I've a 2001 Ford Explorer, 128k miles, purchases as a donor for a restomod project. The Explorer's transmission metal label attached says AODE. However, the electrical connector is black revealing the transmission is a 4R70W. and using an aftermarket controller and wiring harness we confirmed the 4R70W type. The tranny worked in few test drives.
I pulled the pan to replace a seeping pan gasket and found the attached floating freely in the pan full of fluid.
Surprized to find this, I don't know what it is. Does anyone have any ideas what it could be for?

Mystery part

It's plastic, with a rubber o-ring, about 1.5" long.

 

It goes where the dipstick hole is. Just gets pushed into pan when the tube is installed

 

Thank you....i found that on a youtube as well. ATF never been changed.
Thank you.