Solnoid pac
Inside your tranny is a solinoid (sp?) pac, this controls 1st & 2nd ( drum/clutch controls the OD (at least I understand it does) Since you've overheated because it wasn't shifting the bands to break down and will eventully gum up the tranny with a sand like material. However you may also want to pin out the harness to ensure you haven't got a broken wire (mine had a break in it (but wasn't noticable until we pinned out the connector. I'd check the harness 1st (least expensive option) then check the pac before dropping the tranny out, BTW iyou'll know if the bands have broken down as the material will show up in the tranny pan.
Good luck, been there & done that! but mine was under warrenty thank god!