I am new to driving A/T cars and I am trying to understand the use of Neutral(N) gear. Should I shift my gear from D to N when my car comes to a complete halt on a red light or somewhere else? As per my understanding, putting brakes on while waiting on a red light while your gear is in D can damage the braking system?
For general driving, you can leave the car in drive. It doesn't damage the transmission leaving it in drive while stationary at the lights - although you don't want to be doing silly things like revving the engine while holding the brakes on.
In an automatic car, you don't really use neutral. It is a step on the way to selecting Park, which means that the transmission is disengaged.
The main purpose of neutral on an automatic is for towing or pushing the car. Obviously you can't push it with the transmission in park, and if you tow it with the transmission in gear or in park and the drive wheels are in contact with the ground, you'll ruin your transmission or your tires or both. I'm sure there are some other uses too, but they're sufficiently rare that they probably don't need to be mentioned.
When the car is in D and you start the engine the hydraulic pump in the automatic transmission is not providing fluid pressure until the engine starts.
This fluid pressure is used to engage clutches in the transmission to engage first gear or reverse.
An automatic transmission does not have gears like a manual transmission which are physically meshed into one another or engaged.
The gears in an automatic transmission are always engaged or locked in but they are coupled to the drive shaft by multiple different clutches that are selected either by you or automatically. This is called the planetary gear and clutch system and it is very difficult to conceptualize.
In an automatic transmissions N is actually the same as P in that none of the clutches are engaged except in P there is a mechanical connection to an internal transmission brake. This brake has nothing to do with your wheel brakes and it come on mechanically so the engine does not need to be running for it to work. But you should not rely on it alone when parking on steep hills.
In D when you’re at a stop the main forward clutches are engaged and the torque converter is providing pressure to rotate the forward gear but it does not rub or wear when it is doing this. Because of this resistance to free rotation in the transmission the engine begins to slow. In a modern car there is an idle control valve which the computer opens to increase air entering the engine so the engine does not stall. So there is actually more air entering and the computer senses this and adds a bit more fuel as well. So in D at the light your car will use a little more fuel than if it was in N.
Also the wheel brakes are not rubbing but are stopped and they will not wear at all while holding the forward creep of the car when in D.
The forward creep is caused by the transmissions torque converter. There is nothing slipping or wearing or heating up to any significant extent in there. It’s all done hydraulically and nothing is wearing to worry about. BUT!!!! When you are in N and the engine is turning and the wheels are stopped then for this to occur the main forward clutch is disengaged and it is SLIGHTLY SLIPPING. So the clutch plates are wearing.
So you are actually wearing out the main wear component in an automatic transmission being the clutch plates if you shift from D to N at a stop. The only advantage is your saving a very small amount on fuel.
Personally I DO NOT and I have been told by an automatic transmission engineer that you should never shift the transmission from D to N at the lights. The reason being you are wearing your clutch plates in your transmissions. It also gets hotter because of the friction and the dirtier transmission oil then contributes to other component failures.
Also it’s dangerous to be sitting there in N. You may need to drive away all of a sudden to avoid an accident but in N there is less chance of do this. You also may select the wrong setting like R when you wanted D.
If N should be selected at the lights then engineers would have incorporated this into the design. But they did not. On some fuel saving cars the engine now shuts off at the lights so obviously N is selected automatically by the computer during the shutdown period so the car can be restarted. But the engine is not turning so the clutch plates are not slipping and wearing in this type of fuel efficient car.
Also if your car vibrates in D at the lights then you need to get it serviced. It should not vibrate excessively at the lights if everything is working fine.
putting brakes on while waiting on a red light while your gear is in D can damage the braking system?
In general, no, you're fine.
I think you've conflated several issues that can lead to issues (if not actual problems):
If you were sitting at a light in drive (D) with your left foot on the brakes hard and your right foot flooring the accelerator, your transmission would become extremely annoyed with you, not your brakes. This is what Rory is describing and, while it's not strictly what you're asking, I'll second his advice: don't do that.
If you just quickly decelerated from high speed (as in, you were going too fast and stopped very quickly), your brake discs will be quite hot. As you can see from Larry's picture, most of the disc will be able to radiate heat. However, the area that is tightly gripped by the pad (since you're preventing the engine from carrying you forward) is effectively enclosed in a suffocating glove of brake pad. This can leave a residue in that spot and will eventally lead to annoying vibration under braking. In this situation (which I try to avoid), I would be tempted to put the car in park, not neutral.
Like the others have said, neutral is almost never used. It does provide a modicum of comfort, though, to know that reverse and drive aren't immediately adjacent in your gear selection....
Neutral is there for special cases, such as if/when the car needs to be pulled up onto a flatbed for towing. Other than cases like that, you can just pretend that the "N" notch doesn't even exist. :-)
It's not a problem to leave the car in drive; I'd call it more a matter of personal preference.
While the car is idling in D and stopped, the automatic transmission is sort of in a 'ready-and-waiting' mode, with the torque converter partially engaged. This puts a little bit of drag on the engine, and requires the engine management system to deliver a little more fuel and air to keep the idle speed constant. This excess energy is discarded by the transmission as waste heat.
Certain vehicles exhibit more of this than others, but you may actually experience better fuel economy if you let the car idle in neutral instead of drive when stopped for longish periods of time.
I've definitely driven in thick traffic where I was stopped for minutes at a time, and found it far more comfortable to bump the transmission into neutral when the rate of progress was particularly bleak.
The brakes on your car are designed to stop and hold your car whether it is automatic transmission or manual, under what is considered normal driving circumstances. In response to the comment about neutral for towing your car, putting an automatic transmission in neutral and towing for long distance will tear up the tranny. 20 miles or less you should be okay. If all four wheels are on the ground, the drive shaft turning is also turning gears in the transmission. The gears are meant to have the pump in the transmission moving the fluid around to keep everything lubricated and cool. Without the pump working, the fluid will get to hot and cause damage to the integral parts.
depends on your car newer cars have electronic controlled transmission which will unlock from D (first gear actuator) if your stopped and not pressing the gas pedal.how ever on most of the cars new and old its a good practice to keep it in N if you stopped.
leaving the car on D and pressing the break will just load the transmission and heat the fluids in it because the first gear actuator will be engaged thus loading on your torque converter bump which causes the fluid to heat up. keeping it on N will will disengages any load on the transmission and will elongate its life.
as i said its good practice will increase your transmission life time
Torque converters don’t have “Dumps”. I think this person is taking about the pressure relief valve which is relieving hydraulic fluid pressure created by the transmissions hydraulic oil pump. The oil pump is driven direct from the engine. It is independent from the torque converter. The pump is working if the transmission is in any selection. So in N it is still working. There will be no difference in heat created from the fluid pressure either in D or N. The difference is in N the main clutch is disengaged and is forced to slip and wear also giving off additional heat. It’s the reverse to what this person said. So keep it in D at the lights which is what the engineers designed the car to do.
I don’t think putting breaks for long time harms enough the breaking system. When we are talking about car with automatic transmission then its breaking system is also designed by keeping in mind about its rough use. Shifting Gear from D to N will make your car neutral that disconnect the engine from wheels using transmission. It is usually done when you need to push your car or have it towed. Therefore be relax, putting break will not damage your breaking system.
the only way to reverse while the car moves is if you change from d to n then r but do not accelerate or the car will use its momentum and transfer that physical energy directly to the engine which will cause the transmission parts to suffer greatly (specially the clutch, with standard Automatic transmissions, not CVT.)
protected by DucatiKiller Mar 6 '16 at 17:36
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