I bought a gryphon progamer a little while back, and because i had bigger tires my spedometer was off. Well i thought that i could use the speedometer on the programmer... I figured out the number for my tires to put into the programmer. (305/60/18) This speed was also incorect comparing to my gps. I figured i had made a mistake and inserted the wrong size and didnt worry about it much. But when i recieved my custum tune not long ago it still was not the correct speed. it is off by about 4mph when i am doing 60-70

what could be causing this to be off, i do not think the tire size is wrong. I thought of the gears might be entered wrong, but i am running stock gears. what are stock gears for a 2006 2wd 5.4L v8? is there something else possibly causing it to be off?

thanks for the help in advance
2wdoffroading

 

What is the axle code on your door jamb sticker?

 

Is it 4mph fast or slow?
The factory dash speedometer will always be 2-3 faster than the reading on the Gryphon.

You'll need to confirm with a GPS or use a different method like using mile markers.

 

it is 4mph slower. and i will have to go look for the axle code

 

axle code is H9?

 

i just went and looked it up, the H9 says 3.55 and my programmer was set to 3.73. guess that was the problem with the spedometer

 

probably

 

i tested it today and it is within 1mph, so that fixed it.

thanks for the help