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Discussion Starter #1 (Edited)
Hey guys,

I have a 2013 3.7L v6 automatic Convertible. I have had this car for about 4 years and I have 95k on it now. The car has the stock 2.73 rear gears on it. The car has always been incredibly slow to get up to speed, and when I bought it I didn't understand much. In other words bad acceleration. I have done numerous things to try to correct this over the years...

- I have an aftermarket cold air intake.
- I have a pedal commander to improve the throttle body response
- and I have a Bama tune from American Muscle.

None of these things have really improved the acceleration on this car and after reading, people say that I should swap out my rear end gears.

So I have some questions. I called some places and they recommended that I put in the 3.73gears to make the car more fun without gas mileage taking a big hit.

1) How much will this affect my gas mileage? I'm getting about 20mpg combined driving around Long Island NY with the stock 2.73gears.

2) Will my car get less traction if I do this. As this is my daily driver it still needs to have traction in rain and snow.

3) Will it make the car accelerate smoother then the 2.73 gears or will it be jerky as if there is less throttle delay?

I made an appointment to do the gears on Friday the 26th. I really want to know if I'm doing the right thing before I go through with it. Please give me some feedback on this.

Thanks all! Looking forward to your responses.
 

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If your only getting an average of 20 mpg with your 2.73 gears, 3.73 won't hurt you too bad :). Traction will be the same except you have to be more gentle with the gas pedal :). I went from the factory option 3.31 gears to 3.73 and love them :). Good luck and I hope the people installing your gears know what they are doing...…………….
 

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Discussion Starter #3
Yes I have a proshop here on Long Island called Mustang Magic that works specifically on these types of jobs. I am a little concerned that the driveshaft could have issues. People say it has a 115mph limit and that would be based on the stock gears. If its spinning twice as fast would that lower the limiter? Would I be better off with 3.55 gears or stick with the 3.73?
 

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Mustang Magic is still around LOL?

The question is, is the juice worth the squeeze? The car will FEEL a little faster but in fact won't be much faster. And yes gas mileage will certainly be affected.
 

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Discussion Starter #5
Mustang Magic is still around LOL?

The question is, is the juice worth the squeeze? The car will FEEL a little faster but in fact won't be much faster. And yes gas mileage will certainly be affected.
Is it worth the squeeze in what regard. The difference between 3.55 and 3.73 or the difference between the crappy 2.73 stock ones I have versus all of the above?

Right now based on peoples responses I'm actually leaning toward doing the 3.55. I have stock 225 tires. I have stock drive shaft. I have 95k miles on the car and I am going to replace the tires soon but I am not replacing the rims too. Definitely don't want to invest in a drive shaft. I just want my car to accelerate as good as a Ford Explorer next to me at a red light. The 2.73 gears have been like having a speed limit restriction until the car gets up to 80mph.
 

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Mustang Magic is still around LOL?

The question is, is the juice worth the squeeze? The car will FEEL a little faster but in fact won't be much faster. And yes gas mileage will certainly be affected.
Is it worth the squeeze in what regard. The difference between 3.55 and 3.73 or the difference between the crappy 2.73 stock ones I have versus all of the above?

Right now based on peoples responses I'm actually leaning toward doing the 3.55. I have stock 225 tires. I have stock drive shaft. I have 95k miles on the car and I am going to replace the tires soon but I am not replacing the rims too. Definitely don't want to invest in a drive shaft. I just want my car to accelerate as good as a Ford Explorer next to me at a red light. The 2.73 gears have been like having a speed limit restriction until the car gets up to 80mph.
Lol, mine’s a 12 coupe auto and I’m looking for gears as well. I’ve narrowed it down to the 3.31’s because I do 100 miles round trip (95% hwy) a day at 75-80mph. I was bouncing around the idea of 3.55 and 3.75 but I think their too short for how I use my car.

The speed limit on the stock driveshaft i think is 135, it explodes. From what I’ve read is that upgrading the driveshaft is not “required” unless your pushing a lot of hp or remove the speed limiter. When I got my car tuned I asked them to move the limiter to 120.
 

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3.7 rear gears

I have a 94 3.8 v6 that I imagine is slower than yours @ 145hp. I changed to 3.73 gears with posi. It really woke her up. Still no rocket, but at least now I can tell when I push down on the gas pedal! I do not regret the posi either!
 

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The stock driveshaft limit is 135, which is why the limiter is set to 130mph. If you change gears, the mph limit gets lower based on how steep the gears are that you choose. I highly recommend a driveshaft also as insurnace. I know its expensive. I like my 3.55's but sometimes I wish I choose 3.73's. But I chose 3.55 for the fuel milage tradeoff. If fuel milage isn't as much of a concern, choose 3.73. And do the driveshaft if you plan on going faster than 100mph!
 

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Discussion Starter #9
The stock driveshaft limit is 135, which is why the limiter is set to 130mph. If you change gears, the mph limit gets lower based on how steep the gears are that you choose. I highly recommend a driveshaft also as insurnace. I know its expensive. I like my 3.55's but sometimes I wish I choose 3.73's. But I chose 3.55 for the fuel milage tradeoff. If fuel milage isn't as much of a concern, choose 3.73. And do the driveshaft if you plan on going faster than 100mph!
Thanks, I'm learning toward the 3.55 ratio though because I am not upgrading the tire sizes or driveshaft, too much money to invest on my 2013 with 95k. I'm also not looking to drive faster than 100mph (usually 80 is my max speed.) I just want my mustang to be as peppy as the honda civics driving next to me on the road and not get passed by a half a mile every time a light goes green lol. I live in the NYC metro area and do most of my driving around Long Island. Its flat and full of traffic and red lights. After reading your responses it seems that the 3.73 can go through the gears a little too fast as the 2.73 I have go through them too slow. I just need a good balance, I don't want to sacrifice alot of milege either because everyone says the 2.73 is so good and I get 17-20mpg on those in this area, perhaps that is because of the stop and go all the time. But again without test driving the different ratios, this is all a guess game for me and I'm an amatuer just trying to get this right lol. Depending how I like this gear change will determine if I buy another mustang too because the base version of the one I have should have been quicker given the horse power.
 

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cdengris, I've owned 4 Mustangs over 25 years ('87 5.0 LX 3.55, '88 GT 3.73, '99 Cobra 4.10/4.30, '13 V6 3.55). I've changed gears on every single one based on what I was doing with each car. Gears make it more fun to drive without going crazy on horsepower $$$.
 

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Discussion Starter #11
cdengris, I've owned 4 Mustangs over 25 years ('87 5.0 LX 3.55, '88 GT 3.73, '99 Cobra 4.10/4.30, '13 V6 3.55). I've changed gears on every single one based on what I was doing with each car. Gears make it more fun to drive without going crazy on horsepower $$$.
So would you recommend those 3.55 gears for my 13 convertible v6?
 

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Convertibles are a little heavier and typically would go 1 gear choice higher. If you’re not going to do any other mods, just go with 3.73 and be done. You’ll love it. Air down your rear tires to 30-32psi and enjoy.
 

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So would you recommend those 3.55 gears for my 13 convertible v6?
Stick with the 3.55 you were thinking of, those will probably be a good gear for what your after. You sound like you want some more fun but not a drag racer. 3.55 will be a better gear for highway driving and still give you get up and go. I have a lot of experience with gear ratios on these 3.7 Stangs.

FYI I’ve had 3.31, 3.73, 4.10’s NA and now 3.55’s (doing a custom M122 with custom aluminum manifold and cooler soon) on my base 13 performance pack car. I also had my car turbocharged in 2015 and put my 3.31 gears back in for that.

Also if your car is an automatic swap to More Power Tuning (MPT), as they have the absolute best tuning for the 3.7 automatic cars, no other tuners comes close (I’ve had Bama, Lund and MPT with my automatic car). I been using MPT now for 6 years.
 

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Discussion Starter #14 (Edited)
Stick with the 3.55 you were thinking of, those will probably be a good gear for what your after. You sound like you want some more fun but not a drag racer. 3.55 will be a better gear for highway driving and still give you get up and go. I have a lot of experience with gear ratios on these 3.7 Stangs.

FYI I’ve had 3.31, 3.73, 4.10’s NA and now 3.55’s (doing a custom M122 with custom aluminum manifold and cooler soon) on my base 13 performance pack car. I also had my car turbocharged in 2015 and put my 3.31 gears back in for that.

Also if your car is an automatic swap to More Power Tuning (MPT), as they have the absolute best tuning for the 3.7 automatic cars, no other tuners comes close (I’ve had Bama, Lund and MPT with my automatic car). I been using MPT now for 6 years.
Thanks for your feedback. Yes you are right I am just looking to make the car more fun (the way it should have been.) I didn't even know anything about gear ratios until I bought the car and realized my Mustang is slower to start then all the cars next to me.

The 3.55 sound like the best balance. I don't want to do any other upgrades really as this car has 95k and I need new tires next (im not upgrading the rims.)

The cons I see with the 3.73 include...
- Driveshaft issues with the limiter.
- It pulls through gears too quick which can potentially lose traction. (bad in rain and snow)
- Loss of MPG on highway.
- Stock tires may be too small

On the flip side the pros seem to be,,,
- My 3.7 is a convertible (maybe it helps the extra weight move?)
- Highway MPG won't matter much anyway in a high traffic metro area.
- The first gear pull isn't as different from the 3.55 as everyone says

So that's what I've come up with as a amatuer making this step forward haha. Would have been nice if Ford just made the car correct to begin with. The 2.73s have been horrendous especially when I'm in 10-20mph traffic and the car bucks.

In terms of tunning i appreciate the advice there but I have a bama tune that I bought from American Muscle and it is free tunes for life. That thing ran me like $400 and didn't really solve the problem because I've only used it on the stock gears. Be interesting to see how it improves with new gears.
 

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Bama gave out free tunes for life because....well....frankly it will take them that wrong to get it right.

You will need an update on your tune from them for the gears which frankly I think is a waste of money.
 

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MPT tunes only. He's not kidding. There is no other choice! You already have the tuner, you just need the tune which is $99 (MPT Mustang tune).
 

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Discussion Starter #17 (Edited)
So they can put their tunes on my bluetooth SCT tuner? If thats the case and these guys are as good as you guys are claiming I would consider it.
 

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https://www.morepowertuning.com/scttech

Here's their tech support page. Which SCT do you have?

MPT is pretty good. I have their 91 PRX with shifting tune and it's great! You will still need gears because it doesn't fully help that. It doesn't come with "tunes for life" but if you want to add stuff to your tune it only costs $25 to update. I also did away with my Pedal Commander when I got this tune because the throttle response and driveability is so good. I hope this helps!

---------- Post added at 09:48 AM ---------- Previous post was at 09:48 AM ----------

https://www.morepowertuning.com/scttech

Here's their tech support page. Which SCT do you have?

MPT is pretty good. I have their 91 PRX with shifting tune and it's great! You will still need gears because it doesn't fully help that. It doesn't come with "tunes for life" but if you want to add stuff to your tune it only costs $25 to update. I also did away with my Pedal Commander when I got this tune because the throttle response and driveability is so good. I hope this helps!
 

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Discussion Starter #19 (Edited)
Alright so I got the 3.55 gears put in yesterday guys and I loaded the BAMA tune that I called American Muscle to make up for me. My initial thoughts are.... MEGA DISAPPOINTMENT. The car slightly has better acceleration but its so minimal that it seems this wasn't worth all the money I just laid out. I mean every other modern car accelerates from a red light smoothly and quickly too, and they aren't supposed to have the power my mustang has. I've driven rental cars that are Fords Focus's and quicker then the stang to get going lol. I'm hoping that its because this tune just sucks and that I can correct this with a proper tune. The acceleration is barely noticeable until I get up in speed. Its slightly smoother through first gear in traffic and parkinglots but after that it's still that jerky feeling the 2.73's always had. I really have to hit the gas to get the RPMs to go up on a short distance quick acceleration which is only something I would do hard if I need to do an emergency merge, which I did once today. I only drove around town today. Lots of in and out of the car at stores so I got roughly 14mpg which is pretty bad but I'm sure that will go up when I do real combined driving all week.

I thought once I did this I would get rid of the pedal commander too for the throttle body response sensitivity but right now it seems that I may need to keep that.

With all that being said it seems the install itself went well and the car is acting normal. No additional noise or anything, this is just a performance thing for me.

The tune could be an issue. I will look into it this week but any other recommendations. Is it me?
 

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You might need to drive it easy for a little while and let the car learn the new gears and tune. Also isn’t there a break-in period when putting in new gears?
 
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