trasmission overdrive on 2003 Mercury Mountaineer

the transmission overdrive just stop working,the fuild is full. It has 68470 miles and never had a problem until now.
Checked all overdrive fuses. Is there a relay that I missed.

Asked by for the 2003 Mercury Mountaineer
2003 Mountaineer do not have dip sticks you can not check transmission fluids. It is a close pressurize system. You will need a professional to check for problems.