I have a 2007 Sport Trac Limited ( 6 speed Trans ), The O/D light stopped working, But Trans seems ok, Could this be just a burnt out bulb?

 

When you press the "O/D Off" button does the transmission seem to not be allowing overdrive? If not, then there's a pretty good chance the issue is with the wiring for the O/D Off switch. That was somewhat common on older Explorers. I'm not sure if the O/D Off switch is still on the shift lever on your 2007 or not.

A professional scan tool may have the ability to turn on the O/D Off light from the tool to confirm whether or not the bulb is working properly. It would also allow you to confirm whether or not the switch is working.

-Rod