djoneill

I just talked to the service writer at the dealership where I bought the car, and they say they can't install 3.31 gears on my '12 v6 convertible with 6MT.

I wanted to install the gears myself (or have them installed at a driveline shop) and have the dealership recalibrate the speedometer. Since the car is new, I was hoping to avoid flashing the car with an aftermarket tune.

I was under the impression that since the 3.31s came stock with the performance package (or in Canada), that it was a simple flip of a switch.

Any advice how to upgrade the rear to 3.31 and not risk the warranty?

Thanks!

Chromeshadow

Try another dealer. I have a 2012 V6 manual trans, I requested the 3.31s when I ordered the car, they are a common option.

hogasswild

You're oversimplifying it. The dealer will try to sell you a new PCM which is very expensive. You're way better off going to a reputable shop that specializes in Mustangs and gear swaps. Ironically, the more experienced one tend to charge less because it takes them less time. After the install, get a tuner to recalibrate for the right gears. You may also want to consider 3.55 or 3.73 gears while you're thinking about doing it.

alkemist

If you are going to upgrade your rear end and want to have some fun, go with 3.73 or 4.10.

snaf2u

Not with the vert, at least when I got my `11. 2.73`s only gears to be had. I tried to get 3.31`s but neither the dealer or a local shop was able to obtain Ford Racing 3.31`s. There were none to buy. Hence the 3.55`s with which I am happy.

scottybaccus

My dealer agreed to code the new ratio for $70.
I picked up a set of new take out OE Ford 3.31 gears from Shelby American for $25. Give them a call.
The parts to install it all were under $40 from Summit, but Shelby has that stuff, too.

djoneill

Thanks, yes, the answer I'm settling on is try other dealers. I'll just get on the phone and start calling around to the various service departments.

Yes, I was thinking about 3.55 or 3.73, but the granny gear in the v6 MT82 really doesn't warrant steeper gears for my style of driving.

I already have some new take off 3.31s to go into the car, so I'm all set there. I tried to buy them from Shelby, but they've been out of stock for months (all those v6 owners!).

Scotty, thanks again for all your gear info out there-- you're the man with the info as usual!

I was going to buy a tuner to change the ratio, but it looks like you still have to flash the PCM just to change the ratio, which I'm trying to avoid.

Thanks all-- Happy Holidays!

Radioguy

Actually, I think you will find that the Ford Dealers can't flash the 2011+ cars for any gear that wasn't either standard or optional on the VIN of the car. The 2011+ verts did not have 3:31 as a factory option - the coupes did. I had that discussion with my dealer - later heard that new 2011+ECU tools don't allow "non-optional" change to the ECU.

StangisSwag

hmmm, im planning on getting 4.10 or 3.73 on my 2011 coupe, i thought all you had to do was install them and then put the tuner in and select your gear ratio?

djoneill

@Radioguy - thanks, that is interesting. I contacted Ford through their customer service department, and they pretty much confirmed I'm out of luck if I want 3.31 gears and a factory tune:

Hi Dave,

My name is Name Omitted and I am from Ford's Customer Service Division. Let me first thank you for being a loyal Ford customer. I had the opportunity to read your e-mail regarding the modification of the axle ratio with your new 2012 Ford Mustang Convertible. I appreciate the opportunity you are giving us to assist you.

First, let me congratulate you on your recent Ford Mustang purchase. I am sure you will enjoy every feature offered by your superb vehicle.

Ford Motor Company does not recommend changes to our products. Only changes that have been thoroughly tested and approved by Ford Engineering should be considered. Also, modifications to your vehicle could result in its not meeting either Federal Emission Control Standards or any applicable Federal Motor Vehicle Safety Standard.

If you need further assistance with this matter, I invite you to speak with the Parts Manager of your Dealership, as he/she can best address your request. If you need assistance with obtaining your local Dealer's contact information, please visit www.fordowner.com.

We sincerely thank you for taking the time to write to us. Have a great day!

Sincerely,
Name Omitted
Customer Relationship Center
Ford Motor Company

@StangisSwag - yes, a tuner can change the rear axle ratio, but only by loading a custom tune on your PCM, which could void your powertrain warranty (at best, blow your motor at worst).