Coasting in Neutral???

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I have 2001 Acura Integra GSR Stick shift, is it safe to just coast in neutral down hill or will it prematurely wear out my transmission? I have read about some people who practice hypermiling and alternate
between neutral and drive. What do you guys think?
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I know that practice is illegal and reduces the amount of control you have with the vehicle.
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In article

Define "downhill".
It won't wear out your transmission, but in general it's not safe to coast for much of any distance. The issue is being ready to accelerate the car. You have to be in gear to drive it, and if you're not in gear when you suddenly need to be, you're in trouble.
Also, for long downhills you want engine braking so you want to be in an appropriate gear that keeps you from using your brakes excessively. Coasting just gives you a runaway car, and constant braking just wears out your brakes and possibly overheats them.
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googamooga wrote:

see what others wrote on legal and wear.
regarding fuel consumption, injection systems cut off fuel delivery entirely on over-run, i.e. when revs are above say 1,600rpm and there is no throttle. if the engine is idling, then it's still delivering fuel. translation: idling uses more gas than engine braking so don't do it.
lots of things you can do to improve mileage. good quality plugs and ignition system. ensure timing is correct. air filter is good. etc. and one little thing that i switched onto recently, making sure the tw sensor works ok. i had a couple in my civic that "tested" ok, but both were aged, and among other things, caused the computer to think the motor was colder than it really was, and thus inject more gas. my mileage has improved about 10% since i replaced it. your car is reaching a similar age. new ones cost ~$25 from online honda parts dealers.
a new oem honda thermostat is a good idea too, but just for reliability reasons.
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'97 Civic and when he's rolling down hills, he engages the clutch to "roll in neutral". I have told him that I didn't think this was a good practice but can't explain why it might be bad for the clutch. Can someone explain for me: 1-is this bad for the clutch? and 2-exactly why? Thanks, Rosscoe
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Just Me wrote:

being held open for extended periods of time, I can not think of anything. He will learn to stop doing that when you make him pay for the rattling throwout bearing!
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Exactly, premature wear. The same reason it isn't a bad idea to shift into neutral at a stop light and release the clutch pedal, versus sitting there in gear holding the clutch pedal to the floor.
And I agree with the comment on coasting in neutral versus remaining in gear. I typically roll up to a light in the highest gear I can, for as long as I can until the engine starts to lug, before I disengage the clutch and allow the car to go into idle. As noted, no fuel is delivered while you're coasting in gear, but some is when you're coasting in neutral (i.e., engine is idling).
Dan D '07 Ody EX Central NJ USA
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On Wed, 02 Jul 2008 09:11:34 -0700, Dano58 wrote:

Of course there is fuel being used while coasting in gear. The engine is still running, is it not? Therefore it's using fuel. No different than idling in neutral in that respect.
--
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Ok what if I am going down a slight hill (not mountain hills) at 40 mpg, then shift to neutral...ride it out for a few seconds then back in gear so I can go up the next hill? I would stay in gear but that slows me down so I can't take full advantage of the hill and the momentum.
How would being in neutral while riding would wear anything out? Can someone explain that to me in full detail please.
Thanks
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It's not the neutral part that wears things out, it's the getting back into gear afterwards that does.
Ever notice how it takes a bit of pushing before the lever will drop back into gear again? That's your synchros grinding themselves into powder.
If you push the clutch, rev the engine up to where it will ultimately be and hold it, lift the clutch, push it again, quickly drop the lever into gear and lift the clutch again, and get all this juuuust right, then there will be little wear to the synchros.
It's called "double-clutching". Look it up. It adds a lot of fun to driving a manual transmission.
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Tegger wrote:

I thought doulbe-clutching was before the days of synchros. Heck I shift without cluching, LOL. Those days are over for me too. My concern for coasting is safety.
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You think wrongly.
Double-clutching is as relevant today as it was in 1920, and for the same reasons. But synchros now mask what failure to effectively double-clutch would have loudly and embarrassingly revealed in 1920.
Part of the reason I got 255,000 miles out of my last clutch is because I double-clutch every downshift. And after 305,000 miles my synchros work almost as well now as they did when new.
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Tegger wrote:

that bit's not true - it's because you don't slip the clutch. if anything, operating the springs/bearing twice as often as you need to /reduces/ life of the mechanical parts.

that may be true, but it's much more likely that it's because you shift more slowly as a function of the above. synchros are very effective, and provided the clutch is disengaging properly, have very little load on shifting. unless raced and slammed prematurely, synchros last as long as the rest of the transmission.
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True, but it's the engine-rev during double-clutching that keeps the clutch from slipping. I guess you could rev the engine without double-clutching, but that won't help the synchros.
If there was any additional wear on any of the parts due to double- clutching, it was undetectable when the old parts were removed. I checked specifically for that when the clutch was changed.

Let me clarify my statement: Double-clutching extends the life of the synchros far beyond what it would be if the lever had simply been dragged into each lower gear without rev-matching. It's that which kills synchros in addition to too-fast shifting.
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Tegger wrote:

it does. and that's what you should do. if you've changed gears without the clutch, you'll find it only works when the engine revs are in range.

the bits that would wear from double-clutching are the thrust bearing and the pressure plate mechanism. the friction plates won't be affected.

strictly speaking, too-fast and non-matching are the same thing. for racing, one of the reasons for lightened flywheel is that engine revs can change more quickly allowing quicker rev matching, and thus quicker shifting.
i was reminded of this a few years back when i had both a 91 stick crx and a 91 stick civic std. the std had a heavier flywheel than the crx, and the time it took for revs to drop from any given rpm was about double that of the crx with the lighter flywheel. and thus, you couldn't shift as quickly. being able to compare the two "side by side" was actually dramatic in contrast - you had to be considerably more laid back in the std.
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There was no unusual wear to any part of my clutch assembly. The pressure plate was replaced on principle because it was 255,000 miles old, not because anything was specifically wrong with it.
Riding the clutch - or neglected adjustment - will cause far quicker and more severe wear than double-clutching.
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Tegger wrote:

i didn't say there was, but by definition, the more times you operate it, the closer it gets to its limit. you're operating it twice as many times as other people, that's all.

quicker wear of the friction plate and thrust bearing, yes indeed.
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Tegger wrote:

If you knit pick, you are right. Some cars even have a shift light on the dash signalling time to shift. Tach is there for a reason. Then how many real drivers are on the road these days? Most are motor vehicle operators.
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Tegger wrote:

no dude, it's a cone clutch - cone clutches lock solid in next to no time, incur /very/ little wear, and are incredibly reliable. if you had a porsche-type baulk ring synchro, you'd be a little more correct because the wear rate is higher, but again, they last a /long/ time when everything is working right.

it's entirely unnecessary unless there's something wrong. and that "something" is usually an uncoordinated driver, or a clutch plate sticking to the flywheel. uncoordinated drivers chew up transmissions just as fast, single or double clutching.
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All synchro friction surfaces are cones. All synchros have been cones, and have operated on the same friction principles, ever since the first ones were installed in the 1928 Cadillac.
All synchro assemblies have baulk/blocker rings of some kind that prevent engagement of the dog teeth until the two synchro halves are immobile relative to each other (i.e.: matched). Baulk/blocker rings are separate from the friction surfaces of the cones, although the female half of the synchro does form one half of the baulk ring assembly. There are many, many designs of blocker rings, but all of them operate on identical principles.
If you feel the lever hang up a bit (or a lot) before dropping into gear, you are experiencing the baulk/blocker rings in action, protecting the dogs from the damage they would incur as a consequence of speed difference relative to each other. The greater the difference in friction surface rotational speeds, the more drag the synchro friction surfaces must apply before they are matched, and the longer the baulk rings will delay dog engagement. Excessive drag from excessive speed difference can actually burn through the oil film seaprating the two halves of the cone and cause metal-to-metal wear, which /dramatically/ shortens synchro life.
If the lever drops in immediately under very light pressure, the two synchro halves were closely matched in speed, and have become quickly immobile relative to each other. This means the synchros have had little work to do, and the baulk/blocker rings were not long subject to the rotational forces that caused them to prevent dog engagement.
The upshot: Proper double-clutching extends the life of the synchro friction surfaces.
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