D or N at traffic lights - another view

[philepo]

I stumbled across a few arguments about whether you should leave an auto car in N or D at traffic lights. I go into N more often than not.

Unless someone with knowledge of what exactly happens inside a g/box when it shifts from N to D can enlighten, I would say that the wear when the car is in motion is drastically more significant than at a standstill.

The g/box is changing gears all the time at anything from 2-6000 rpm which must (?) be a lot more wearing than shiftinmg from N to D.

Cheers.

 

[renault12ts]

The torque converter (in my car ) is a fluid drive. Holding in D at traffic lights will have very little effect. I stay in D 99% of the time.

 

[johnsco]

Leave it in "Drive" when temporarily stopped.
That's why you buy an automatic.

Cheers.
Johnsco

 

[whitenemesis]

I am no expert, so just my opinion and thoughts..

The autobox is coupled to the engine by a fluid drive, no mechanical connection.

Sitting at the lights in D means, torque convertor spinning, foot on brake prevents motion so no movement in gears.

Sitting at lights in N means torque convertor spinning, drive to rear axle disconnected and gears spinning, foot on brake.

Differences are in N gears are still moving, plus you have had to move selector so additional 'wear' as output shaft disengaged.

It's an auto, leave it in D.

 

[crockers]

I always leave it in D as I'm lazy... - but I was once told that I should put it in N incase I was tailgated and my foot slipped off brake and therefore making the car move forward...

But I don't...

 

[hitenhirani]

I am no expert, so just my opinion and thoughts..

The autobox is coupled to the engine by a fluid drive, no mechanical connection.

Sitting at the lights in D means, torque convertor spinning, foot on brake prevents motion so no movement in gears.

Sitting at lights in N means torque convertor spinning, drive to rear axle disconnected and gears spinning, foot on brake.

Differences are in N gears are still moving, plus you have had to move selector so additional 'wear' as output shaft disengaged.

It's an auto, leave it in D.

This why when selecting N, your idle revs will always go up ever so slightly, using more fuel.
thats what I found anyway...

 

[philepo]

I've no idea to be honest

Although its a fluid drive type coupling, we know that as you shift from D to N the revs rise as the load is released and also the car will roll forward in D without brakes on.

This is all wasted energy in my opinion and hence N should be selected.

And as I say, changing gears on the move is where the wear is as this is a high load clutch band operation whereas N to D is low load.

I could be quite wrong about that, but I like to save fuel and not have to keep foot on the brake - another form of laziness I guess!

 

[BTB 500]

Generally M-B's advice is to leave it in D

If you only need to stop briefly:

- Leave the selector lever in the drive position.
- Secure the vehicle against rolling away using the brake pedal.

That's the Vito handbook, pretty sure the SL one says something similar.

 

[Chattonmill]

Generally M-B's advice is to leave it in D

That's the Vito handbook, pretty sure the SL one says something similar.

What's a handbook Is it a girly thing like a handbag

 

[Gollom]

I leave in drive and set SBC-Hold so do not need to hold down pedals! :bannana:

 

[JAYGURNEY]

If its going to stop arguements.......dont stop at traffic lights.....

 

[Gareth]

SBC Hold

 

[Dryce]

SBC Hold

Definitely.

 

[louisv6]

SBC Hold

What's that? I feel like I'm missing out...

 

[Gareth]

What's that? I feel like I'm missing out...

when you come to a standstill you just press the brake pedal sharply to the floor and it holds the car, then you just accelerate to move off.

 

[Gollom]

What's that? I feel like I'm missing out...

When I have come to a complete stop I simply tap the brake pedal and SBC Hold comes up in my display. This holds the car with no need to keep my foot on any of the pedals. When I am ready to move off I simply press the accelerator. Especially good at traffic lights! Not sure if it is on your car. If you post the full model and year I'm sure someone will be able to tell you

I know it all has a chequered history and was removed fom later cars (urban legend has it that it was down to stupid Americans getting out of the car with it set and then suing MB when the car moved off ) Worthwhile doing a search on the forum as there has been much discussion.

 

[Buggerlugs]

It's fine to leave it in D for short periods, by that I mean, say, up to about 10 minutes, if you're gonna be stood for longer I'd recommend N.

WRT gearbox longetivity, the reason for selecting N is that when in D at a standstill is that ALL the engine power is being converted onto heat in the torque converter (none is being converted into kinetic energy), this extra heat in turn then purcolates throughout the transmission fluid resulting in an increase in overall operating temperature, not to mention an even more subtantially localised increase in the torque converter itself, the gearbox fluid cooling system is simply not effective enough to be able to dissipate this extra heat over a prolonged period of time. The number one killer of automatic gearboxes is........overheating.

 

[Shude]

I just leave it in D with my foot on the brake. If it gets to over a minute or two then I shift straight into P and take my foot off the brake again. I don't think I ever leave my car in N.

when you come to a standstill you just press the brake pedal sharply to the floor and it holds the car, then you just accelerate to move off.

So to answer the OP your car assists you in holding the brake while in D rather than shifting into N.

 

[prprandall51]

I know nobody is going to agree with me on this....

First, the highway code requires you to apply the park brake - not the footbrake or SBC Hold - as otherwise you will be dazzling cars behind you with your brake lights (which is especially irritating now that many of us are commuting to and from work in the dark at this time of year).

Secondly, if you leave it in D and are rear-ended, your car could well drive itself into the middle of the junction where you can be hit - hard - in your driver's side door. If you have the park brake on you have minimised the risk to yourself.

Third, if you have been driving vigorously up until the point where you stop (with plenty of heavy braking) then holding your car on the footbrake (or SBC Hold) can cause localised overheating of the discs at the point where they are clamped by the pads leading to brake disc warping.

 

[timskemp]

I know nobody is going to agree with me on this....

First, the highway code requires you to apply the park brake - not the footbrake or SBC Hold - as otherwise you will be dazzling cars behind you with your brake lights (which is especially irritating now that many of us are commuting to and from work in the dark at this time of year).

Secondly, if you leave it in D and are rear-ended, your car could well drive itself into the middle of the junction where you can be hit - hard - in your driver's side door. If you have the park brake on you have minimised the risk to yourself.

Third, if you have been driving vigorously up until the point where you stop (with plenty of heavy braking) then holding your car on the footbrake (or SBC Hold) can cause localised overheating of the discs at the point where they are clamped by the pads leading to brake disc warping.

Firstly - if you can find that in the highway code I'll be surprised. Every police car I see at lights sits with foot on brake. It makes sense to emphasise to the idiot approaching behind that you are stopped. If brakelights bother you can I suggest an eye test?

Secondly, the parking brake operates minimally and only on two wheels, the service brake clamps all four. Service brakes win again. My car was pushed less than one car length after being hit at approx 40mph from the rear with SBC hold on.

Thirdly, disc warping is highly unlikely, and the pads will conduct heat away from the discs also. I've not had any discs damaged in my years of driving autos, which tend to have better braking systems anyway due to the tendency for drivers to ride the brakes instead of selecting a lower gear on hills.