haha how did pixy magically know you're driving spectra?
i believe for spectra, there're only 4 gears in the auto
transmission. the over-drive as referred by you COULD BE meant by
"over-drive OFF" which means that when you activate it, your
transmission will reach 3rd gear at most.
auto transmissions which have more than 4 include the honda odyssey
which have 5, and the lexus ls430 with 6.
yes the auto transmission takes care of the fuss since you've paid
the extra few grand for the AUTO. going upslope, it will downshift
to gain extra push if your car is losing the torque. however, in
cases when it's not responsive enough, you may step on the gas
further to signal for the extra push, or use the over-drive off
function, or manually shift the auto gear-stick to the lower
numbers.
going downslope, haha, that's why auto cars tend to eat brake pads
more. however for long downward distances, again, that's what the
smaller numbers below the D come into good use to spare those brake
pads.