what's the use of "N" in a AT?

**Ry_Tower** · January 16th, 2016 06:42 PM

Originally Posted by newtocar

"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 D in that none of the clutches are engaged except in D 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.

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."

.....Taken from the net....

Source please, I highly doubt it. When in N there are actually no rubbing of internal parts. Parang may mali sa explanation. Why would car manuals specify to put the gear in N when in a prolonged stop?

http://www.topgear.com.ph/features/c...uck-in-traffic

**newtocar** · January 16th, 2016 07:26 PM

brakes - Use of Neutral Gear in Automatic Transmission - Motor Vehicle Maintenance & Repair Stack Exchange

**Ry_Tower** · January 16th, 2016 07:37 PM

Originally Posted by newtocar

brakes - Use of Neutral Gear in Automatic Transmission - Motor Vehicle Maintenance & Repair Stack Exchange

Hmm I guess they seem to think more gas consumption and more load to the brakes is okay. But I'll stick to what I think is best.

**newtocar** · January 16th, 2016 08:24 PM

^ it is always the operator's preference what to follow. If you look at the comments of TGP feature column (shifting to neutral ....) some disagree to TGP's reply.
Anyway, we own our vehicle, so we do what we believe right for it.

**oj88** · January 16th, 2016 08:33 PM

Originally Posted by Ry_Tower

Hmm I guess they seem to think more gas consumption and more load to the brakes is okay. But I'll stick to what I think is best.

You'll just have to balance it. While stopping for several seconds, it should be ok to leave it in D. But if the stop is going to be longer than a few minutes (or if you've been stationary for more than a while already), putting it in N would allow you to relax your foot. With the brake lights off as well, the driver behind you would be thankful.

Shifting it between N and D too frequently will theoretically add wear to the shifter linkages, as well as some added wear to the pertinent clutch (with the engaging and dis-engaging). Clutches don't wear out when they're either fully engaged or fully dis-engaged. It's when they first make contact in which a little bit of slip happens, is when clutches wear a bit of their friction material. So the idea is to keep the shifts to a practical minimum.

**timo07** · January 16th, 2016 09:30 PM

What about CVTs? Does it make sense to switch to neutral on traffic light stops?

**dr. d** · January 16th, 2016 09:47 PM

Originally Posted by Jeffrey Perez

So kung normal stop and go, ok lang na wag na ilagay sa N at D nalang? Sa US kasi, they really don't bother putting it to N unless 5 to 10 minutes ka naka idle.

putting it to N while idling, reduces the wear and tear that would occur should you put it in D.
the wear and tear will be in the engine, the trans box, and the brakes.
there might also be just a wee bit increase in fuel consumption..
the argument of N versus D for CVTs, are just like traditional ATs. see above.

no big deal, really. it's up to you.

**WallyWest** · January 17th, 2016 09:44 AM

After reading that argument that it's ok to keep it at D, I gave it a try this morning. My vehicle would slowly creep forward with the handbrake engaged. Handbrake issues or not, N na lang talaga ako for safety.

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**jick.cejoco** · January 17th, 2016 11:08 AM

Originally Posted by WallyWest

After reading that argument that it's ok to keep it at D, I gave it a try this morning. My vehicle would slowly creep forward with the handbrake engaged. Handbrake issues or not, N na lang talaga ako for safety.

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Free country, your car. But leaving it in D range prevents shift shock from N to D.

**timo07** · January 17th, 2016 06:45 PM

Originally Posted by jick.cejoco

Free country, your car. But leaving it in D range prevents shift shock from N to D.

I'm not sure if what I'm experiencing is shift shock but the transmission jerking is more pronounced from D to N than N to D. In fact, N to D is quite smooth and jerking is almost non-existent. Without stepping on the brakes or gas pedals, I can shift from N to D and the car will just start to move slowly on its own. 2015 Altis CVT.