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Depends on the car, and how many planetary gearsets it has. A Neon is a 3speed, 1-3-od is what is on the shifter, it shifts to second at 20mph, between 24-35 it shifts to third, overdrive engages around 40. Axle/transaxle ratio has something to do with it too, i think, my dads ranger shifts faster than my mamas neon sxt.
You've just described a 4 speed. OD still counts as a gear.
Most n-speed trans have n-1 drive gears and 1 overdrive gear. Still counts though.
My old 5-speed Insight had 3 drive gears and 2 OD gears. (4th and 5th were both OD.)
For the OP, I have a Lexus hybrid AWD SUV and drive 'over the mountain' on my commute to work. The car has a CVT transmission with a 'D' and 'B' forward driving speeds. 'D' is the normal driving mode and 'B' is 'downshifted'. On the downhills over the mountain, I keep the car in 'B' mode and let engine braking help keep the car's speed reasonable. I purchased the car from the dealer as a lease return with 60k miles. It now has 160k miles and driving downhill in the mountains with the 'B' mode has not affected the car's mechanical reliability at all. Haven't had to replace the brake pads yet either. Was told the last time I was in the shop that they are only half worn.
Ah CVT's, so much good and so much fail in one transmission.
Down shifting to slow is not going to increase your mileage though. To get the best mileage you'd do just the opposite, that is, slip it into neutral to coast. I don't recommend that either, not with an automatic. (But I do that with my stick regularly, especially when headed downhill to a stoplight or stop sign, then slip it into a lower gear to brake (engine brake) for a stop or slip it into a high gear to continue through the light if it changes. Whether 2-3K rpm is more efficient under load is questionable. I believe it's usually around peak torque, but even that will vary by how hard you're pulling.
Downshifting to slow is marginally better than idling/coasting to slow on modern cars since most manufacturers incorporate DFCO (Deceleration Fuel Cutoff) which shuts off your injectors when the throttle is closed (i.e. car in gear and foot off the gas pedal). If you stay in neutral, you car still burns off the same amount of gas as if it were idling, but if your car is in gear, it burns no gas. Your car will still slow down because now the compression in each engine cylinder works as a friction brake that saps away momentum from the moving car, in addition to any brake usage you may use as well.
You've just described a 4 speed. OD still counts as a gear.
Most n-speed trans have n-1 drive gears and 1 overdrive gear. Still counts though.
My old 5-speed Insight had 3 drive gears and 2 OD gears. (4th and 5th were both OD.)
yeah, it is, it has the 41te fourspeed, second gat is labled 3, serves as second and third gear shift point- which is why it's faster on the downshift manual, versus doing it on it's own, most likely it goes from fourth gear to second. I had to look it up, you're right, which means it's as shown P-R-N-OD-3-1, with 3 serving as both second, and third manual gear selections, as it does shift again in 3 before it redlines. It'll run to 50mph before you need to shift in to od, or it shifts to od.
Your insight reminds me of the tremec t-56, which is a t5(although stronger) with a second over drive. I find it funny the tranny based on the t5 is stronger than the tranny it's based on, while the t5 itself still has that weakased 3rd gear.Time for some paradox im my own father engineering, to make the t5 based off the t56, eliminate that 3rd gear issue.
What about brake lights? If you suddenly downshift, there's no warning to the cars behind you.
If there are following you so closely that this becomes a problem for them....they are too close and it is their problem not yours.
On to the downshifting question....
I am not sure what RPM you are running after you complete your downshift but.... Most cars cut ALL fuel to the engine while your foot is off the gas. However, at higher rpms there is the chance this isn't the case of course it would be less efficient to do so. The only real way to know is to install a Scangauge or an Air / Fuel ratio gauge.
My only concern in downshifting with an auto is how it handles the down shift. Some autos will match the RPMs of the engine to the drive train perfectly. This results in a smooth downshift and wouldn't be very hard on the car. I drive a manual and match the RPMs on each downshift resulting a smooth downshift.
If your car doesn't do this the downshift would be abrupt as the engine rpm catches up with the drive train rpm possibly leading to more wear and in an extreme situation if you were in slippery conditions could result in a surprise.
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