Originally Posted by macho_mike21
FWD is the most efficient setup isnt it? (Since the power doesnt have to change directions?)
Changing directions doesn't play as much a role in the efficiency as does the design of the transmission in the first place. The aforementioned Chrysler transmissions are longitudinally mounted and extend backward just as a RWD transmission would. They then have a gear set and chain that transmits the power back forward to a standard differential between the engine and the transmission (albeit part of the transmission housing). This design coupled with the weakness of the internals inside this transmission make for a highly inefficient transmission.
Automatics will always be less efficient than a manual gearbox because automatics have to use some of the engine power to run the pump in the transmission. How much of a difference depends on the design of the transmission. You will never have an conventional automatic match the efficiency of a manual gearbox because of the pumping losses.