Are 355's my best option - Ford Mustang Forum
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post #1 of 55 (permalink) Old 01-02-2012 Thread Starter
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Are 355's my best option

I'm considering changing to 355's from the 331's currently in my car, and wanted to see if these would produce a noticeable increase in performance

The car is my dd and I don't want to lose too much in the way of gas mileage.......and I only use 1st gear on hills. But it is a little slow off the line.

Oh, and anyone got suggestions for a shop somewhere in Austin?

Thanks.

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post #2 of 55 (permalink) Old 01-02-2012
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I have the 355 rear end. I can't compare it to yours, so I am not sure how much of a difference it will make performance wise. But I was getting 24 mpg originally. After getting my Pro Cal tuner and the Flowmaster cat back pro series system, I get 28 on the highway. So I don't think mpg will change much at all.

I just started a new thread as a review for the cat back system. You might want to read it if you were considering an exhaust upgrade. Drone is bad. Real bad.


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post #3 of 55 (permalink) Old 01-02-2012
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If you think it's a little slow off the line get 373's I can't speak to 355's as I've never driven a stang with them. I test drove 315's and my car has 373's.
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post #4 of 55 (permalink) Old 01-02-2012
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running 3.55s with Torsen vs stock 3.31s. Helped me pick up enough RPM to use 5th on front straight at Lime Rock and back straight at Watkins Glen. Now with the ARH long tubes I think I have recovered some torque from 3000-5000 rpm that the car will really jump. I like them, with 26.3" tall race tires they will feel like act like 3.73s on 27" stock tires.
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post #5 of 55 (permalink) Old 01-02-2012
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I am considering this change as well. Thanks for asking and I can't wait to see what people say...

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post #6 of 55 (permalink) Old 01-02-2012
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The truth is a few miles per gallon are not going to make much of a difference on your gas bill. Gas mileage is way overrated. I should know. I drive 50 miles to work, one way, four times a week. I used to have a Toyota Yaris because I thought it was saving me so much money. Well, one day I sat down and actually did the math. Here is how it pans out.

400 miles a week going to and from work. That equals roughly 20,000 miles a year.

At 30 mpg, you will spend somewhere around $2,200 in gas throughout the year.

At 20 mpg, you will spend somewhere around $3,300 in gas. So you save $1,100 during the year. Or $22 bucks a week. Now that seems like a lot, I know. But that is the difference in 10 mpg. Even going from 331's to 373's, you will not drop anywhere near 10 mpg. Maybe three or four.

Now, those numbers are found if you are driving approximately 20,000 miles a year just to work and back. Most people don't drive that much. And there was a 10 mpg drop in mileage, which you wont have. The less you drive, the smaller the price gap.

While saving approximately $90 a month on gas sounds great, you can easily cut that much out of your budget on other things and drive the car you want.

I went from my Yaris and getting 37 mpg to my Mustang getting 24 mpg (now 28 mpg with the cat back). It was a little cheaper to drive the Yaris. I guess you could say I would have an extra $100 a month in my pocket if I was still driving one. But I was driving a YARIS! I am much happier driving my Mustang. I can actually pass people on the highway now. And no one makes fun of my car anymore. The real savings was that the Yaris was cheaper to buy and cheaper to insure. That is where the savings are. But you already have a Mustang. The rear end change will not change your insurance.

So if you want more pep, I would get the 373's. I don't think it will make that much of a difference, either in mpg or performance. But the 373's will be faster than the 355's, and the change might be noticeable if you go from the 331's to the 373's. I bought the 355's to save gas, too. But now I doubt it saved me much at all. Next time I am getting the bigger rear end.

You got the car because it was the best performance bang for the buck on the market. It gets respectable mpg. You won't kill the MPG unless you drive fast and race around town.

If you want the lower rear end, don't pass on it because you will save $10 a month on gas. I say eat at home once more a week and get the hot set up. The only real savings you will have is not changing out the rear end. But you have to have a car you like driving.
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2011 black C/S. Stickers are gone, 5.0 badge in place. Flowmaster cat back Pro Series/Hushpower exhaust that comes with the worst drone in history! FRPP tuner. Drop in K&N filter. Auto Tans I sit in traffic a lot. HID/security package. 3.55 rear end.
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post #7 of 55 (permalink) Old 01-02-2012
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You won't feel a lot of difference between the 3.31s and 3.55s. The Coyote is a revver - I would suggest 3.73s. It's not a radical gear, as Ford offers it stock.

My uncle has 4.10s in his and the MT82 keeps him busy shifting. But it is always "ready to go" with no time waiting to get into the powerband.

If gas mileage is a concern then stick with what you already have.

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post #8 of 55 (permalink) Old 01-02-2012
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I very strongly agree with HEISMANHERSCHEL. Well said, a lot of people don't put things in perspective.
Does my GT use more gas than a Civic?? Of course, I'm not gonna pretend it doesn't. The thing is, who cares. It isn't THAT big of a difference and I get to drive a car I like, and not spend that much more.
Not to mention, I have a 2003 Acura TL as a loaner car at the moment and it is NO better on gas at all. Maybe even worse and it's a V6 import which is supposedly so much better....

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post #9 of 55 (permalink) Old 01-02-2012
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Quote:
Originally Posted by HEISMANHERSCHEL View Post
The truth is a few miles per gallon are not going to make much of a difference on your gas bill. Gas mileage is way overrated. I should know. I drive 50 miles to work, one way, four times a week. I used to have a Toyota Yaris because I thought it was saving me so much money. Well, one day I sat down and actually did the math. Here is how it pans out.

400 miles a week going to and from work. That equals roughly 20,000 miles a year.

At 30 mpg, you will spend somewhere around $2,200 in gas throughout the year.

At 20 mpg, you will spend somewhere around $3,300 in gas. So you save $1,100 during the year. Or $22 bucks a week. Now that seems like a lot, I know. But that is the difference in 10 mpg. Even going from 331's to 373's, you will not drop anywhere near 10 mpg. Maybe three or four.

Now, those numbers are found if you are driving approximately 20,000 miles a year just to work and back. Most people don't drive that much. And there was a 10 mpg drop in mileage, which you wont have. The less you drive, the smaller the price gap.

While saving approximately $90 a month on gas sounds great, you can easily cut that much out of your budget on other things and drive the car you want.

I went from my Yaris and getting 37 mpg to my Mustang getting 24 mpg (now 28 mpg with the cat back). It was a little cheaper to drive the Yaris. I guess you could say I would have an extra $100 a month in my pocket if I was still driving one. But I was driving a YARIS! I am much happier driving my Mustang. I can actually pass people on the highway now. And no one makes fun of my car anymore. The real savings was that the Yaris was cheaper to buy and cheaper to insure. That is where the savings are. But you already have a Mustang. The rear end change will not change your insurance.

So if you want more pep, I would get the 373's. I don't think it will make that much of a difference, either in mpg or performance. But the 373's will be faster than the 355's, and the change might be noticeable if you go from the 331's to the 373's. I bought the 355's to save gas, too. But now I doubt it saved me much at all. Next time I am getting the bigger rear end.

You got the car because it was the best performance bang for the buck on the market. It gets respectable mpg. You won't kill the MPG unless you drive fast and race around town.

If you want the lower rear end, don't pass on it because you will save $10 a month on gas. I say eat at home once more a week and get the hot set up. The only real savings you will have is not changing out the rear end. But you have to have a car you like driving.
Great post. I argue with my inept brother in law all the time about this.
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I got a great deal on my car and it had 331s in it stock..........I went to 373s with the Ford Racing tune and it's a completely different car. I am averaging about 20 mpg at about 60% highway and 40% city, really good considering what it is.

My biggest problem now is traction

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Originally Posted by cudaman ........
Let's hope you don't have the same problem with your zipper and your fueling rod, should you run into another female in a Camaro that needs genetic gas.
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Yeah I would say go with the 3.73's. A 3.31 to 3.55 regear isn't going to net you enough of a change to be worth it. 4.10's may be a bit overkill but 3.73's are well suited for the motor which loves to rev.

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I personally decided to stay with my 3:31 gears. As they are optimal for top speed. If i ever take my car racing for a mile i would like to know that my top end is not hurt but shorter gears.

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Quote:
Originally Posted by RusWolf View Post
I personally decided to stay with my 3:31 gears. As they are optimal for top speed. If i ever take my car racing for a mile i would like to know that my top end is not hurt but shorter gears.
top speed will not be affected you will just be turning a few more rpm's.... and how often are you doing top speed runs?

get the 3:73's and let the fun begin I love them in mine and would not settle for anything less.

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I swapped my original 3.31 gears for 3.55's about 8 months ago, and I've had my car for over a year.

From driving both, I can tell you the difference between 3.31 and 3.55 is not night and day. If you're looking for 'pin you to your seat' at each start than go 3.73.

I contemplated 3.73 but eventually decided 3.55 was the best all-around gearing for me, and I've been happy with the choice. I noticed the change most in the higher gears. My 6th gear, and even 5th in some driving conditions was nearly useless with the 3.31s. The 3.55s improved the overall pull in the higher gears and I did not lose use of the my 1st gear as some have mentioned with 3.73s. 2nd gear starts are also much better.

I lost about 1 MPG average with the gear change. No big deal really.

Also, I have the FRPP power upgrade and it seems this provides the biggest advantage (improved low-end torque) when used with the 3.31 gears. I drove the car with the factory calibration and the Ford calibration after the 3.55 install and difference between the two was not as stark as with the 3.31s.

I think I paid around $160 for the FRPP gears and about $400 for the install. Hope this helps.

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Great reply HEISMANHERSCHEL !
I went from 3.31's to 3.73's in my manual and wouldn't do it again. I got a humming sound and burning smell in the rear after the install. I was also ripped off by the dealer for the install $1000 P&L.
The worst part about 3.31's IMO is 6th gear on the highway.
That alone is worth the upgrade in gears maybe to 3.55's.
I noticed top end loss with the 3.73's which was very disappointing. The overall performance difference was noticeable but nothing major. 1st gear definitely pulled harder and it felt a little snappier in all of the gears in the low rpm's with a top end trade off. The extra shifting was annoying too on my daily traffic filled commute.
I could however see the 3.73's being good with a race tune allowing you to rev higher and having more top end power.

I think 3.55's are the optimal overall gear for this car for the manual.

In the end I got an auto which pulls harder after first gear than the manual with any of the gear choices and couldn't be happier:smilie



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