I was looking at transmission specs on GM's web site and noticed that the Aisin 5 speed automatics used in the Chevy Equinox/Pontiac Torrent and the Saab 9-3 and 9-5 don't have an overdrive gear. They make up for it with a very low first gear (approx 4.7/1) and high axle ratio (approx 2.5/1). GM's 5 speed autos, however, use one overdrive gear and the 6 speeds have two with the typical axle ratios (3.05, 3.29, etc). What are the advantages either way? I'm curious about Aisin's reason for not including an overdrive gear.