issue with speedometer calibration

[Chief of Booty]

i received my i3 today in the mail and have let it fully update. the issue im running into is when i try to change the gear ratio for my car (2002 pontiac ws6 transam) from stock (3.42) to its current gear (4.10) the speedometer is reading massively below what it should be, when im going 75 mph the speedometer is reading around 35 mph. when i go back to the stock tune or the 91 tune (without the gear change) the speedometer goes back to close to what it should be but is still off because its set for the wrong gear. the issue comes up the second i try to change the gearing which causes the speedometer to barely move. i have also tried the advance tune by adjusting the parameters for both the gearing and the tires but it does the exact same thing. the only thing i could think of that could cause my issue is the i3 thinks my car is an automatic causing the speedometer to be locked to what would be the automatics 1st gear rather than whatever the current gear is with my manual.

[Royd111]

mine read 4.5 miles off after changing tire size and putting the new tire size in the tuner. I read on another forum to put in tire height. I used a tire size calculator and figured out what size height to use (more than an inch shorter than actual size). Anyways I put in different sizes until I found one that matched how far off my speedo was. You may be able to do something similar. I used a GPS app on my phone to find out exactly how far off I was.

[Chief of Booty]

The gear i have currently in my car is a 4.10 and the tires are stock at 275/40/17 or 25.66" in height. when i try to change the gear from its stock ratio of 3.42 to the new one (4.10) the speedometer says its reading 35 mph at a GPS verified speed of 75 mph on the highway. using the diablo tune (91 octane) itself does not affect the speedometer reading but the second i touch the gear ratio settings the speedometer becomes completely off. using advanced tune and adjusting the gear ratio and tire size in the parameters just causes the exact same results.

[Royd111]

I know it sounds messed up but with the 4.10 gear ratio in the tuner try also adding a 53.4" tall tire and check your speedo again.
Something is now right to have to it off that far

[Dave_928]

When calibrating the speedometer, what is the preferred method to use? Tire height, tire size or both?

I only ask because my son added larger wheels and tires to his truck. When he tuned it, he added the speedometer calibration, but only put in the tire size.

[Royd111]

for me tire size and tire height both led to speedo being off. Mine was off 4 miles an hour @ 60 using a GPS speedo app from Google Play store. So I went to tiresize.com/calculator/ and put in my tire size then tried different sizes until I found one that was 4 miles off @ 60 mph. Then I inputed that tire size height into my tuner and rechecked speedo. Now my speedo is dead on

[Dave_928]

Very interesting. Thank you, sir!

[Chief of Booty]

So I've tried multiple gear ratios at this point like 3.73, 3.55, 3.42 and they all do nothing to fix my issue and is pulling the exact same crap of registering far less than it should on my speedometer. It seems the second I try to input any custom value into the tuner it defaults to a low reading whether it's a custom tire size or gear ratio.

[mikel]

So I've tried multiple gear ratios at this point like 3.73, 3.55, 3.42 and they all do nothing to fix my issue and is pulling the exact same crap of registering far less than it should on my speedometer. It seems the second I try to input any custom value into the tuner it defaults to a low reading whether it's a custom tire size or gear ratio.

can you load the tune with no axle ratio changes then post the backup and last tune written files from the tunes folder here so I can fix this for you?

[Chief of Booty]

okay i retuned it without the gear change and i believe these are the files you were mentioning

[Chief of Booty]

?????

[mikel]

Sorry, calibrator has been on vacation, will get this as soon as hes back.

[Chief of Booty]

Ok

[mikel]

here you go.

[Chief of Booty]

ok i got it loaded into my car and the speedometer is still doing what it did before when i tried changing the gears with the device. its reading 10 mph when im going 30 mph and 35 mph when im going 75 mph. this is getting frustrating and im not seeing any improvements.