Coasting Downhill in Neutral : Damaging to AT??

[twentynine]

Originally Posted By: SecondMonkey
Originally Posted By: twentynine
If the accident is the other guys fault or your fault, you are still in an accident. Right?


The point is, there is no accident. What you are describing is ridiculously unlikely, and again, anybody who caused it is stupid.

There is no reason you need to slow down at all when coasting down hill, that's the point of neutral. Like I said, I frequently coast for a full mile, ABOVE the speed limit. Even if I was to dip below the limit, it would take half a second to shift back into drive and hit the gas.

I will further repeat, if this happens, neither driver should have ever had a license.


Look I ain't trying to talk you out of nothing.

Ridiculously unlikely---- maybe unlikely, but not ridiculous. You know as well as I do that people-- all people make bone headed moves, ziggs when they should be zagging. Yes! Some one who got himself into this situation would be considered--- ugh --- unintelligent. Like I said though I have witnessed accidents that defy explanation. The best you can do for yourself is be on guard and hope you don't have one of those moments.

If you speed up to above the limit going up the hill, wouldn't you be undoing any savings that you would see on the other side of the hill coasting? Wouldn't just plain driving the speed limit with the cruise control set take all the unecessary accellerations and decellerations out of the picture?

Also ---- over the years I have seen hundreds of people young, old, rich and poor who should not be allowed to drive. But guess what, they are out there driving.

Look if you want to have your car towed down the high way with two mules, go ahead, ain't no sweat off my behind. The only point I was trying to make is/was we have to share the highway with a lot of people and not all of them are as capable as the average driver.

 

[Schmoe]

There was another post that Mr. Allen put out regarding the neutral-back in drive thing. I know, I asked and in the style of Mr. Allen, he said that shifting the AT out of D to N and then back to D is a bad thing. What your doing is making the AT pressurize off and on again. Akin to peddeling against a brick wall and all the tension on the chain, and then stop, and then pedal again. Eventually the chain, or something is going to break. Made perfect sense to me. And for what? To gain a .5 or so mpg advantage versus the costs of a new transmission?

 

[Drew99GT]

We need to define "downhill" as well. Coasting down really steep hills for a long distance in neutral will severely wear brakes out and potentially overheat them to the point you have no brakes. It's arguable if you'd actually increase fuel mileage at all, but you'll be putting brakes on your car 10 times faster if you coats down hills in neutral riding the brakes all the time.

 

[Drew99GT]

Originally Posted By: SecondMonkey
And to call it dangerous is ridiculous, you're just rolling down hill in full control.


PLEASE people, do not read this as fact. It's ludicrous actually, to put the transmission in neutral and coast down hills or mountains. It's dangerous as heck actually on steep enough terrain. You might get away with it in the Texas hill country, but don't take a trip to CO and try it down 7% grades on mountain passes that drop 4,000 feet in elevation. YOU WILL OVERHEAT THE BRAKES, and they will fail.

You lose eons of split second vehicle control when the engine is disengaged from the drivetrain.

 

[JHZR2]

damage? doubtful - weve done it for >200k miles in our toyota previa without issue, thr trans is still perfect. Turning off the engine without an output shaft driven AT pump is a no no...

Maintenance of momentum vs. drivetrain and air pumping losses is the biggest thing to me, IMO. Ive found that neutral allows me to do the maintenance of the momentum that I paid for thing more easily. There are times to use each.

If you know youll have to slow down or stop, staying in gear and using fuel cutoff is best. If you will keep going, neutral is best. If you know youhave a big hill right in front, staying in gear and accelerating downhill is good, then you shed momentum going up the next.

Doing the accelerate then glide as far as you can in neutral (or enmgine off) is kind of like the pulse and glide hypermiling technique, generally found toi be VERY beneficial...

JMH

 

[Gary Allan]

The bottom line in most of the rhetoric here is: nobody but you (whomever that may be) knows how to properly drive. Everybody else is "unright". Once you get passed this given, you can move on...

Now for the technical aspects of the practice ....?????

I'd say it's a wash ..but may yield something if downhills are long enough to bother with. Here in PA we have lots of "rolling hills". In this terrain it just works better run at the speed limit (or whatever) on flats.. and roll up to whatever gravity takes you too and use the momentum to carry you up the next incline. Hopefully you aren't in a speed trap at the bottom of one of the hills. They're way too frequent in the up:down thing to bother with shifting into neutral. Now in the mountains ..no way. Too steep and too long with too many curves.. when I know I'm at fuel cutoff and need the control just to save the brakes.

 

[Steve S]

Leave the trans in drive.

 

[twentynine]

Look here in La. the highest hill we have is the Sunshine Bridge over the Mississippi River and maybe a few interstate overpasses. So hill driving is not our thing.

It's funny 40 years ago I remember the Drivers ed movie telling us about down shifting on down hill slopes, to avoid overheating the brakes. 30 years later I was on vacation in Reno, Nevada driving a rented Dodge Neon. Up and down the hills I was giving them brakes he!!. Then it occurred to me, like a bolt out of the blue. This is exactly what the drivers ed was talking about. Dropped that auto transmission down into 2nd, guess what no more riding the brakes. Who ever thought of that had to be a genius.

Look generally I don't particularly care for the "hypermiling" stuff. I would say a lot of it depends on conditions of traffic, road and auto. Can you imagine being behind some one on a curvey hill laiden road who is using the pulse/glide technique. One minute he is way out a head of you, the next minute he is right off your front bumper. You try to pass him, but oh no it's pulse time, he runs away from you. So you decide to hang out behind him, oops, it's glide time, now he's right off your front bumper and slowing down. From everything I can read "hypermiling" does not make any considerations for the million other drivers on the road that are trying to get to their destination in a reasonable manner.

I might go for the shifting a manual stick into nuetral and letting her coast, turn the engine off NEVER! Can you imagine going one click to far and locking the steering wheel, holy [censored], things would get interesting then. Not to mention loss of brake boost, power assist steering, intrumentation and so on. As far as an auto, as I have said earlier, when I have a zero throttle setting the transmission unlocks and it's basicly in nuetral anyhow, so actually moving the shifter to N is not necessary.

The deal about accidently shifting to R instead of N, well like I said I ain't to sure but I know the transmission on my truck is electronicly controlled, and I know I can't shift to R if I am moving forward. Or atleast the transmission won't actually shift into reverse if I am moving forward.

The truck is really interesting, electronics are a wonderfull thing. Like if I lock the doors getting out of the truck, but the keys are in the ignition. When I close the door the drivers door will unlock. Amazing!

 

[The_Jeff]

People need to play with their cars, parked in their driveways.

You can go from R or D to N without pushing the button on a console shifter, or pulling back on a column mounted one. One needs to go through additional work to get it into a moving gear. This is a safety thing in case the gas pedal gets stuck.

On my car, but maybe not yours, one has to turn the key to "lock" and actually remove it to lock the steering column. Any car made in the last long while, if you turn the key counterclockwise a bit, the motor will go off and you can still steer. It may or may not be labelled. 80's GM cars with "ACC" further around than "lock" still have an "off" position between "lock" and "run".

Back in the 1950s (!) the NHTSA or its predecessor decided the highways would be safer if all automatics had the same shift pattern; GM got the shaft and had to retool to match the PRNDL standard.

If one pays attention they'll notice some universal "rules" on american cars, that apply on rentals etc too, as well as the specifics on their own cars. Shoot, reading the owner's manual cover to cover explains most of them.

 

[twentynine]

Originally Posted By: eljefino
People need to play with their cars, parked in their driveways.

You can go from R or D to N without pushing the button on a console shifter, or pulling back on a column mounted one. One needs to go through additional work to get it into a moving gear. This is a safety thing in case the gas pedal gets stuck.

On my car, but maybe not yours, one has to turn the key to "lock" and actually remove it to lock the steering column. Any car made in the last long while, if you turn the key counterclockwise a bit, the motor will go off and you can still steer. It may or may not be labelled. 80's GM cars with "ACC" further around than "lock" still have an "off" position between "lock" and "run".

Back in the 1950s (!) the NHTSA or its predecessor decided the highways would be safer if all automatics had the same shift pattern; GM got the shaft and had to retool to match the PRNDL standard.

If one pays attention they'll notice some universal "rules" on american cars, that apply on rentals etc too, as well as the specifics on their own cars. Shoot, reading the owner's manual cover to cover explains most of them.


Hang on I'll go give it a try!

 

[Camu Mahubah]

I used to think coasting downhill in neutral was a good idea until my brother borrowed my 78 Pontiac Grand Prix last summer.

When I handed him the keys I gave him a set of rules:

1. No Riders!

2. No Driving After Dark!

3. No Leaving Town!(Interstate Excursions)

He's been in trouble with the law and I don't like some of his buddies. The headlights were known to short out at the worst possible time. And This car needed tires so I felt it was unsafe on the Interstate.

What's he do...

That afternoon he picks up a chick and heads to Denver 280 miles away! Calls my wife while I am at work and tells me made to Denver just fine but on the way back through Cheyenne the car started knocking! He left it at a truckstop!

I was livid! To shorten this story a little bit I found out he was shifting into neutral going downhill to save gas. And then shifting back into Drive at 75-80 mph. Now this transmission was old and had a lot of miles, but I had just changed the filter and the fluid didn't look so bad and it had a Wix gasket so I knew this transmission had seen a filter swap before.

I found out the transmission had boiled it's fluid out of the case. Finally it gave up and the engine decided to die also. I believe the hot transmission killed the engine. Must have been really hard to turn that hot transmission over at freeway speeds with only a third of it's fluid in the case.

Bottom Line(what I learned): Don't coast downhill in an older car equipped with an automatic especially at freeway speeds.

When I am in the mountains I turn the OD off in my Focus and that seems to help with the brake issue. I do not coast. And of course I don't pretend to be 100% Right About Anything Just My Opinion.

 

[twentynine]

Okay!

In drive engine on--- brake booster works, power steering works
In nuetral engine on --- brakes and steering just like drive

Engine off in drive--- no power assist on brakes, no power steering, however the key will not turn to lock unless the shifter is moverd to Park.

Engine off, shifter in park, ignition in lock --- steering wheel still turns.

Key removed--- wheels still turn wheel didn't lock.

Engine off, key in, ignition on---- shifter can be moved from park to reverse-nuetral-drive freely. Moving back toward park from drive, I encounter a detent going from nuetral to reverse. I have to pull the shifter back. Same thing if the engine is running.

Engine off, ignition on--- nuetral selected truck rolls forward. drive selecetd truck rolls forward. Interesting though- reverse selected and the truck still rolls forward. With virtually no brakes.

Right off hand, I'd say as long as you leave the engine running, shifting to nuetral would not compromise control outside of having to deal with one more issue in the event of an emergency. With the engine off, nuetral selected, you have no brake boost or power steering. That is a horse of a different color. No way engine off is safe unless you are totally alone on the highway. Don't know about you guy's area but mine. I ain't never alone on the road. Then maybe, if you are top knotch on your game, go a head.

I think I will continue to do what I have always done, speed limit or speed set according to flow of traffic, on cruise control.

I don't really feel the need to apologize, I never called any one stupid or questioned any one here driving ability. What I did do was question the safety of driving with the engine off or in nuetral. I still have concerns in relation to safety. Not the hypermiler, but the people who encounter the hypermiler on the highway. What I am looking at is if you are pulse/glide-ing your speed has to be varying much more than all the traffic around you. Part of driving safely is signaling your intentions and doing what the other drivers around you expect. Pulse/glide, how in the heck do anticipate that? The hypermiler knows what he is doing, the fellow coming up behind him does not, unexpected decellerations, not good.

So: I am sorry, I have a differing opinion.

 

[SecondMonkey]

Originally Posted By: Drew99GT
Originally Posted By: SecondMonkey
And to call it dangerous is ridiculous, you're just rolling down hill in full control.


PLEASE people, do not read this as fact. It's ludicrous actually, to put the transmission in neutral and coast down hills or mountains. It's dangerous as heck actually on steep enough terrain. You might get away with it in the Texas hill country, but don't take a trip to CO and try it down 7% grades on mountain passes that drop 4,000 feet in elevation. YOU WILL OVERHEAT THE BRAKES, and they will fail.


I don't know how smart you are, or anyone else here, but I think it's quite obvious to know when you can shift into neutral and coast at the right speed and when you can shift into neutral and end up on a run away train. We're not talking about MOUNTAINS here, we're talking about HILLS!

If you have to hit the brakes, then you shouldn't be in neutral. It's that simple.

 

[moribundman]

Reminds me of the movie 'The Englishman Who drove Up a Hill But Flitted Down a Mountain.'

 

[Drew99GT]

Originally Posted By: SecondMonkey
Originally Posted By: Drew99GT
Originally Posted By: SecondMonkey
And to call it dangerous is ridiculous, you're just rolling down hill in full control.


PLEASE people, do not read this as fact. It's ludicrous actually, to put the transmission in neutral and coast down hills or mountains. It's dangerous as heck actually on steep enough terrain. You might get away with it in the Texas hill country, but don't take a trip to CO and try it down 7% grades on mountain passes that drop 4,000 feet in elevation. YOU WILL OVERHEAT THE BRAKES, and they will fail.


I don't know how smart you are, or anyone else here, but I think it's quite obvious to know when you can shift into neutral and coast at the right speed and when you can shift into neutral and end up on a run away train. We're not talking about MOUNTAINS here, we're talking about HILLS!

If you have to hit the brakes, then you shouldn't be in neutral. It's that simple.


You shouldn't be in neutral with the engine running and the vehicle moving. It's that simple.

 

[moribundman]

Originally Posted By: Drew99GT
You shouldn't be in neutral with the engine running and the vehicle moving. It's that simple.

It's illegal in most jurisdictions and with good reason: lack of common sense of the average four-wheel jockey.

 

[SecondMonkey]

Originally Posted By: Drew99GT
You shouldn't be in neutral with the engine running and the vehicle moving. It's that simple.

You are simply wrong. You have no evidence to back that up.

 

[moribundman]

Overrun cut-off (deceleration fuel cut-off) works only if the transmission is in gear. If you a have a vehicle that displays instant fuel consumption it is easy to see that fuel consumption with overrun cut-off drops to 0.

 

[Gary Allan]

Originally Posted By: SecondMonkey
Originally Posted By: Drew99GT
You shouldn't be in neutral with the engine running and the vehicle moving. It's that simple.

You are simply wrong. You have no evidence to back that up.



Well, all things being equal ..I tend to agree. It's hard not to be in neutral with a manual transmission with the engine running. I don't see any clear cut distinction between auto and manual in the action itself

Now it can surely be more awkward for the novice ..much like driving a manual and coordinating 4 elements at once (steering, throttle, clutch, and shifter) ..but some actually manage to make it through an entire day without screwing it up.


As the esteemed mori said, it's illegal AFAIK ..but then again, many of us push the boundaries of many regulatory envelopes in our driving lives.

 

[twentynine]

I can't believe it is against the law to be in nuetral.