Good Morning Oppo....I have a question

"Mr. Ontop, No Strokes, No Smokes...Goes Fast." (twostrokesmoke)
06/03/2014 at 12:21 • Filed to: None

I've heard that it is bad to glide downhill in neutral. If that true of all trnsmissions or just automatic...and why?

Here's a Mini for your trouble. This guy will put it wherever you want it.

DISCUSSION (40)

macanamera > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:22

I don't think that's bad...

spanfucker retire bitch > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:23

I've never heard that, and I do it every day in my car.

Singhjr96 > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:23

Well the tranny is not connected to anything, so.... I'm guessing it's not bad. I mean your are moving forward, but the wheels themselves are turning the tranny... My guess is not. But don't take my word for it. Definitely don't do that.

Zipppy, Mazdurp builder, Probeski owner and former ricerboy > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:24

Not at all. there's nothing linking the wheels to the rest of the gearbox.

TheBaron2112 > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:24

I think it's bad purely because your car is not being powered by anything besides gravity. So if you need to suddenly accelerate, you can't (unless you shift back into gear). It's easiest to just keep it in gear and keep your foot off the gas if you want to save fuel.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > spanfucker retire bitch
06/03/2014 at 12:28

Me too... But I was stuck in traffic and had time to think....I couldn't figure out why it might be such a bad thing.

Roberto G. > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:28

It's bad and DANGEROUS, because all the braking action is done by the brakes, that sooner or later will overheat and fail. And this is both true with automatic and manual gears, even if the best engine braking action is achieved by engaging a low gear, with a manual transmission.

A couple of posts from the net:

With your car in neutral you don't have any drag from the engine, which you need going down hills so you don't cook your brakes. Changing down gears (auto or manual) when going down steep hills stops the vehicle from moving too quickly, and stops you from dragging the brakes to stay at a safe speed. If the braking system overheats and the brakes start to fade, ( need to be pushed harder and harder to maintain braking capability) you will soon have no brakes while rolling down a hill in 'angel' gear. I must be way out of touch with modern vehicles, because I've been taught ( advanced driving of cars, heavy vehicles, heavy off road vehicles) that coasting in neutral at any time is extremely dangerous. Burf is correct in saying that fuel economy is achieved in modern cars by the car's own management systems. You may save fuel, but it may cost a life.

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It's never really a good idea to shift to neutral when driving downhill, regardless of the type of transmission you have. In neutral, you're just freewheeling downhill and don't have as much control over the vehicle. Depending on the steepness of the downhill grade, and whether or not you're towing/hauling, if anything you should downshift to a lower gear; this will save A LOT of unnecessary wear and tear on your brakes, because you won't need to use them as much to control your descent. In other words, what you save in fuel costs by freewheeling downhill in neutral will most likely result in the premature need for a major brake job costing BIG BUCKS. I would most definitely NOT recommend the practice of coasting down any hill in neutral.

duurtlang > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:30

Bad? Not really, but I certainly don't do it myself. Leaving it in gear without pressing the accelerator actually saves some fuel due to the engine braking and depending on the incline you're less likely to be required to use the brakes, preventing brake wear and possible overheating brakes.

twochevrons > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:31

Personally, I think that it is a bad idea in terms of driving technique (no engine braking, you don't have the ability to get on the power quickly if necessary, and you'll use more fuel since you're defeating the car's ability to cut the fuel supply while coasting). Mechanically, though, I don't think that there's anything wrong with it.

Coasting in neutral with the engine off is another matter. Since most gearbox oil pumps are driven by the input shaft, lubrication will be severely compromised. That's why car manuals have dire warnings about towing a car with the driven wheels on the ground.

Opposite Locksmith > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:31

Because you have to use gas in order to idle the engine, as opposed to using the engines momentum to spin the engine

v8corvairpickup > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:32

Some places will consider the driver to not be "in control" when the vehicle is not in gear and coasting downhill. If the car is running, the only real issue is that you are putting stress on the driveline when you re-engage the transmission and the engine comes up to speed.

If you turn off the engine on an automatic transmission, some transmissions can be damaged by the lack of lubrication.

BoulderZ > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:32

In a manual, no problem. I've never heard that about automatics but maybe some of the newer ones are pickier? Functionally, though, it depends on the hill. Some of our twisty big hills here (like Trail Ridge Road, Berthoud Pass, or Vail Pass) would get your car going way too fast and/or you'd be on the brakes way too much, overheating them. We see this all the time, with flatlanders stinking up the highway with smelly, overcooked brakes. Sometimes you'll even see some of the brakes smoke or catch fire from overuse. One benefit of keeping it in gear is that most EFI systems will actually cut fuel at high vacuum, i.e. engine braking, which will burn less than if you're in neutral and coasting, just letting the engine idle. But, those might be more unusual hills, too.

RotaryLover > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:33

Nothing bad in a manual transmission car, if you know in which gear to put it in. In a automatic...I'd make sure that you can manage to keep rolling on neutral til the stop sign. It's not a good ideal to switch from N to D IMO. The issue there is mostly about picking up speed because of the downhill and your brakes. It's best to leave the car in gear to help brakes and not overwork them.

Mathias Rios > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:34

I know that with an automatic transmission, the transmission has to be in gear for fluid to flow and thus, cool the transmission. So there's a chance for an overheat. But in a manual I don't believe this is true.

thebigbossyboss > Roberto G.
06/03/2014 at 12:36

Mind you it all depends on what your doing...if your just coasting down hill 30 ft in traffic...yeah go for it. If it's a large hill I wouldn't recommend it.

McMike > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:36

If you're trying to save fuel, stop it.

Idling (which is what your car does in neutral) uses fuel, coasting your car on overrun doesn't.

I say leave it in gear, there is no advantage to putting your car in neutral on hills.

ly2v8-Brian > BoulderZ
06/03/2014 at 12:40

Neutral in an Automatic means no hydraulic pressure on the clutchpacks.

Roberto G. > thebigbossyboss
06/03/2014 at 12:40

IT'S ALWAYS REPEAT ALWAYS WRONG TO PUT A CAR IN NEUTRAL WHILE IT'S RUNNING. NO MATTER IF IT'S IN YOUR GRANDMA'S BACKYARD OR ON A HIGHWAY. YOU MUST ALWAYS REPEAT ALWAYS KEEP A GEAR ENGAGED. PERIOD.

BoulderZ > ly2v8-Brian
06/03/2014 at 12:43

Ah, wondered if there weren't something peculiar to the autos. Thanks for the insight!

thebigbossyboss > Roberto G.
06/03/2014 at 12:47

If free driving, I agree with you. I never put it in neutral. However, if moving 30 ft in stopped traffic on the downhill...you don't need to gear. You can barely gear anyways.

Roberto G. > BoulderZ
06/03/2014 at 12:47

Destroying the brakes to save fuel, is just idiotic. And a criminal offence in many places.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > Roberto G.
06/03/2014 at 12:51

WHY ARE YOU YELLING?

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > BoulderZ
06/03/2014 at 12:53

Yeah, I can see it being bad for the CFT transmissions for a new reasons.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > ly2v8-Brian
06/03/2014 at 12:53

Best answer so far.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > McMike
06/03/2014 at 12:55

My car gets more than 40 mpg, so it's not even a matter of saving fuel. It was just a question that I thought of while sitting in traffic.

ly2v8-Brian > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 12:56

LOUD NOISES

ly2v8-Brian > Roberto G.
06/03/2014 at 12:59

Very True. Transmissions are important for braking.

HammerheadFistpunch > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 13:08

I think what you've be hearing is that its bad for economy to coast in neutral....which is somewhat true in a modern fuel injected vehicle. In a fuel injected vehicle a closed loop situation occurs when you are above idle revs and closed throttle body shuts off the injectors so you are using no fuel, though you will be decelerating. with Carbed engines, its all about low rpm.

BoulderZ > Roberto G.
06/03/2014 at 13:08

I suppose if you found a way to use brakes to save fuel, that would be dumb. But staying in gear on a descent conserves both, as I mentioned, is safer, and is usually the law. A quick search of the 23 state codes available online shows it's a traffic offense to coast downhill in neutral in 16 of them, and legal in 7. Not a criminal offence in any of them, though.

thebigbossyboss > ly2v8-Brian
06/03/2014 at 13:11

I was talking about stop and go traffic...on an incline. I am not going to wear out my brakes slowing from 5 mph to 0 mph.

ly2v8-Brian > thebigbossyboss
06/03/2014 at 13:14

Yeah you'd be alright at that speed.

BigBlock440 > ly2v8-Brian
06/03/2014 at 13:37

What if you don't want to brake?

Cé hé sin > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 15:01

You can get trucks (commercial ones that is, with automated manuals) that will do this automatically if you are going down a gentle gradient so I guess that their makers consider the idea safe.

You can see it in action on this typically terrible you tube video here

Roberto G. > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 16:53

Because these are important concepts and deserve to be carved in stone: they need to pierce the thick outer atrophized layer of too many brains around here, to be effective.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > Roberto G.
06/03/2014 at 16:54

Well, at least I have helped contribute to intelligent car related conversation around here.....Now, back to the fat jokes and boobie pics!

Roberto G. > Mr. Ontop, No Strokes, No Smokes...Goes Fast.
06/03/2014 at 17:07

..and the style is that of the urgent messages on the old telex machines , that I used in my first job. Ah, memories...

Kinja'd!!!

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > Roberto G.
06/03/2014 at 17:49

I've only ever seen one, never in use though.

Two Drink Minimum > Roberto G.
06/03/2014 at 18:03

Yikes

Roberto G. > Two Drink Minimum
06/04/2014 at 13:15

Really, I wanted to make it clear enough because I care for the well being of all my friends. Honest.

Two Drink Minimum > Roberto G.
06/04/2014 at 16:44

Hehe. I believe you. And you are much more persuasive with the caps-lock off.