My gps on the nav system just recently started showing me no where near where I am. Whether I'm on a planned route or just looking at it normal. The little arrow is either two or more blocks off or all over the place. It was working fine but now goin haywire. Visited a ford sync guy and was told that any tire size over factory will mess it up. Well, I have had the same sized aftermarket tires on it since I put them on shortly after buying. There are dealers that put lifts and over sized tires on the trucks then sell them on show room floor. After talking to those dealers, they haven't had any complaints. Anyone else having this prob and if so, has anyone figured out a fix