I own a Peugeot 607 car(automatic transmission). It works perfectly and selects its gears perfectly. But my problem is that, it disengages whenever am in motion. I will have to take d gear to Neutral, off the car (still in motion), I will quickly start the car and push d gear to 'D' and it will engage back. I have changed the transmission fluid and my problem isnt solved. What can i do pls?.