95 Explorer mis-shifting when towing in traffic

My 95 explorer (4.0 V6) is acting wierd when towing in traffic. It acts like it doesn't know what gear to be in. From a stop, it feels like it's in too high of a gear taking off. Then, I need to practically floor the gas to get it to downshift. It feels "tired."

Any ideas.

Do not put transmission in overdrive when towing.. I assume that when not towing your transmission is fine. Otherwise, check your transmission modulator valve.