My truck has 4.56 gears, 35x12.50r20 Toyo M/Ts, etc.

No matter what tire diameter setting i change my custom 93 performance tune to, the speedometer will not change.

For example, i had the gear ratio set at 4.56, tire diameter to 2690. When my speedo said 75 MPH, my GPS consistently said 73.3 MPH.

So then i changed my tire diameter to 2670, gear ratio to 4.56. Same exact thing, Speedo sonsistently reads quicker.

I changed it higher, lower, etc etc, can't get it to read differently.

Any suggestions?

 

I'd advise you leave it right there. That's the built in tolerance.

 

X2
The dash speedometer will always read 1-3 mph higher than the speedometer on the Gryphon.
Using a GPS will also help confirm your numbers......

 

Assuming the Gryphon sets like the Edge and in case you are making the mistake I made, after setting the tire and gear specs make sure you scroll up and click "enter" on the list of parameters.

 

The difference you are experiencing is the Ford built in difference, as mentioned above. Use the digital speedo on the Gryphon and match it to the GPS.

 

I know Ford has the computer programmed for the speedo to be slightly faster, but that still does not explain why it wont ever change no matter how much i adjust the tire diameter. I'm stumped..

 

Could you be going back to the screen for the tire setting? If you go back, it reverts to the default. You enter your number and save and dont return to it unlass you select the Save Prior Settings.

 

try using your digital speedometer. you should have one. i thikn the 04+ style has this in it.
while your truck is off hold in your trip odometer button.
turn key to ON but do not start the truck.
after about 5 seconds your odometer should say "test"
let go of the trip button and press it as many times as it takes until it says "speed E" (there will be speed E for english and speed M for metric) then start your truck. your odometer is now a speedometer. it SHOULD be the same as what your programmer.
FYI your truck will still count the miles added on. when you shut the truck off it will go back to the default setting next time which would be your odometer. you CANNOT see your miles again until you shut the truck off and start it again or turn it to on again(so the next time you turn your key after you shut it off it will go back to normal)there are a bunch of things on there to toggle thru, maybe close to 40 but i think the speedometer is about 15 or so into it. there is also a tachometer. this will work in ANY ford truck/suv that has a digital odometer with a trip button. older vehicles will not have all of the same stuff but i know for sure the tachometer is on new and old. speedometer was not on my 04 heritage but should be in 04 NBS.
i did it with my 08 and my analog was 1-2mph off from the digital depending on how fast i was going. but i checked it with a construction zone radar and the digital speedo was dead on. hope this helps

 

thats pretty cool i might have to try this for kicks

 

i made a video a few months back
http://video.cardomain.com/VideoPlayer.aspx?id=743514

 

The two numbers you used in your first post: 2670 and 2690, differ by only 0.75% (less than 1%). This, at 73.0 mph is a difference of only 0.5 mph. I doubt seriously you will see this difference on an analog dash speedometer. The dash at 75 and the GPS at 73.3 sounds VERY close. Possibly, you should INCREASE the TS to 2710 to make your dash speedo read about 2 mph high if you want to be "dead accurate" on the odometer, but that's about all I'd do.

(I would have started with 2709mm, which is your tire size with a 3% squish factor.)

- Jack

 

I'm having the same trouble with my SCT X3, only mine is aprox~10KPH to slow compared with my GPS.

Jason sent me a new tune to no avail, and asked me to contact the manufacture direct. since no mater what ratio I enter, no difference is seen on the speedo.

Haven't had time to contact them......but if anyone has other info feel free to share.

 

On an X3 you should be able to adjust both your Tire Size and Rear Axle Ratio (Gear Ratio). I think the X3 uses Revs per Mile for Tire Size (TS) instead of tire circumference or diameter and I don't know how the Gear Ratio (GR) is entered, but probably as a number like "3.73".

From what you are saying, your TS/GR combination is way too low, possibly by about 17%. You would get your GR from the VIN sticker on the door (provided your truck still has the OEM gears), and it's possible you have been giving Justin a figure that is incorrect. What tires do you have on your truck?

- Jack

 

Sorry, did not mention that everything is set properly. Gear ratio set to 3:55, rev's per mile set accordingly to tire manufacturers spec etc. But no matter what changes I make in the tuner makes a difference, even the new tune with the settings input from Jason did not work. Jason thinks it may be the hardware in the tuner itself.....Just had too much on the go to contact them yet.

 

Thanks for the reply, i'll try that.