.10s or even 29 mpg with 3.90.
I love my 4.10s...
I still get north of 25mpg with all my mods!
