The quick and simple answer is no, you most likely cannot change the gearing.
Go look up some rebuild videos of automatic transmissions and you'll get it pretty quick.
Since your 626 is FWD, you most likely cannot change the differential either. It was much different back in the day when there were 3-4 size rear ends used over decades. But modern vehicles all have have their own special casings/gears/etc.
EDIT:
Not FWD, but none the less, it shows some of the internal parts that need replacing with the transmission. You would need to find different versions of these components to change the gearing.