Speed adjustment

[Scoot5869]

So my Speedo has always read high by 2.5-3mph and I finally got Insite so I went in and went to the speed parameters and noticed that in the axle setting it was listed as 3.42. This truck as 3.55 rear ends as far as I can tell. If I changed that back to 3.55 would that fix my issue?

[Rawze]

This leads to an even bigger question ...

If the rear axle ratio is incorrect in the truck, you need to find out why.

Did someone physically change the rear axles out with a different ratio at some point?. - The data plate on the truck should show the correct rear axle ratio that was in it back when the truck was new.

Or did some complete idiot copy the program from another truck into yours at some point, attempting to delete it or for some other reason, and you just now noticed that some of the data does not match up?. -= Copying programs off one truck to another is a no-no that leads to efficiency losses, incorrect cylinder balancing, etc. even if the hardware is exactly the same. This is because the ecm only does some of this type of stuffs to match itself up with the engine right after a clean, factory program is installed, and does not bother to do it again after that.


-==

and yeah .. setting the rear axle ratio and the tire size adjustment as well is how you make it match up.

[Scoot5869]

Well I can assume the guy that did the previous programming messed with it but I’m not sure. The truck says they are 355 and the look original. Good ol salt has eroded the plates away on the diffs. I thought the tire size was correct but I’ll
Check them again as well. Thanks

[Scoot5869]

This was also my first time poking around in insite so yes I just noticed it