In the automatic I’m nervous about the unfamiliar kickdown feature, and when I drive hers I use the paddles more often than she does, either to pass on a two-lane road or to force a downshift on a hill or the like.
Kicking down is really easy when it is a request for increased power: just put your foot down and hold it there. But the transmission has to be maintained in order for kickdown to be consistently smooth.
When the transmission kicks down, there should be a brief pause (often the PCM is configured to retard ignition timing to ease the torque transfer across different wet clutch combinations), then an increase in engine buzz as the engine spins up to the higher RPM, and a gentle "springing forward" sensation of increased acceleration as the driveline winds up and the added power starts reaching the wheels. If the fluid is old and thin, as happens when the transmission is not maintained properly, there is often a slam as the gears change, which has the effect of frightening drivers.
I’m more comfortable controlling the downshift than I am letting the car do it, and on hills I’ve found many automatics try to hold too high a gear and I suspect this is why many drivers slow down too much going up anything more than a minor gradient.
My suspicion, as someone who has climbed hills using an automatic, is that most drivers try foot-feeding their way up hills and react far too late to avoid speed drops once their vehicles bite into grades. To avoid significant speed drop, you almost have to start accelerating for the hill
before you reach it.
For mild to moderate grades, solenoid-actuated cruise control is generally better at responding promptly to speed drops as the car starts ascending. In my Saturn, which has working cruise control with TranSynd in the transmission sump, I can set the cruise control for 65 at the bottom of I-70 just west of Denver, move into the far left-hand lane, and pass everyone else on cruise control all the way up the grade (about 6%). The transmission just bounces from 4th to 3rd and back again (shifting smoothly each time) as required to correct small speed drops.
The Saturn is 1990's tech. 2000's tech includes hill detection logic, which can hold speed within even tighter limits and, to an extent, control speed on downgrades without driver intervention. The hill detection logic on my 2005 Camry works so well that when I go over the Fred Hartman Bridge in Houston, I move to the far left-hand lane, passing everyone else that slows down for the climb to the top of the navigational envelope, and then move to the far right-hand lane, being passed by everyone else, with cruise control maintaining set speed of 60 throughout.
Bottom line: most drivers don't have reflexes good enough, or pay close enough attention, to outperform control logic when attempting to hold a steady speed through changes in vertical alignment.
P.S. I suspect many drivers may have a preference for trying to foot-feed their way up grades that was learned during the 1980's, when vacuum-actuated cruise control was state of the art. With vacuum actuation it does make sense to change over to foot-feeding because it is almost impossible to make the vacuum diaphragm big enough to pull hard enough on the throttle cable when the engine is under heavy load and intake vacuum is minimal. This is especially true at high altitudes (e.g., I-70 over Vail Summit), because ambient air pressure is so much closer to manifold absolute pressure to begin with.
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