Is the milage stored in the computer or on the gauge...OR both....My truck has been used for 2 yrs and 90k with out the correct speedo in it it read about 12 to 15 off at 85.......So all this time it has been racking up all these miles and the truck really does not have that many on it........After doing the math it should realistically have 76000 or so.....So the question is, do I change the gauge or the computer or both to get it where it needs to be....?

 

So your speedo reads around 100 when you are doing 85, or 70?

 

Correct......when i am going 85, i am actually only going 70 to 75mph......i changed the gear a long time ago and had a programmer but sold it all.....I need to get the correct milage then i will put a programmer back on and fix it once and for all

 

Assuming it's 02 or older it's in the cluster.