Auto Trans????? What year???? What trans????
My best guess is you have an E4OD auto? Seen it before, the planetaries munch up causing what you describe. Needs rebuilt badly, will leave you stranded if you continue to drive it.
If you have a C6 or AOD or Manual trans let me know and I'll do some research for you, but sounds like you have and E4OD to me
Ford guy with twin rockcrawling Samurai's [img]/wwwthreads_images/icons/wink.gif[/img]