Speedometer calibration

[Bespinoza66]

One thing I wanted to note was the code for 3.15 gears was still on the BCM with the Steeda 4.10 tune still on it. So it confirms others' answers that a tuner does not change the BCM code. The tuning device I used was an SCT X4 so I can't speak on other devices.

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[Brazos609]

T hug e FRPP ProCal can change gear ratio settings.

 

[Bespinoza66]

T hug e FRPP ProCal can change gear ratio settings.

Does it change the BCM though?

 

[Nagare]

Does it change the BCM though?

No, the people saying stuff like this must have manuals. On a manual, it doesn't matter because you "set" the shift points, with an auto it does because the BCM needs to know the right ratio to properly shift. Without using Forscan or the whipple flare tool, it won't be running 100%.

Tuner can say what they want, but it doesn't work like that on the S550 anymore.

 

[Bespinoza66]

No, the people saying stuff like this must have manuals. On a manual, it doesn't matter because you "set" the shift points, with an auto it does because the BCM needs to know the right ratio to properly shift. Without using Forscan or the whipple flare tool, it won't be running 100%.

Tuner can say what they want, but it doesn't work like that on the S550 anymore.

I don't think it matters on the transmission. The BCM has to be change regardless. It doesn't matter for the 2018s because they have a digital speedometer that self-adjusts from what I've read. I think it changes automatically for the GT 350s as well.

 

[Nagare]

I don't think it matters on the transmission. The BCM has to be change regardless. It doesn't matter for the 2018s because they have a digital speedometer that self-adjusts from what I've read. I think it changes automatically for the GT 350s as well.

I was referring only to the discussion of gear ratio change. Digital speedometer is irrelevant to what needs to be updated on speedometer calibration though, that is just an extra digital display option that the GT350 already had. Anything you had to update on the 15-17 would be the same on the 18.

 

[Bespinoza66]

I was referring only to the discussion of gear ratio change. Digital speedometer is irrelevant to what needs to be updated on speedometer calibration though, that is just an extra digital display option that the GT350 already had. Anything you had to update on the 15-17 would be the same on the 18.

People on the forum have already confirmed you don't need to do it on the 2018.

 

[Xzavior1818]

I assume you're talking '18 and newer.
The speedometer self adjusts.
I went from 3:73 to 4:09 in a manual '18 and within 1/2 mile it was spot on to my uniden r3.

I know this is a old thread, but I need to know if this is true?

 

[Bespinoza66]

I know this is a old thread, but I need to know if this is true?

I would just play it safe and get the Whipple flare device

 

[Xzavior1818]

I would just play it safe and get the Whipple flare device

In my application, I switched tires and they are 0.8 percent off and was just wondering. I'm not super concerned over it as il get a different set next time I get tires but just wanted to see if the speedo adjusts its self on the 2019's

 

[Bespinoza66]

In my application, I switched tires and they are 0.8 percent off and was just wondering. I'm not super concerned over it as il get a different set next time I get tires but just wanted to see if the speedo adjusts its self on the 2019's

I haven't heard a definite answer on that. I bought my flare tool for tire and axle ratio changes, seems to do a much better job than using forscan

 

[JohnVallo]

I'll try once again to clarify this "Speedometer calibration" issue in a logical way, and to clear-up some miss-information.
This should apply to ALL years of the S550

Three basic things come into play when addressing this subject: (Tunes and Tuner issues mentioned later)
1. Rear Gear Ratio change
2. Tire size (circumference) change
3. Transmission (Automatic or Manual)

A. If you change Rear Gear Ratio, it Does Not affect the speedometer reading.
(It's not that the speedometer adjusts or automatically compensates for the gear change, It's just that the speedometer is not affected at all by the gear change)
But, depending on your transmission, a Rear Gear Ratio Change may affect other things.
With a Manual transmission nothing else should be affected.
With an Automatic transmission, shift points and possible limp mode issues may be affected by a Rear Gear Ratio Change.

B. If you change Tire Size (circumference), it Will affect the speedometer reading. (All transmissions)

So, Rear Gear Ratio Change only (with Manual Trans), there should be no other adjustments necessary.

Where is the input that drives/controls the speedometer located?
The ABS rear wheel sensors are what provides the input for the speedometer.
They are located at the rear wheel hubs and measure the revolutions of the rear axle shafts.
Because the sensors are located After the rear-end, and Before the tires, this is the reason Rear Gear Ratio Changes don't affect, but Tire Size does affect the speedometer reading.

So, Rear Gear Ratio Changes (with Automatic Transmission), and Tire Size changes will require some additional adjustments.

In the 2016 S550 the HEX code for the actual Rear Gear Ratio is stored in the vehicles computer memory.
The Axle Ratio Setting is stored in the BCM (Body Control Module) at Location: 726-12-01 XXXX

*This is assuming Ford doesn't change this location in the future*

Thus:
726-12-01 013B = 3.15 Axle Ratio Setting
726-12-01 014B = 3.31 Axle Ratio Setting
726-12-01 0163 = 3.55 Axle Ratio Setting
726-12-01 0175 = 3.73 Axle Ratio Setting
726-12-01 0199 = 4.09 Axle Ratio Setting
726-12-01 019B = 4.11 Axle Ratio Setting
726-12-01 01C8 = 4.56 Axle Ratio Setting
726-12-01 01E8 = 4.88 Axle Ratio Setting

So, I have found that cars with Manual Transmissions, this setting is not used (Has no affect on the speedometer).
Cars with Automatic Transmissions, this setting may need to be changed.
The most common method used to make these changes is with Forscan, other methods for changes may be accomplished with: Tunes, or Whipple Flare Tool, etc.

For cars requiring Tire Size changes here is a Great Thread to explain exactly how to Correct your speedometer for a Tire Size Change.
https://www.mustang6g.com/forums/th...ometer-error-no-flash-or-tune-required.67564/

 

[Saulhcoello]

I'll try once again to clarify this "Speedometer calibration" issue in a logical way, and to clear-up some miss-information.
This should apply to ALL years of the S550

Three basic things come into play when addressing this subject: (Tunes and Tuner issues mentioned later)
1. Rear Gear Ratio change
2. Tire size (circumference) change
3. Transmission (Automatic or Manual)

A. If you change Rear Gear Ratio, it Does Not affect the speedometer reading.
(It's not that the speedometer adjusts or automatically compensates for the gear change, It's just that the speedometer is not affected at all by the gear change)
But, depending on your transmission, a Rear Gear Ratio Change may affect other things.
With a Manual transmission nothing else should be affected.
With an Automatic transmission, shift points and possible limp mode issues may be affected by a Rear Gear Ratio Change.

B. If you change Tire Size (circumference), it Will affect the speedometer reading. (All transmissions)

So, Rear Gear Ratio Change only (with Manual Trans), there should be no other adjustments necessary.

Where is the input that drives/controls the speedometer located?
The ABS rear wheel sensors are what provides the input for the speedometer.
They are located at the rear wheel hubs and measure the revolutions of the rear axle shafts.
Because the sensors are located After the rear-end, and Before the tires, this is the reason Rear Gear Ratio Changes don't affect, but Tire Size does affect the speedometer reading.

So, Rear Gear Ratio Changes (with Automatic Transmission), and Tire Size changes will require some additional adjustments.

In the S550 the HEX code for the actual Rear Gear Ratio is stored in the vehicles computer memory.
The Axle Ratio Setting is stored in the BCM (Body Control Module) at Location: 726-12-01 XXXX
Thus:
726-12-01 013B = 3.15 Axle Ratio Setting
726-12-01 014B = 3.31 Axle Ratio Setting
726-12-01 0163 = 3.55 Axle Ratio Setting
726-12-01 0175 = 3.73 Axle Ratio Setting
726-12-01 0199 = 4.09 Axle Ratio Setting
726-12-01 019B = 4.11 Axle Ratio Setting
726-12-01 01C8 = 4.56 Axle Ratio Setting
726-12-01 01E8 = 4.88 Axle Ratio Setting

So, I have found that cars with Manual Transmissions, this setting is not used (Has no affect on the speedometer).
Cars with Automatic Transmissions, this setting may need to be changed.
The most common method used to make these changes is with Forscan, other methods for changes may be accomplished with: Tunes, or Whipple Flare Tool, etc.

For cars requiring Tire Size changes here is a Great Thread to explain exactly how to Correct your speedometer for a Tire Size Change.
https://www.mustang6g.com/forums/th...ometer-error-no-flash-or-tune-required.67564/

So ive just bought 3.73 gear ratio for my 2016 v6 automatic 3.15, I have never used forscan before.

This is the correct value my car has to have? 726-12-01 0175 = 3.73 Axle Ratio Setting

And do you know where to modify this value in Forscan, where I have to go and all of that?

Thank you!

 

[bnightstar]

In my application, I switched tires and they are 0.8 percent off and was just wondering. I'm not super concerned over it as il get a different set next time I get tires but just wanted to see if the speedo adjusts its self on the 2019's

For tires I guess you need to change the As Build data. I have 2017 and my track tires are 275/35 so I'm changing As Build data with ForScan to match to 275/35 and It works great otherwise my Speedo is off.

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