my old 89 did exactly that a few years ago... immediately following a good engine soaking.. would also only down shift when it was put to the floor... sometimes. TPS was my culprit..
mike
i traced it down to the trans controller thats hidden below the glove box...the terminals were loose!!...i disconnected the batt and pulled off the plug and squeezed the terminals tighter...peinstalled and viola!!!....it works perfectly!!!...i'm a mechanic here at the local dodge dealership and thats how i found out about the controller....lol.. :cheers: