Originally Posted by milkjuggz

I don't think there's anything wrong with your car.

I have experienced what you describe as downshifting for a split second then automatically upshifting. I was perplexed as to what was happening when I slapped the stick to the left to downshift only to end up in a higher than intended gear.

What was happening was when quickly shifting and letting the shifter rebound under its own spring pressure, the momentum of the shifter was enough to propel it just enough to the right to make an upshift.

Try this again by slapping it and letting it rebound, vs letting the shifter return to the center with your hand.