94 f150 4x4 which transmission?

I've got a 94 f150 4x4 that has begun to do a lot of loud grinding when idling in park or neutral (sound goes away when I put it in gear). It' an automatic with overdrive, overdrive off button is in the end of gearshift. how do I tell what transmission I have, so I can start looking for one? thanks

E4OD transmission. You may have to stay in certain years so the computer works right.

Does the noise go away when you drive it? Does the transmission otherwise work okay? Have you tried diagnosing the problem? It may be something simple.

Thanks for the info. the last time I drove it it didn't want to move in reverse, after shifting into drive then into reverse it did, and the occasional same grinding noise. Other than that, it shifted and moved ok.