Not quite sure exactly of mileage but it calculates @ 8.8 - 9 and I round up a little for the gear difference. Wasn't much better with the 3.55s. RPMs where screaming on the high way@60 mph. maybe some 3.23s or 2.76. Is there a gear in between these? And another ? is did chrysler make a 4 spd OD automatic for the slant?