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I haven't rented a car in a while, and those are the only times when I drove cars with automatic transmission. In the past I always saw "1" and "2" on the shifter. If you're going uphill, especially if you're loaded, you needed to shift down yourself.

Nowadays all automatic shifters are a much cleaner "R, N, D, P".

Where did the "1, 2" go? Presumably modern cars are able to detect whether you're going up a ramp and whether you're loaded. Are cars now fitted with weight sensors and incline sensors to determine the appropriate gear?

For the sake of this discussion, let's assume we're on an n-speed (n=6, 7, 8) classical automatic transmission gearbox, not on an (e-)CVT gearbox.

Specifically

Another way to ask the question is this. Suppose you're riding at 40 kph / 25 mph, and the transmission has just switched from second to third. Now you hit a 10% ramp. If you were driving a manual transmission car, you would shift yourself back to second. If you're riding a car with automatic transmission twenty years ago, you'd shift to "2" yourself. Nowadays there is no longer a "2". A modern transmission will figure it out and (hopefully) go down to second gear until the top of the ramp. How does a modern automatic transmission know that you're on a ramp?

Related

Aside

Is any permutation of "R, N, D, P" possible, or is there a standard, just as we can drive a manual transmission box while looking where we're going and without looking at the labels?

Sam7919
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Most automatic transmissions today are electronically controlled. If you look on the dash of any of these vehicles, you'll see where it "tells" you you are either in "D", "N", "R", or "P" describing what "gear" the transmission is in. Most of these vehicles also will allow you to put the shifting selector into a manual mode, and when doing so, will show you which gear the transmission is in while you are shifting it manually. So, bottom line is, "1" and "2" have not gone away. The systems are just showing it to you differently than it had been before.

As far as how does the vehicle know which gear it needs to be in, it takes into account throttle position (load), the speed of the vehicle, and other factors to know which gear the transmission needs to be in to propel the vehicle down the road as the driver demands.

As far as your Aside, without looking at the indicator? To my knowledge there really isn't any other way to know.

Pᴀᴜʟsᴛᴇʀ2
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