Need help guys. I had my gears changed from 3.55 to 4.10's. My speedo is now 8 mph out. I went to ford to have the computor adjusted. My computor only goes up to 3.73. So we changed it to that. My speedo is still about 8mph out. Ford is telling me I need to get a chip to add the 4.10 gear change???? Is this correct and how and where can I do this. I am not sure where I can buy this so called chip. P.S we also tryed to alter the tire size in the computor to trick it thinking it would bring the speedo back down. It did not work as well.

 

buy an x-cal.