Let me preface this question with the fact that I know how automatic and manual transmission are different in their operation. My question is, however, why do they differ in their amount of gears and subsequently their gear ratios? I can understand the difference in ratios when the two have a different amount of gears which seems to be almost always. Even in a performance car like the Porsche 911 Carrera the manual is a six speed while the automatic/tiptronic (full manual capable) is a five speed. This is just something I've been pondering for a while and I'm sure there is a simple answer but I have been unable to find it.