I live in an area that has lots of topography and so whenever i'm on the highway I find that i'm constantly shifting betweed "Drive" and "Overdrive". The automatic transmission does not want to downshift to
3rd gear on it's own and I can feel it as I start heading uphill more and I give it a little more gas the car does not maintain it's speed very well and it still doesn't want to downshift. This happens about 100 times on a 1 way highway trip for 215 miles. Whenever this happens I'm faced with option: A) Shift out of "overdrive" and into regular "drive" or B) "Kickdown" done by nearly flooring the gas pedal in order to get the stupid auto transmission to downshift into 3rd gear. (seems to me this option is hard on the whole drivetrain)90 percent of the time I do option (A) because I don't want to waste gas or increase my speed. I'm usually at the speed limit and so it's better to shift out of overdrive so I can maintain the same speed without it being hard on the transmission or the engine. And without revving the engine way up higher than it needs to be.
It seems to me that if I don't shift out of overdrive it's probably putting unecessary additional strain on the combustion chamber and the transmission. This is probably why many cars blow their head gaskets because there's too much of this strain-pressure on them when the transmission refuses to downshift when it should.
Does shifting on the fly - from Overdrive to Drive and back and forth constantly -- does this wear out the transmission substatialy over time? Or is it just normal wear and tear and the transmission was designed to be operated in such a way?
This is exactly why I miss driving a car with a manual transmission. The "autostick" on newer cars these days has got to be well overhyped compared to simply being able to master a car with a standard 5 speed. Why make things more complicated than they have to be?
How do most people drive this sort of car on mountain/hilly terrain? Just keep in in overdrive and ride the brakes the whole time? (I learned to drive using a 5 speed and so I really prefer not to ride the brakes and to instead downshift, and use engine braking.)
TIA!!!