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I have been reading the threads about gears and there are lots. But so far they have been about 3.73 or 4.10s. However my needs tend to be less of a hole shot and more towards Highway cruzing. My 2008 came with 3.31s which I understand became standard that year from the old standard of 3.55s. The difference is about 8%. There must be a reason the Ford engineers picked the 3.55s on the early S197s. I would expect to feel a little more push when getting on the freeway and pulling away from stop lights. It seems like it would be a better gear all around. What is the effect on MPG? Also, browsing for information I found some 3.55 new take off gears which fit 2005 to 2007 8.8 rear ends. What changed in 2008 about the gears?
 

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3.31s are standard on all mustangs except for the bullitt and gt500kr which come with 3.73's. 3.55's are optional for the manual mustang gt's.

IMO, and i'm not just trying to make you get more "power", go with the 3.73's because the 3.31's to 3.55's won't even be a big enough of a difference for you to notice it
 

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I changed to 3.73 from 3.31 as well & I couldn't be happier, not that much of a higher rev & I do a lot of Interstate driving. Like hotshot said, you're basically wasting your money with going with 3.55's.....probably won't notice much if any difference.
 

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If we weren't 1500 miles apart, I'd trade you for my 3.55's. I am real close to 30 mpg on the highway, 20-22 in town.

Frank
 

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If you have a manual, get 4.10s. If you have an auto, then 3.73 would be good. Who ever says 4.10s is not a highway gear probably has never driven in a mustang with 4.10s. In about a week, I drive about 300 miles on the hwy.
 

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ONLY on 07-up. 05 and 06 had 3.55's standard on manual trans cars

3.31s are standard on all mustangs except for the bullitt and gt500kr which come with 3.73's. 3.55's are optional for the manual mustang gt's.

IMO, and i'm not just trying to make you get more "power", go with the 3.73's because the 3.31's to 3.55's won't even be a big enough of a difference for you to notice it
 

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Who ever says 4.10s is not a highway gear probably has never driven in a mustang with 4.10s. In about a week, I drive about 300 miles on the hwy.
People get used to prison too. But that doesn't make prison nice.:scratchchin
 

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I have been reading the threads about gears and there are lots. But so far they have been about 3.73 or 4.10s. However my needs tend to be less of a hole shot and more towards Highway cruzing. My 2008 came with 3.31s which I understand became standard that year from the old standard of 3.55s. The difference is about 8%. There must be a reason the Ford engineers picked the 3.55s on the early S197s. I would expect to feel a little more push when getting on the freeway and pulling away from stop lights. It seems like it would be a better gear all around. What is the effect on MPG? Also, browsing for information I found some 3.55 new take off gears which fit 2005 to 2007 8.8 rear ends. What changed in 2008 about the gears?
You have the ability to answer your own question. Don't simply listen to some dork that says you "need X.XX gear because they ROCK!" For all you know they are borderline brain dead. Just because they don't mind driving around with the motor spinning to the moon doesn't mean you won't.

This is the most important informatio you need before making your own choice based on your situation:

What RPM’s do you want to be cruising down the freeway at and at what speed. Think about that hard, and go drive the car. Drive it for 2 miles at 3,000rpm…..it will most likely drive you crazy. If it does, you want to make sure you don’t get a gear that will put you in that range. I have mine set up to run at 2400rpm’[email protected] I wouldn’t want to spin it any higher than that even if it costs me a bit of acceleration.

Dependig on what the height of your tires are I'll bet you will want 3.55's or 3.73's to get a comfortable cruising RPM.

I run a 3.55 and couldn't imagine wanting to gear my car shorter than it is. I do have a screw blower though. 1st gear is worthless, I just punch it and have to shift right away and 2nd gear will haze the tires even though I have some seriously sticky rubber. Shorter gearing wouldn't get me going any faster....faster. It could possibly even slow me down.

Even if you don't have a blower but have stock-ish tires (high performance, all season about 235-245mm wide) you will still light the tires up something good in first and have to go for second super fast which makes that gear borderline useless. You will still lightly spin the tires most of the way through second too (if you make the 1-2nd gear shift fast) which lessens the efectiveness of that gear too. Which will slow you down.

Whe I had my stock 3.31's and stock Pirelli tires (about 75 miles:D) I could SPIN the tires all the way through 2nd gear if I wanted too.

Use this gearing calculator. It will help you pick a gear for your situation. Use the # .68 for the trans ratio. You will also need to measure the height of your rear tire at the right pressure sitting o the ground. You can keep firing numbers in till you find the gear that gets you the cruising RPM that you are looking for.

http://www.angelfire.com/fl/procrastination/rear.html

Oh yeah.......NEVER BUY A USED GEAR!!!!!
 

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I agree with Sqidd. I have 4.10s and this past weekend went on about a two hour interstate drive to the lake. I zinged along happily in the fast lane at 85-90mph the whole time which is about 2900-3100 rpm. I didn't mind it at all. But that doesn't mean you won't. Get out and use fourth gear to find an rpm range you would like to cruise at and choose using that as a guide. If you even have to ask about highway driving, go 3.73s. I lost about 1-2mpg with the 4.10s over 3.55s.
 

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Squidd, thanks for that calculator link. I'm kinda' in the same boat: 3.31s, but looking to upgrade at some point. Looks like if I select the 3.73s, I'll have to turn an additional 200 rpms in 5th gear to maintain the same cruising speed. That's not too bad.

BTW, so no one else has to look it up, for the GT you will use ".68" for the transmission gear ratio (5th gear), and for the stock 17" Pirelli's, the tire diameter is 27.2".

~HA
 
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