Automatics "reclutch' by unlocking the torque converter and using the 2 to 1 ratio of the converter on top of selecting a lower ratio from the gearing. Many cases they use the knock sensor on top of the MAP to do this in relation to speed.
When I would use cheap gas in my supercharged tacoma it loved to change gears. When I ran 93 octane with a bottle of 104 on top of it once it got to over drive it stayed there and mashing the throttle just added BOOST.
