Typical mount that might mess up is the one on the front of the trans. It'* the equivelent of a marshmellow, not good for much but lighting on fire..
Your symptoms are familiar though. If you had the codes read w/o shutting it off when it was slamming, most likely you'll find the Max Shift Adapt code. It'* something like P1811 (not that I know it off the top of my head
). When the trans sees something it doesn't like or the common pressure control soleniod starts heading south, this can happen.
Not that long ago someone posted about installing a shift kit and a can of seafoam trans tune. A few others followed along seeing good results. Personally it'* a bandaid, but the pcs is deep enough inside that the side cover on the trans has to come off which means trans has to come out.