To answer your question, you can switch to B-mode at any time/speed (from D-mode). As soon as you engage it, engine pumping will begin, to waste energy and slow the car down (slowly) (unless the gas pedal is engaged, in which case B-mode will do nothing more that D).
Can we Shift from D to B While Driving? The answer is yes. You can always shift from D to B while driving. The physics of cars allows this shift of gears.
Avoid changing gears while the car is moving
The car will actually stop but you will end up wearing out your automatic transmission band. The transmission band is hard to access making its repair and replacement expensive and time-consuming.
It is widely believed that switching the car to the neutral mode while driving will save fuel. However, it is dangerous to do so. Switching to neutral will reduce the control you have over the car. This can prove to be life-threatening in a risky situation.
Can i shift my automatic transmission from D to 3, 2 or 1 without stopping the car? Yes you can. It's handy for towing and steep hills. Assuming you're talking about an automatic/standard, all it does is limit the highest gear it'll use.
Keep in mind: Never switch from high-range 4WD to low-range 4WD while your car is moving. While switching from 2WD to 4WD while moving isn't likely to hurt your car, switching between the two 4WD modes while moving can significantly damage your gearbox and differential.
In some vehicles, you can “shift on the fly" from 2WD to 4WD and back, but with some you must stop first, or much damage can be done. Read the owner's manual for your vehicle. On four-wheel drive trucks, the manual says not to use the 4WD function on rough terrain.
Using the D3 gear on the highway is not recommended or safe. Ideally, D3 should only be used for gaining uphill speeds during heavy traffic (stop-and-go situations). Even if you can safely use D3 on a highway, it creates unnecessary wear due to the higher RPM.
What if you're driving and it shuts off? If you manage to turn off the car while in drive, it won't harm your vehicle, and you can simply turn it back on again. If you're moving, however, you'll notice the car is harder or impossible to control as the electronics won't work unless the vehicle is on.
Shifting to neutral from drive while moving will do nothing at all. Assuming this automatic vehicle has a torque converter, when you shift back into drive, the computer will select an appropriate gear for your speed, (usually the one you were just in, unless you've slowed down) and place the vehicle into it.
If you shift too early, you run the risk of lugging your engine, asking it to move your car forward at an unnaturally low RPM. For more details, and a side-by-side comparison of the fuel efficiency achieved in 2nd, 3rd, 4th and 5th gears at identical speeds on the same stretch of road, watch Fenske's video below.
With skipping gears on downshifting, don't shift down to a gear that'll cause your engine to exceed its redline. That can potentially require a very expensive fix. A simple rule of thumb is to skip no more than two gears at a time.
WARNING: When your vehicle is stationary, keep the brake pedal fully pressed when shifting gears. Failure to follow this instruction could result in personal injury, death or property damage.
Put simply, the 'D' mode is for normal driving, and 'B' mode should be used when you are going downhill.
The transmission will change to a lower gear when you put the car in "B," allowing you to utilize the engine to slow it down rather than simply the brakes. This can be helpful if you're descending a steep hill and want to maintain the control of your car.
B mode is BMWs one pedal drive mode and the car will come to a complete stop and hold ( no creep ) when in this mode. The normal D position will take into account personal settings for High, medium, low & Auto however the car will not come to a complete stop without the use of friction brakes in this mode.
Your vehicle will stall and you may hear a grinding noise.
If by chance your vehicle is not equipped with a reverse inhibitor, or it is malfunctioning or broken, putting your automatic transmission in reverse while driving will more than likely stall the engine.
After the play ends, we see Misaki in the present, shopping for groceries in Korea. As she leaves the store, she gets into Yasuke's red Saab, and she drives away, having removed herself from Japan, a place that tormented her and prevented her from moving past her feelings of sadness and regret.
We'd recommend using this when you're driving in heavy traffic around town or travelling down a steep hill. At higher speeds, it's better to stick with 'D' mode and let the car coast when you lift off the accelerator. You don't want it slowing down of its own accord at motorway speeds.
You will not gain any performance advantage, or gain in fuel economy, by driving around town with the shifter in the 3 setting. For the best performance, simply put the shifter into the D (or drive) position and drive normally.
In “D” mode, the car may even shift into higher gears to warm up the engine faster in cold weather. When “D3” is selected, the car will automatically shift between the first three gears, but will not shift to a higher gear.
Don't try to engage these 4 wheel drive systems when the vehicle is moving or you can damage expensive components. However, most 4WD systems can now be shifted into or out of 4WD on the fly at the push of a button. The most sophisticated 4WD systems are fully automatic.
You can move the control from 2H to 4A or 4H at a stop or while driving.
Shifting into low-range four-wheel drive is a little more involved than shifting into high-range four-wheel drive. Drivers will need to shift the transmission into neutral to disconnect torque to allow the transfer case to shift gears.