Yeah, there is a speedo gear in your auto/manual transmission under the car that you can change the gearing for depending on your diff. If you get under the car you will see a connector with 2? Wires coming off it, and 1 bolt holding it in.
Take that out, then go to this website:
and then using their calculator work out using the colour of your old one and the speed, what new colour gear you need to get from ford. And remember you need a HIGHER gear then what you currently have. For example if it's 3.08, you will probably need a 3.23 gear from ford, etc etc.