Ihave a 99 Windstar that when it warms up the transmittion warning comes on and o/d light. It then slightly slips when slowed down. Runs fine when cool. Any answers?

First thing you need to do before anyone can give you much of an answer is find out what the trouble codes are. If the OD light is blinking, then it means that the transmission controller is reporting trouble codes. Get those codes and go from there.

Something else you can do is check the fluid level. If it's low, top it off and see how it behaves.

When you get codes, you can also check what they mean if you download the service manual from here:

http://www.fordcds.com/

Download the ISO for 99 Ford trucks.