sorry to say this but depending on which gears are in it, which gears came from factory, which tires are on it and all tires it has had on it, and what speedometer gear it has now that is you looking at me and guessing how many kids I have...you might be right...but need more info probably info not readily available with out asking questions of PO and KNOWING what has been done to it when.
I KNOW my mileage on my '04 TJ is "off" because I ran 31"s for 7 years without changing anything from the factory and it came on 29"s. In addition to that I went to 33"s and drove for 2 years before I regeared. After I regeared I FINALLY changed the speedometer gear to match gears in the tranny, and tires. I know it is off but the question is how much?
All you need to do is post up the mileage where you changed tire size. And if you changed gears post that up too, also helps to know what transmission you have. You can figure it out with an online calculator, but that's only assuming your tires are an exact measurement. Post up the size of the tires as stated on the side walls (before and after). Your dealer can alter your odometer, but why would you want that? Your bigger tires are feeding you a lower reading, but with any of the above info you can fix the problem of the speedo being off.
Jeeps never get stuck or broke. Just parked in odd places for an indeterminate length of time.