screwed up transmission?

i noticed lately that when i let the car coast......around 15-20mph the car downshifts (auto transmission). I think there might be something wrong with the way it downshifts......its very agressive. It feels like the whole car just came to a stop with the way it just slows down rapidly. Anyone else experience this .......or is there something wrong with my transmission?

i have the same problem, around 50 km and also 30 km when i don't push the gas it would down shift. i heard it's because when u try to turn a corner and then speed it would pick up a lot quicker that's why the it downshift at that speed.