My truck's driveline/gearing is stock, but has taller tires. I did the wizard thing back when I first started messing with it and assumed all was good, as after the adjustment the speedo matched my GPS. But recently I noticed in a log where I had cruse set at 55, scanner's MPH was a steady 58. Went back and reviewed my dashcam's GPS and it's still agreeing with the 55 number.
Stock gear is supposed to be 3.73, stock tire per the placard is 245/60-18 (29.6"). Current tire is 265/60-18 (30.5"). I don't have a clue why it looks like the stock tune is set up for a 30.93" tire & 4.10 gear (that's what the wizard shows in the stock tune), as that's not what the truck left the factory with. I put the stock tune in there myself via TIS2000 using the actual VIN, I don't know how this doesn't match or if it really matters.
Screenshot of speedo tab before(top)/after the wizard changes:
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