Hi everyone,

I'm new to mustang mods and I decided to upgrade my 2014 V6 6AT stock gear ratio from 2.73 to 3.73. I know a speedometer correction is required but I live in California and am afraid the use of a tune to adjust the speedometer would fail me the future smog test. I did some research and found the only tune that can pass the smog test is Ford Performance ProCal Tuner, but it seems like only fit the 11-14 GT.
Now is there any way I can adjust my speedometer and still pass the smog with no problem?
Thank you so much!

 

Welcome to TMS Charlie!

Hypertech Offers Both Speedometer Calibrators and Tuners That are California Smog Legal. Also the Dealer Can Change Speedometer Calibration.

I live in Ca. I feel Your Pain!~

https://hypertech.com/pages/product-..._3-7l-v6-gas-m

I would Get the Tuner! After All you Want to GO faster or You Would Not Have Changed the Gears!

KC

 

Dealer can only change it to a gear ratio that was available for your car, so the 2.73 or 3.31 so get the tuner as long as it is CARB legal.
Welcome to the Source Charlie

 

Are we Speaking Legally?? Or Not At All??

KC

 

if you only change the gear ratio in the tune (don't change anything else), it should not cause the car to fail emissions (as far as I know!)

 

Some California Emissions Test Run Car on Dyno. Now Being Singled Out & Having Had to go To Inspection at a Referee Station Myself in California I also tend to Be a Bit Paranoid About Inspections! 100 Mile Round Trip BTW. But I'm Unsure if that Speedo Issue would Be Caught. If you Go to Referee for Issues They Look over Car Top to Bottom. Luckily I had Nothing Other Than a Stuck Tune and Had Already Had a Ford Tech Download a Stock Tune.

I had the First Bama Gt-500 Tune & C&L Intake. If I had Known Ford Racing Was Coming Out With a Cold Air & Tune That was Carb Legal I would Have Waited. These Days Stock is Fine For Me!

His Speedo Needs to be Corrected Anyway It's Gotta Be Way Off! But I get Your Point.

KC

 

I know someone that had 3.73 gears done at Ford the local Ford Store and was told that, V6 2.73 or 3.31 and the GT 3.15, 3.31, 3.55 or 3.73. Only the gears that those models could actually get from the factory. I guess that falls into the same category as tire sizes on the F150, if it is not an option Fords IDS cannot do it.
I have not looked into it on any Mustang Changes but that is something that ForScan can do on the F150's.

 

Inquiring Minds Want to Know. I'll Run it By Ford Tech I call in a Pinch Next time I Talk to Him. I know on the Trucks they Would Change Tire Sizes up to a Point and Then we Had to Use a Little Add On Calibration Device When Huge Tires Were Used. This Guy Needs a Cal Legal Tune Anyway. You Don't Change Gears Unless You Want to Go Fast. Or Quick in this Case! I'm Getting Rusty on the Service Side. Been Away Too Long! A Case of CRS Don't Help! It looks Like He Popped in Right after My Post! Which was in the Wee Hours! We May Not See Him Again!

KC

 

I had to Call My Tech for Another Question and Went Ahead & Asked about Speedo. You Were Spot On! Thanks For Catching That! It is Appreciated! We All Miss a Gear Now & Then!

KC

 

Not a problem KC, that is part of being stuck in this family

 

Your Welcome Brother!

I bet he Has a Hypertech Tuner On the Way!

KC

 

Thank you! My local dealers aren't too smart about this information, but I'll try a few calls Monday. Do you know if the pro cal tuner fits the V6 or only the GT?

 

Thank you!
I saw the Spectrum California Edition tuner and the Speedometer Calibrator both have CARB. But I wonder if the gear change would require a tune or only require a speedometer calibrator. Am I right to say that a calibrator is enough to adjust for transmission and speedometer and a tune is just for faster adjustment but not necessary?

 

For $279.00 You Can Adjust Your Speedometer. Thats It And Check DTC'S
For $379.00 You Can Gain 15 HorsePower And A Whole Lot More.
For $400.00 You Can Gain 15 HorsePower And A Whole Lot More.

{You Need To Read Instruction Manuals on All } & Make a Decision. Your Gonna Spend $279.00 Anyway. 15 Horsepower For $100.00 to 120.00 Is Cheap. You Can Pick Up Fuel Mileage As Well. Check Out All Info Available! Note The Hypertech is on the V6 Page!

We Don't Believe Dealer Can Set to 3.73 Because they were Not Available on V6 From the Factory. Probably Charge a Couple o Hundred Buck at Least If they Could Even Do it!

Not a Fan of Procal. And I am A Ford Guy!

BTMO. If Anybody Has Further Suggestions. I have Had Insomnia Last two Nights So I Am Out Of Gas! SERIOUSLY I'M HAVING TROUBLE STAYING AWAKE! Got to Go!

KC

 

be careful -- those tunes that claim to gain horsepower or improve mileage are the ones that also might mess with other settings that will cause you to fail emissions -- for example it is very common to turn off the rear O2 sensors, I don't know why they do it, but that will fail emissions for sure

but with most tuner devices, I believe you can just reset the rear gear ratio without changing anything else, and that "should" be safe for emissions

I guess a "speedo recallibrator" is a dumbed-down tuner that can only change the rear gear ratio setting; if so that should be safe also

 

I'm Curious Why the Gear Change? Was it For Performance or Simply a Replacement for the Other Ratio Failing?

KC

 

It is for performance. I did some research and seems that this should be some improvement(from 2.73 to 3.73). I'm unsure about any tune because of the smog problem, a speedometer calibrator is what I will try after the gear change is done next week. I will try to do as little as possible to the PCM because for me it's just a pain to fix any emission test fails in CA. But thank you for the helpful price comparison and information!
I'm also getting an axle-back Borla S-type next week, hope it sounds as nice as the price.

 

I'm unsure about most tuner devices, but I asked SCT whether I can only change the speedo and got a reply that says "it will have 3 power levels, based on octane. 87, 91 and 93 octane tunes."
So, probably not? Lol

 

Any tuner that does not have the CARB approval will not pass smog whether you changed anything else or not.
California is bad enough I had to go to the Referee with a car that was better than stock on all emissions but did not pass visual, this was 30 years ago so I could only imagine now.

 

They are talking about the "canned tunes" that come with the tuner. These "tunes" modify various things and might cause problems with emissions, depending on what they change in the tunes. I would avoid loading those tunes, if I wanted to avoid potential problems with emissions.

With SCT, the way it works, is you load a tune and you can modify some parameters when you load the tune. So you would modify the rear gear ratio before loading a tune. But the problem is, you need to load a tune that does not make any other changes. I am not sure if you can download the factory tune from the car, modify the rear gear ratio only, and then load it back. That would be a good question for SCT, if you want to ask them.