axle gear tag vs. tune ratio

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09-12-2016
joepeek

axle gear tag vs. tune ratio

This is not really what I would call a difficult tuning question, but wondered if anyone can explain it. I have a 2005 Mustang GT, bought it new. On the differential cover there is a small sticker that says 3.55. In the Speedo section of my tune it shows the rear end gear as 3.55. My son just got a 2007 Mustang GT (he liked mine so much he got one just like it, now we have some great father/son car time). Anyway, the differential cover on his 2007 GT has a 3.55 sticker on it as well, but when you look at the Speedo section of the tune file, it shows 3.31? 3.55 & 3.31 were the two available ratios. I will check speedometer accuracy to verify, but was wondering why the "mis-match", and would it effect anything other than speedometer accuracy if I changed his tune to say 3.55, if in fact his speedometer is off calibration. Just seems odd to me...........maybe just a factory mistake?
09-12-2016
Eric@HPTuners

Quote:

Originally Posted by joepeek

This is not really what I would call a difficult tuning question, but wondered if anyone can explain it. I have a 2005 Mustang GT, bought it new. On the differential cover there is a small sticker that says 3.55. In the Speedo section of my tune it shows the rear end gear as 3.55. My son just got a 2007 Mustang GT (he liked mine so much he got one just like it, now we have some great father/son car time). Anyway, the differential cover on his 2007 GT has a 3.55 sticker on it as well, but when you look at the Speedo section of the tune file, it shows 3.31? 3.55 & 3.31 were the two available ratios. I will check speedometer accuracy to verify, but was wondering why the "mis-match", and would it effect anything other than speedometer accuracy if I changed his tune to say 3.55, if in fact his speedometer is off calibration. Just seems odd to me...........maybe just a factory mistake?

There are two ways for the PCM to know the axle ratio. It is stored in the VID block, with other information like the VIN number and some other oddball things, and it is also in the calibration. There is a switch we have defined that determines which value it uses.
09-12-2016
Jn2

Like Eric said, if you have "Use VID block: enabled then don't worry about what the tune says. You can fix it, it won't affect anything thought.

I have a Track pack 13' with 3.73 and the tune said 3.31 but I'm using the VID block so it doesn't affect speedo at all bc the correct ratio is being used. I did however update it in the tune anyway for redundancy.
09-12-2016
joepeek

Axle gear tag vs. tune ratio

Quote:

Originally Posted by Eric@HPTuners

There are two ways for the PCM to know the axle ratio. It is stored in the VID block, with other information like the VIN number and some other oddball things, and it is also in the calibration. There is a switch we have defined that determines which value it uses.

Thanks for the info guys...........I clicked around in the editor, but can't seem to find the VID block to see what it shows for gear ratio.

I found where the "use VID block" info is ENABLED in the Speedo section.

Just can't figure out how to see the content of the VID block?
09-12-2016
AKDMB

I might be misunderstanding this, but I think that if the "Use VID " switch is turned to "Enabled" then the car uses the data that's already in the VID Block. Flipping the Switch to "Disabled" means that the car will use the data that you changed in the "Speedometer Calibration" section of the VCM Editor. So if the car is on the stock tune, and the "Use VID" switch if set to "Enabled", don't worry about the values you see...Is this Correct?
09-13-2016
Jn2

Quote:

Originally Posted by AKDMB

I might be misunderstanding this, but I think that if the "Use VID " switch is turned to "Enabled" then the car uses the data that's already in the VID Block. Flipping the Switch to "Disabled" means that the car will use the data that you changed in the "Speedometer Calibration" section of the VCM Editor. So if the car is on the stock tune, and the "Use VID" switch if set to "Enabled", don't worry about the values you see...Is this Correct?

Yes,

Enabled = Use VID block(stock tire height, no changes to speedometer)
Disabled = Use what ever you wrote in your tune(use this when you change tire size, just be sure your diff ratio correct if you do disable it)
09-13-2016
joepeek

Axle gear tag vs. tune ratio

Quote:

Originally Posted by Jn2

Yes,

Enabled = Use VID block(stock tire height, no changes to speedometer)
Disabled = Use what ever you wrote in your tune(use this when you change tire size, just be sure your diff ratio correct if you do disable it)

Very excellent info, if I change tire height or gear, I'll just disable the VID and type in what I have straight up in the Speedo section of the tune. But, I still don't know how to see what is in the VID file. Even if it is just to see what the stock info is. How do you read the VID file info?