Originally Posted by Northland
Are you sure you didn't hit one of the paddle shifters by accident, thus putting the transmission in manual shift mode?
I've had the same thing happen with a V8 '14.
Dunno what causes it but if you hit the gas hard, then almost immediately let off, it seems to downshift and then hold the lower gear longer than normal.
It will upshift after a bit, or you can just pull on the + paddle for about a minute.
Acts very similar to changing to sport mode when I do this.