Gear changes were more of a game changer with old 3 speed or 4 speed autos, these new 8 speed transmissions have a huge ratio spread, so the exact rear end ratio isn't such a big deal. My old truck had the 3:21, but with the low first gear it felt much more aggressive than i would have thought. The new one has 3:92 gears and it hits harder off the line, how much is gearing and how much is the new calibration and lighter weight is hard to say. My opinion is that it isnt worth the $$ to change it over, it wont drive much different or get much different economy wise.