Either way, it is an adjustment of the factory settings on the ECM, which in turn = loss of powertrain warranty in most cases (ask you local dealership to be sure).

I had my gears swapped on my 12' 5.0 with the speedo calibrated at the dealer and no effect on warranty. If I calibrated on my own using an SCT tuner for example, they may have had an issue with that since it involved a reflash.
I don't see how calibrating your a speedo would have an effect on your powertrain especially with a device specifically designed to calibrate the speedo only.

Like I said, go talk to your local dealership, there are a few that are more lenient than others on this subject. Maybe Ford had a different policy? I just know I've heard it on here many, many times....ANY change to the factory settings on the ECM is an automatic void of the powertrain warranty in most cases. Call up your service manager at your dealership......and let us know what he says.

I hear you and will look into it with my dealer but nothing automatically voids your whole warranty just like that.

I had a stock Formula in 1987, with a rare 3.73 gear option from the factory with a 350 tuned port injection and the car was freaky fast for the era. Rear end gears help a LOT. I would love to get another 3.73 with my 5th gen. It would make a difference.

DANHR
THANKS FOR THE INFO FROM U AND EVERY ONE
SPOOKYGUNNER

Now that the 1LE has the 3:91 gears, I can't see why the dealer can't install then, while still maintaining the powertrain warranty, but then again like most have said I guess it depends on the dealer, but it's worth a shot.

You would think so and probably only for the manual and not auto since the 1LE only comes in manual :iono:
I had 3.73's installed in my 12 5.0 ( a factory option)and the dealer was cool about the overall powertrain warranty but if I had any issues with my rear end it would be on my dime...
Also make sure to find someone that knows what they're doing with gear installs. Ive had it done by so call experience professionals (one a dealer)and both times they made noise loud enough to hear over the radio.:mad0259:

Many thanks to danhr for this thread. I have a couple of questions as a result of all this good info.

1. So... the stock/factory gears in my 2013 SS L99 Coupe are 3.27s?
2a. Assuming the answer to #1 is yes, if I want "quicker" 1/4 miles times I should go to 3.47s or 3.73s?
2b. Which gears are optimal for increased times with excellent reliability?
3. For highway cruising (I take frequent trips), how will the higher gears (3.47s or 3.73s) affect MPGs, road noise, etc.

Thanks for any input.

i went from 3.27 to 3.73 and saw appx 250rpm difference going 70

If u have the traction 3.73 will. Help u getting out the hole a lot

i run 4.10s which make my gearing about the same auto with 3.73.. fine daily driving. I do 25k a year. MPG went down like 1 or 2.. considering these cars have wide gears its fine

I'm looking for the torque spec for the rearend end caps and back lash

wow .... I'm all confused :frusty:

I already have a supercharger and a stall convertor .... would I see or feel anything by changing the gears on My A6 SS? Was going to try and get the 3.91's but now they are on back order and from this It sounds like I'm wasting my money with the whipple and stall already there:doh:

Wow man I forgot about that song, Bitchin Camaro, by the dead milkmen, remember hearing that for the first time back in the 80's when a buddy of mine with an 86 Mustang GT, brought a cassette into my car which was an 87 Formula 350, he said you have to hear this song by the DEAD MILKMEN, I thought it was a very cool song,
and was the last thing I expected to hear from a punk band like that! Thanks for posting it, brings back cool memories!