automatic with stock 3:55s?

06TORCHEDGT

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I recently had my tune updated for my JLT cold air and was driving on the the interstate yesterday and noticed my speedometer seemed off. So I got the gps out and it confirmed it was off by around 4 or 5 mph, went home and put the tuner on the car and checked it out to make sure it was tuned for 3:31s so I reloaded to tune for 3:31s and took it down the road with the gps and was still off, then I reloaded the tune for 3:55s drove it again and the speedometer is dead on the mph. So was there away the car was ordered with 3:55s from the factory? Car was bone stock when I bought it.
 

eddieval5

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Check for a small rectangle like sticker on your rear end cover. Mines an auto with 3.31s *sigh*
 

bmaxwell

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2006 didn't come with 3.31 I am pretty sure that was 07 and up
 

bmaxwell

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Oh well then apparently my sources are equal to that of shit and piss! Both of my 06s had the 3.55s so it seemed logical lol. The first was the premium so I can see that but the second was a complete base model so I didn't think it had any upgrades like that
 

06TORCHEDGT

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Check for a small rectangle like sticker on your rear end cover. Mines an auto with 3.31s *sigh*

Didnt know that so ill check tomorrow, but I guess itd have to have 3.55s for it to be tuned to 3.55s and have the speedometer read correct lol. Was the 3.55s a factory upgrade for the autos kinda like you can upgrade the 2011s to 3.73s?
 

JeremyH

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In 05/ part of 06 all autos got 3.31s and manuals got 3.55s. The mid 06 into 07 they all got 3.31s. All the while 3.55s were a factory option. My 07 came with 3.55s and they are listed on the window sticker.

Op you can look up your window sticker online with your vin or you can check the build code sticker inside the door jam to confirm the gears you have.

Also its not uncommon for veloctiy in a gps unit to to read 2-4mph off from a cars speedo btw.
 

maco7173

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Was this just on the Autos??? I have a 2006 with Manual transmission and was told that all manuals came with 3.55s.
 

RedfireV8

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Didnt know that so ill check tomorrow, but I guess itd have to have 3.55s for it to be tuned to 3.55s and have the speedometer read correct lol. Was the 3.55s a factory upgrade for the autos kinda like you can upgrade the 2011s to 3.73s?

Yes, option in 06

In 05/ part of 06 all autos got 3.31s and manuals got 3.55s. The mid 06 into 07 they all got 3.31s. All the while 3.55s were a factory option. My 07 came with 3.55s and they are listed on the window sticker.

Op you can look up your window sticker online with your vin or you can check the build code sticker inside the door jam to confirm the gears you have.

Also its not uncommon for veloctiy in a gps unit to to read 2-4mph off from a cars speedo btw.

I just want to make sure no one missed it but the OP has an AUTO. I was always under the assumption that all 05-10 Auto Mustangs had 3.31's. Is this not correct?
 

Five Oh Brian

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I recently had my tune updated for my JLT cold air and was driving on the the interstate yesterday and noticed my speedometer seemed off. So I got the gps out and it confirmed it was off by around 4 or 5 mph, went home and put the tuner on the car and checked it out to make sure it was tuned for 3:31s so I reloaded to tune for 3:31s and took it down the road with the gps and was still off, then I reloaded the tune for 3:55s drove it again and the speedometer is dead on the mph. So was there away the car was ordered with 3:55s from the factory? Car was bone stock when I bought it.

All '06 to '10 GT Automatics came from the factory with 3.31's. No factory option for any other gearing in the automatics.

Are the tires OEM, or is it possible that you bought the car with lower profile tires? That would explain the speedometer being off.
 

Sinner

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i had the same issue with my auto. the door jam and rear diff cover both were marked as 3.31s but my speedo was off so when the car was tuned the setting was changed as 3.55 gears and the speedo was dead on. so, i'm guessing someone changed the gears to 3.55s at somepoint but it seems like a waste of money to make that small of change.
 

06TORCHEDGT

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Well I checked the door jam and diff cover and they both say 3.31 on them, I never had an issue with this until I got this new tune for the jlt. so im getting the tunes redone now, im thinking there is an issue with the tunes so hopefully this will be resolved with the new tunes.
 

Shaffe

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Im pretty sure that in the auto cars you can NOT order a different gear. but I could be wrong, I think all cars with the 5R55S came with 3.31
 

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