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Alright. Seems all I do is read up, study, and ask questions here. Anyways, is an upgrade in gears from a stock 3.31 to 3.73 worth it (after shop install costs (500-600$)?

So far I've done a C&L Racer CAI/Breenspeed tune. Borla axelbacks in my 2006 Auto GT. Basically I want more torque, more power to the wheels, and better pulling power/throttle response. Is this the next mod I should go for to achieve this? Also if I do will I need to re-order a tune to compensate for the difference?

Thank you to everyone again for any help.
 

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Depends if $600 is alot of money to you, but personally I think it would be worth it. I would assume a re-tune would be necessary, but I'm not 100% sure.
 

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go 4.10s!

500-600 install is toomuch to double.


i paid $300
 

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So. The gears will be worth it. I'll be able to put the pedal down some at 1800 rpms and get a kick back feeling...even with an auto...

I heard 3.73 for auto's and 4.10 for manuals.
 

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you mean 4.10 auto 3.73 manual?


lol

thats usually how it goes.


im going 4.10s on my manual now
 

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So. The gears will be worth it. I'll be able to put the pedal down some at 1800 rpms and get a kick back feeling...even with an auto...

I heard 3.73 for auto's and 4.10 for manuals.
Firstly its not that simple, there are a lot more variables to consider. Secondly even if there werent it would be the other way around.

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 information 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.


Depending 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 ) 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 # .71 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.htmlhttp://www.angelfire.com/fl/procrastination/rear.html

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

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Firstly its not that simple, there are a lot more variables to consider. Secondly even if there werent it would be the other way around.

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 information 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.


Depending 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 ) 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 # .71 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.htmlhttp://www.angelfire.com/fl/procrastination/rear.html

Oh yeah.......NEVER BUY A USED GEAR!!!!!
Well said; +1 from top to bottom.

Except for the "used gear" part. I do agree with not buying used gears from someone/some car whom you don't know, but I had a set of 3.73's in the rear end of a fox I used to have. The fox met its maker one day when I was racing an old school, boosted, AWD Eclipse. I was on street tires, and the rear broke loose on me when I shifted into 3rd and ended up going over a curb and ended up in the lanes of oncoming traffic. I flexed the chassis, cracked my oil pan and transmission case, and pushed the front driver's side tire and suspension into the firewall. I pulled everything out of the car that was usable, including the 8.8 rear-end with the 3.73's. Those are the same 3.73's that are in my car now almost 6 years later. No whining, humming, or problems to date.
 

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I'm running FRPP 3.73N's and it really woke my automatic up! As an example: I now hit 60 mph at @ 2000 rpm, which used to be @ 65 mph with the 3.31's. Consider the information offered, crunch your numbers (3.55 vs 3.73 vs 4.10), and then find a shop that's not so damn high. I got my gears and UD pulleys done at Excessive in Manassas during a holiday special. Concur with the skip the used gear idea!!
 

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I put FRPP 3.73's in my former 06GT and they did much better than the 3.31's but still not what I expected and wanted from my auto. When it came time to change out the wifes gears last year on her GT Vert, I went with the FRPP 4.10's. The vert being heavier and not as modified as my former, I believed the 4.10's were the right choice for some added giddyup. I was right, the 4.10's were a good choice and woke up the vert. At 70mph the tach is around 2650, which is just fine. Before, the car could barely bark the tires...now...it lights them up, meaning I'm getting more hp and tq to the wheels quicker.

As Sqidd said, it all depends on what you're looking for.
 

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GT automatic transmission ratios

Had to dig around a bit, but here's the stock 2009 GT automatic transmission ratios:

3.250:1 first gear ratio
2.440:1 second gear ratio,
1.550:1 third gear ratio
1.000:1 fourth gear ratio
0.750:1 fifth gear ratio
 

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0.750:1 fifth gear ratio
Everything I found had it at .71

Where did you get to that data? I would like to know what it realy is.
 

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At 70mph the tach is around 2650, which is just fine.
That would drive me insane!:happyhapp:D and to be stuck at 70 would drive me nuts too. I don't know what is normal about where you are from but normal traffic speed in MI is 80mph. That would be a little over 3000RPM's up here. I would't want to go 10 miles like that. And there is no way I am going to do 70mph;)
 

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That would drive me insane!:happyhapp:D and to be stuck at 70 would drive me nuts too. I don't know what is normal about where you are from but normal traffic speed in MI is 80mph. That would be a little over 3000RPM's up here. I would't want to go 10 miles like that. And there is no way I am going to do 70mph;)
lol who actually drives the speed limit now a days? if ur under 75 in atlanta ur getting flicked off. fast line is like 85 MINIMUM. The speed limit is just a suggestion :D
 

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I vote for 3.73's for an auto. First gear goes by in an instant, especially if you add more power in the future. You will feel more difference in the gear change that all the other mods you have done to date:bigthumbsup
 

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lol who actually drives the speed limit now a days? if ur under 75 in atlanta ur getting flicked off. fast line is like 85 MINIMUM. The speed limit is just a suggestion :D

75 is still border line runn your as...butt off the road.
 

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i have a 06 gt and 410 gears and it is the best mod i have done.it has crazy power now at any time any speed. matter of fact if it was not my dd i would love to have went with a higher number gear.and at 80 mph i am a little below 3k rpms.autos go with 410 gears unless you do a lot of highway 80+mph driving for long periods at a time. words cant decribe how much better these autos perform with 410 gears.
 

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Everything I found had it at .71

Where did you get to that data? I would like to know what it realy is.
From Motortrend's web site:

2009 Ford Mustang GT Coupe Options

http://www.motortrend.com/cars/2009/ford/mustang/gt_coupe/816/packages_options/index.html


5-Speed Manual Transmission - $0

Manual five-speed transmission with shift lever on floor, 3.340:1 first gear ratio, 2.000:1 second gear ratio, 1.320:1 third gear ratio, 1.000:1 fourth gear ratio, 0.670:1 fifth gear ratio and 3.380:1 reverse gear ratio Tremec 3650; Standard transmission; Excludes: [44L] 4-Speed Automatic Transmission

4-Speed Automatic Transmission - $645

Automatic five-speed transmission with lock-up, electronic control, shift lever on floor, 3.250:1 first gear ratio, 2.440:1 second gear ratio, 1.550:1 third gear ratio, 1.000:1 fourth gear ratio, 0.750:1 fifth gear ratio and 3.070:1 reverse gear ratio 5R55S; Excludes: [44K] 5-Speed Manual Transmission

I'm guessing the 5th gear ratio on the 4-speed automatic is when it's in overdrive.
 

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I'm going to be updating my gears in the next 2 weeks. I have a 2008 Automatic GT with stock 3.31 gears.

With my stock Pirellis and my 3.31s, I'm spinning 2,450rpm at ~80mph.

Off to the calculator at http://www.angelfire.com/fl/procrastination/rear.html

I used 0.75 for my transmission gear ratio, and 27.2 for my tire diameter in inches.

If I just change the gears to 3.73s, I'll spin 2,750rpm at ~80mph.

If I just change the gears to 4.10s, I'll spin 3,040rpm ay ~80mph.

I took Jason's advice and drove for a bit yesterday where my RPMs were just at about 3,040, and there's NO WAY I'm gonna do that all the way to work and back home for almost 2 hours every day! But 2,750 was OK :)

So, it'll be 3.73s for Sam. Thanks for the great advice Jason... Again :bigthumbsup
 
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