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I have an 03 hemi 2500 with nitto grappler's 325/60/18 approx. 33 1/2 inches the speedo is off by like 4 mph any ideas on calibraters I know of super lifts systems and they will not work for the 03 5.7 ltr..but then to I do not have a wiring diagram for it either it is different than the 02 ..can anyone help?

I not quite sure what you are saying but speedo calibration is done by the wheel revolution per mile I believe it was scott's statement on another question.This done by calling your tire manufacture and asking the wheel revolution per mile at a given speed.Then your dealership will plugin and dial that revolution per mile into the PCM software on board.This will correct many things as far as trans shift,kickdown,fuel mileage,shift points.You may what the tech to drive with you to see if you like what he is seeing with the hand held programmer.And what you are feeling as far as excelleration and shift points.Also if that truck was factory equipt with 265/70/17 then you might be more off than you think with fuel mileage and shift points and speedo indication.Good Luck