Taking car to dealer and leaving overnight. Car is 2009 3.3 with 81,000 miles, Trans replaced at 57,000 miles by Hyundai. So what is happening now is when it is cold in the mornings my trans slips from 2nd to third, RPMS rise followed by loss of power then it goes into gear. I then flip to manual and see it is in 3'rd to try to rule out a stack shift. I have a slight incline near my home it seems to happen on that not on the flat going to the hill. After 2 or 3 shifts it is fine with no issues til it sits again for a while. I am original owner so I am still under powertrain warranty. Anyone hear of what I am describing, I hope it is not a bad valve in the trans. Every time the dealer tried to check it, it is fine, so I will leave overnight. I am not sure but I think it tends to happen when defroster is on.