Hard or soft braking

On 9/3/20 2:12 am, Arlen Holder wrote:
> On Sat, 7 Mar 2020 20:53:58 -0800, The Real Bev wrote:
>
>>> But that assumes putting the transmission in neutral somehow "damages" the
>>> transmission, or, getting it back in gear while coasting damages the
>>> transmission.
>>
>> Doing something different puts wear on the thing that's doing something
>> different.
>
> Maybe. Maybe not. I really do not know, and don't claim to know.
>
> My assumption is that transmissions were meant to be shifted from D to N
> and back; but that they weren't designed to do that while moving.

Transmissions will do that without complaint. What is at issue is
whether it is a good idea to be in neutral whilst on the highway. My
viewpoint is that it is not - whether the trans is a manual or an
automatic. The issue here is *safety*, not trans damage.
>
> Does doing it while moving "hurt" the transmission?
> o I don't know.

Doing it whilst moving will not, in the short term, damage the
transmission.
>
> Maybe someone here, like Xeno, knows "how" that can hurt a 2wd front or rwd
> transmission?
>


--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 9/3/20 2:12 am, Arlen Holder wrote:
> On Sun, 8 Mar 2020 12:10:24 +1100, Xeno wrote:
>
>> there is no need to shift to neutral
>> whilst stationary in traffic. The stall point on the torque converter
>> means that there will be minimal drag on the engine *at idle*.
>
> Hi Xeno,
>
> You've helped me a lot in debugging tire wear on the mountain, where I've
> informed all the neighbors of the problem set.
>
> Speaking on warranties...
>
> One of those neighbors went to Costco and kept taking advantage of the free
> rotation, but at 7,500 miles, Costco initially _refused_ to rotate the
> tires because they were _already_ worn with what we've tentatively
> concluded is "camber scrub" due, not to alignment per se, but to the
> physics of many daily low-speed tight steep turns.
>
> They talked Costco into rotating that one time by showing recent alignment
> results, but the _next_ time we expect it to happen again.
>
> I need to ask them what happened since that was a month or two ago I last
> spoke to them about it (they took all my advice on the rotation &
> alignment).
>
> As for shifting to neutral, I wonder if you know if there is any damage to
> my method (described below) for a non-four-wheel-drive, but for both a
> front-wheel drive and a rear-wheel drive?
>
> Is there?

Must ask one question here.

Why shift to neutral when going down hill? What is the benefit?
>
> Here's what I do on both the front-wheel drive & rear-wheel drive:
> a. Daily, on the downhill, I am in neutral for miles on end, where at the
> conclusion of the hill, I wait until the car is about 20mph to 30mph and
> then I match the RPM by feel and slip it into gear without lurch.
>
> b. At every opportunity for a "planned stop" (such as a red light up ahead,
> or traffic up ahead), I slip it into neutral, slow down harder than I would
> otherwise to scrub off speed, and then coast to the blockage - where the
> hope is that I can coast right through it as it clears.

Again, why the shift to neutral?
>
> c. When it's time to get back in gear, I slip it from N to D while matching
> RPM to the road speed, with the goal of eliminating all lurches.
>
> I've been doing that for years.

Please do not teach a new young learner driver to follow that practice.

The correct *slang* term for selecting neutral when coasting downhill is
*Angel's Gear*. And you may well join the angels if you continually
practice the habit.

If you think you are saving fuel, you are wrong. In the days of
carburettors, yes, fuel continued to flow through the engine, even at
the higher RPMs encountered. However, with the throttle plate closed,
even that fuel use was at a minimum since the main jets were
deactivated. With fuel injection, it's a different story. On coast
(overrun) the ECU will cut fuel injection until the engine RPM drops to
a specified minimum. Typically this is reasonably well above idle and
around 1400-1600 RPM. That means all you need to do to save fuel is
leave the trans in Drive and keep the RPM above the point where the
injectors will cut back in. And you will have engine braking as a bonus.
If you engage neutral and let the engine idle whilst coasting, you are
*still* using fuel.

What you don't have when coasting in neutral is engine braking so you
run the risk of getting brakes hotter than necessary.

If the situation changes suddenly, you have no possibly of accelerating
out of trouble *until* you re-engage Drive. That seemingly miniscule
amount of time may be the difference between avoiding an accident.

While the engine is being overrun by the transmission, the power
steering pump is still being operated. If, however, your engine stalls
out for any reason whilst in neutral, your engine RPMs will instantly
drop to zero and your power steering pump is now not pumping. That
means, on most modern vehicles, especially FWD, very heavy steering.
Here's a little scenario for you to cogitate on.

You are coasting downhill in *Angel's Gear* and, for no apparent reason,
your engine stalls. You realise this has happened because the steering
has become very heavy, the dash lights up, tach drops to zero, etc. In
these situations, *Murphy's Law* dictates that there will be a sharp
corner coming up with a rush. You slip the selector back to D for Drive.
Nothing. You select other Fwd gears, nothing. Your transmission has
become a *bag of neutrals*. You then hit the key/button and restart the
engine - except it doesn't start because - D for Drive. You realise
this, select neutral (hopefully not park), hit the key, start the
engine, then back into D for Drive. Did you get around the corner? It's
more than likely you wouldn't since, with no power steering, zippy
movements of the steering are damn difficult and it took you more time
than you realised On your seat to come to grips with what was happening.

Why did you have no selectable gears when the engine stalled out? The
answer is simple. The transmission needs oil under pressure to operate
the various servos. No oil pressure, no servos operate therefore no
clutches or bands can operate. The trans oil pump, though located in the
transmission, is actually driven by the *engine*. If the engine stops,
the pump stops, the pressure drops and the clutches and bands all
release. All neutrals.

Some people will try to tell you that the trans has another pump - no it
hasn't, they are clueless. The 2nd trans pump, which was typically
driven by the trans output shaft, disappeared in the interests of
*efficiency* some 50-60 years ago, nor was it particularly ubiquitous.
The old 2 speed Ford transmission had one - How far back were they?

You can try the above exercise for yourself. Please do select a straight
stretch of downhill empty road to experiment on.

I might note, selecting neutral and coasting downhills is *illegal* in
Australia. The reasoning being that you are *not in control* of the
vehicle. If something jumps out in front of you, reaction times dictates
that you may not have sufficient time to re-engage Drive and take
evasive action. In fact, the most likely scenario is that you will hit
the accelerator or brake first, then try to evade the situation by
accelerating. You will have momentarily forgotten you are in *Angel's
Gear* and it might well be fatal. Sudden panic does that to your memory.

>
> Dunno if it hurts the transmission or not though, as there's not much value
> in a study of just one.
>
There is no value in selecting neutral and coasting down hills but a lot
of risk.

There is no value in selecting neutral when stopped at traffic lights.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On Mon, 9 Mar 2020 17:38:35 +1100, Xeno wrote:

> Transmissions will do that without complaint. What is at issue is
> whether it is a good idea to be in neutral whilst on the highway. My
> viewpoint is that it is not - whether the trans is a manual or an
> automatic. The issue here is *safety*, not trans damage.

Hi Xeno,
I very much appreciate your technical acumen.

I would like to ask that we ignore the "danger" factor to humans, as that
isn't my technical question in the least.

You've made your point on the "danger factor" so that _others_ will be
scared enough to have second thoughts - but the "danger factor" isn't even
on my list of the least of my worries (I've explained why in the other
post).

My key _technical_ question I would love to know the answer of is this:
Q: *Does constant daily prolonged engine braking cause transmission wear*?
--
Together we can learn far more than anyone of us can by learning alone.

On Mon, 9 Mar 2020 19:41:21 +1100, Xeno wrote:

> Must ask one question here.
> Why shift to neutral when going down hill? What is the benefit?

Hi Xeno,

What I need help in understanding is the simple answer to the question:
Q: *Does constant daily prolonged engine braking cause transmission wear*?

I appreciate your advice as you know transmissions better than I do.
o The main point is to minimize _wear_ on the transmission - with finesse.

Nothing else matters to me as I've _already_ taken it all into account.
o The _only_ real unknown is whether I'm saving wear on the transmission.

That's where I need your technical advice most:
a. Does _not_ engine braking (for miles and miles every single day) save
wear on the transmission?

As for brake-system braking, I fully understand your question, where we
have to remember the fact there is absolutely zero chance of not braking at
every curve. Zero. With or without engine braking.

So you're gonna brake like hell, no matter what.

The second point is that an automatic doesn't do all that much engine
braking, so, you're _still_ gonna brake "about as much" with or without
engine braking (although certainly you'll be braking a bit more).

Third point is that engine braking itself, "may" contribute to transmission
wear, whereas traveling in neutral "might not", as long as we assume that
the transmission isn't spinning and if it is, then it's getting the oil it
needs (e.g., when towing, I believe that's an issue, is it not?).

Fourth point is that the gas mileage will be better (slightly) without the
engine braking, which, since it raises RPM, raises fuel consumption (only
slightly, of course). [EDIT: I just saw your fuel injection info below.]

The fifth point is that eventually, at the bottom of the hill, miles later,
you do have to match the RPM when you finally put it in gear, which "can"
perhaps damage the transmission over time.

Add all five points up, and I don't see how engine braking "helps" protect
wear on brakes, where replacing brakes is trivial compared to replacing
transmissions, so as long as coasting down a hill does not damage a
transmission, then coasting down a hill saves on gas mileage and
transmission wear (all things added up).

The key question in that calculation, of course, is whether or not there is
damage to the transmission from these key factors:
o Coasting for miles at low speeds (~20 to 25mph) in neutral
o Engine braking damage to the transmission by _not_ coasting in neutral
o Shifting into N at the start & then into D at matched RPM at the bottom

The potential benefits are clearly obvious - if admittedly rather slight.
o The key question is whether any "damage" occurs to the transmission.

Is there?

> Again, why the shift to neutral?

As explained above, it's a logically inspired tradeoff by the "theory" that
it's better to shift wear from the transmission (due to constant engine
braking) to the brakes.

It's also (admittedly slight) an improvement in gasoline efficiency.
o And, in fact, truth be told, it's kind of fun to use "potential energy".

The math works out wonderfully, if admittedly slight, only if there's no
additional damage to the transmission incurred by coasting for miles in
neutral on a steep downslope at low speeds.

I'd even turn the engine off, if I could, but of course, then there's be no
power brakes or power steering, so the engine must idle the entire way
while we're otherwise on 100% potential energy the entire fun trip!

> Please do not teach a new young learner driver to follow that practice.

I teach the kids "finesse", e.g., to slow down well before a stop, so that
they don't leave a pad imprint on the rotor (which can build up over time
and cause DTV (disc thickness variation) vibrations).

I also teach the kids "finesse" in turn signaling (it's not for the cars
you see - but for the cars you don't see); and I teach them finesse in
shifting in a manual (revs into the power band are your friend); and I
teach them finesse in turning (always take the lane nearest you so that the
car you don't see has room to get around you); etc.

I teach them finesse such as understanding how US Interstate road signs
work (i.e., in a single mile in any Interstate in the USA, you can tell
both what direction you're going and how far it is to your exit and how far
to the end of the road in one direction, and what other Interstate the
Interstate you're on connects to, etc.).

I teach them emergency actions, such as interpretation of the slanted
yellow and black signs (almost nobody knows which "direction" they go but I
teach the kids the proper direction); and I teach them how to pump the
brakes in an emergency (although admittedly, some of the cars I'm teaching
them on have ABS).

> The correct *slang* term for selecting neutral when coasting downhill is
> *Angel's Gear*. And you may well join the angels if you continually
> practice the habit.

Remember, this is a road where, on a Sunday, for example, no cars will go
up or down for an entire day (I've hiked the entire road many times, miles
and miles, and there were no cars).

The fact is that you'll _never_ need to hit the gas. You just won't.

We're not talking a divided highway with other traffic, both ways, and
turnoffs.

This is a windy mountain road that has almost zero traffic on it, where the
ONLY thing you'll EVER need to do, is brake.

I can't even imagine a situation where you'll need to accelerate.

> If you think you are saving fuel, you are wrong. In the days of
> carburettors, yes, fuel continued to flow through the engine, even at
> the higher RPMs encountered. However, with the throttle plate closed,
> even that fuel use was at a minimum since the main jets were
> deactivated.

Hmmmm..... this is GOOD information.
o All these vehicles are fuel injected.

> With fuel injection, it's a different story. On coast
> (overrun) the ECU will cut fuel injection until the engine RPM drops to
> a specified minimum. Typically this is reasonably well above idle and
> around 1400-1600 RPM.

Hmmmmm... that's double idle speed.
o I don't see how the _engine_ braking won't control the RPM

Each RPM has an injection cycle into the intake manifold, doesn't it?

> That means all you need to do to save fuel is
> leave the trans in Drive and keep the RPM above the point where the
> injectors will cut back in.

I don't understand.
o Doesn't each RPM have its own fuel injection cycle into the manifold?

I equate RPM with gasoline used (even if the throttle plate is closed).
o Is that wrong?

> And you will have engine braking as a bonus.

But engine braking "may" also translate to "wear" on the transmission.
o All that force has to go somewhere.

> If you engage neutral and let the engine idle whilst coasting, you are
> *still* using fuel.

Of course.
o But you're at 700 RPM with zero load on the engine.

> What you don't have when coasting in neutral is engine braking so you
> run the risk of getting brakes hotter than necessary.

While this is "technical" and fundamentally true, I doubt it matters.
o There's absolutely zero chance you're not braking under all condistions.

You're just braking less while engine braking.
o Where you're trading, I assume, transmission wear for brake wear.

Given _that_ tradeoff, I'll take brake wear any day over transmission wear.
o Hence, the entire argument boils down, fundamentally, to one question:

Fundamental technical question:
Q: *Does engine braking cause wear on the transmission, or not*?

> If the situation changes suddenly, you have no possibly of accelerating
> out of trouble *until* you re-engage Drive. That seemingly miniscule
> amount of time may be the difference between avoiding an accident.

Not gonna happen.
o Not on these roads.

I can't say there's zero chance, but, I can't even _imagine_ a situation on
these roads where you'll need to accelerate out of a problem.

I guess, thinking hard, a tree could be falling in front of you where you
decide it's better to accelerate past it (and crash on the other side of
the curve instead of being crushed by the tree) but, in reality, the chance
of needing to accelerate on these untraveled roads, is nearly zero.

I don't want you to think I'm dismissing out of hand your concern, where
I'm well aware it's illegal to ever be in neutral for _that_ reason; but
it's like owning a chainsaw or working on brakes - you have to be able to
assess the risk where that risk I dismiss out of hand on these roads.

The only reason _not_ to do this would be if there's some other
disadvantage, such as if it's actually _causing_ wear to the transmission
instead of the goal, which is to _prevent_ wear to the transmission.

> While the engine is being overrun by the transmission, the power
> steering pump is still being operated. If, however, your engine stalls
> out for any reason whilst in neutral, your engine RPMs will instantly
> drop to zero and your power steering pump is now not pumping. That
> means, on most modern vehicles, especially FWD, very heavy steering.
> Here's a little scenario for you to cogitate on.

I'm not worried about loss of power steering, Xeno.
o I may as well worry that my tires are gonna blow up in my face when I
mount them.

Sure, it "can" happen; but to worry that much about something so remote
that is easily recovered from, I'm just not gonna worry about that.

If that's the _only_ reason to not do it, then there's no good reason not
to do it.

The main concern I have, which is a _technical_ concern, is whether or not
I'm saving damage to the transmission by not using it for engine braking.

With all due respect on your technical acumen, _that_ is where I need your
advice most.

> I might note, selecting neutral and coasting downhills is *illegal* in
> Australia. The reasoning being that you are *not in control* of the
> vehicle.

Yup. Just like using a chainsaw is dangerous but effective, I am not in the
least worried about the law in this case. I understand the law.

What I need help in understanding is the simple answer to the question:
Q: Is constant daily prolonged engine braking causing transmission wear?

> There is no value in selecting neutral and coasting down hills but a lot
> of risk.

I've assessed the risk; what I need to know is the "technical" stuff.
Q: Does constant daily prolonged engine braking cause transmission wear?

> There is no value in selecting neutral when stopped at traffic lights.

The technical question is whether or not wear occurs due to constant
incessant repeated daily prolonged ever-present engine braking?
--
Together we can learn far more than anyone of us can by learning alone.

Xeno wrote:
> On 9/3/20 2:12 am, Arlen Holder wrote:
>> On Sun, 8 Mar 2020 12:10:24 +1100, Xeno wrote:
>>
>>> there is no need to shift to neutral
>>> whilst stationary in traffic. The stall point on the torque converter
>>> means that there will be minimal drag on the engine *at idle*.
>> Hi Xeno,
>>
>> You've helped me a lot in debugging tire wear on the mountain, where I've
>> informed all the neighbors of the problem set.
>>
>> Speaking on warranties...
>>
>> One of those neighbors went to Costco and kept taking advantage of the free
>> rotation, but at 7,500 miles, Costco initially _refused_ to rotate the
>> tires because they were _already_ worn with what we've tentatively
>> concluded is "camber scrub" due, not to alignment per se, but to the
>> physics of many daily low-speed tight steep turns.
>>
>> They talked Costco into rotating that one time by showing recent alignment
>> results, but the _next_ time we expect it to happen again.
>>
>> I need to ask them what happened since that was a month or two ago I last
>> spoke to them about it (they took all my advice on the rotation &
>> alignment).
>>
>> As for shifting to neutral, I wonder if you know if there is any damage to
>> my method (described below) for a non-four-wheel-drive, but for both a
>> front-wheel drive and a rear-wheel drive?
>>
>> Is there?
>
> Must ask one question here.
>
> Why shift to neutral when going down hill? What is the benefit?
>> Here's what I do on both the front-wheel drive & rear-wheel drive:
>> a. Daily, on the downhill, I am in neutral for miles on end, where at the
>> conclusion of the hill, I wait until the car is about 20mph to 30mph and
>> then I match the RPM by feel and slip it into gear without lurch.
>>
>> b. At every opportunity for a "planned stop" (such as a red light up ahead,
>> or traffic up ahead), I slip it into neutral, slow down harder than I would
>> otherwise to scrub off speed, and then coast to the blockage - where the
>> hope is that I can coast right through it as it clears.
>
> Again, why the shift to neutral?
>> c. When it's time to get back in gear, I slip it from N to D while matching
>> RPM to the road speed, with the goal of eliminating all lurches.
>>
>> I've been doing that for years.
>
> Please do not teach a new young learner driver to follow that practice.
>
> The correct *slang* term for selecting neutral when coasting downhill is
> *Angel's Gear*. And you may well join the angels if you continually
> practice the habit.
>
> If you think you are saving fuel, you are wrong. In the days of
> carburettors, yes, fuel continued to flow through the engine, even at
> the higher RPMs encountered. However, with the throttle plate closed,
> even that fuel use was at a minimum since the main jets were
> deactivated. With fuel injection, it's a different story. On coast
> (overrun) the ECU will cut fuel injection until the engine RPM drops to
> a specified minimum. Typically this is reasonably well above idle and
> around 1400-1600 RPM. That means all you need to do to save fuel is
> leave the trans in Drive and keep the RPM above the point where the
> injectors will cut back in. And you will have engine braking as a bonus.
> If you engage neutral and let the engine idle whilst coasting, you are
> *still* using fuel.
>
> What you don't have when coasting in neutral is engine braking so you
> run the risk of getting brakes hotter than necessary.
>
> If the situation changes suddenly, you have no possibly of accelerating
> out of trouble *until* you re-engage Drive. That seemingly miniscule
> amount of time may be the difference between avoiding an accident.
>
> While the engine is being overrun by the transmission, the power
> steering pump is still being operated. If, however, your engine stalls
> out for any reason whilst in neutral, your engine RPMs will instantly
> drop to zero and your power steering pump is now not pumping. That
> means, on most modern vehicles, especially FWD, very heavy steering.
> Here's a little scenario for you to cogitate on.
>
> You are coasting downhill in *Angel's Gear* and, for no apparent reason,
> your engine stalls. You realise this has happened because the steering
> has become very heavy, the dash lights up, tach drops to zero, etc. In
> these situations, *Murphy's Law* dictates that there will be a sharp
> corner coming up with a rush. You slip the selector back to D for Drive.
> Nothing. You select other Fwd gears, nothing. Your transmission has
> become a *bag of neutrals*. You then hit the key/button and restart the
> engine - except it doesn't start because - D for Drive. You realise
> this, select neutral (hopefully not park), hit the key, start the
> engine, then back into D for Drive. Did you get around the corner? It's
> more than likely you wouldn't since, with no power steering, zippy
> movements of the steering are damn difficult and it took you more time
> than you realised On your seat to come to grips with what was happening.
>
> Why did you have no selectable gears when the engine stalled out? The
> answer is simple. The transmission needs oil under pressure to operate
> the various servos. No oil pressure, no servos operate therefore no
> clutches or bands can operate. The trans oil pump, though located in the
> transmission, is actually driven by the *engine*. If the engine stops,
> the pump stops, the pressure drops and the clutches and bands all
> release. All neutrals.
>
> Some people will try to tell you that the trans has another pump - no it
> hasn't, they are clueless. The 2nd trans pump, which was typically
> driven by the trans output shaft, disappeared in the interests of
> *efficiency* some 50-60 years ago, nor was it particularly ubiquitous.
> The old 2 speed Ford transmission had one - How far back were they?
>
> You can try the above exercise for yourself. Please do select a straight
> stretch of downhill empty road to experiment on.
>
> I might note, selecting neutral and coasting downhills is *illegal* in
> Australia. The reasoning being that you are *not in control* of the
> vehicle. If something jumps out in front of you, reaction times dictates
> that you may not have sufficient time to re-engage Drive and take
> evasive action. In fact, the most likely scenario is that you will hit
> the accelerator or brake first, then try to evade the situation by
> accelerating. You will have momentarily forgotten you are in *Angel's
> Gear* and it might well be fatal. Sudden panic does that to your memory.
>
>> Dunno if it hurts the transmission or not though, as there's not much value
>> in a study of just one.
>>
> There is no value in selecting neutral and coasting down hills but a lot
> of risk.
>
> There is no value in selecting neutral when stopped at traffic lights.
>

It's illegal in many US states for the same reason.


--
Steve W.

Arlen Holder > wrote:
> On Mon, 9 Mar 2020 17:38:35 +1100, Xeno wrote:
>
>> Transmissions will do that without complaint. What is at issue is
>> whether it is a good idea to be in neutral whilst on the highway. My
>> viewpoint is that it is not - whether the trans is a manual or an
>> automatic. The issue here is *safety*, not trans damage.
>
> Hi Xeno,
> I very much appreciate your technical acumen.
>
> I would like to ask that we ignore the "danger" factor to humans, as that
> isn't my technical question in the least.
>
> You've made your point on the "danger factor" so that _others_ will be
> scared enough to have second thoughts - but the "danger factor" isn't even
> on my list of the least of my worries (I've explained why in the other
> post).
>
> My key _technical_ question I would love to know the answer of is this:
> Q: *Does constant daily prolonged engine braking cause transmission wear*?

Short answer; no.

Xeno

On Mon, 09 Mar 2020 15:15:14 -0400, Steve W. wrote:

>> There is no value in selecting neutral when stopped at traffic lights.
>>
>
> It's illegal in many US states for the same reason.

There is value in _not_ imprinting the pad footprint on a hot rotor.
o How you go about _not_ depositing the footprint is what we can debate.
--
Factual information allows you to make more intelligent adult decisions.

On 9 Mar 2020 22:59:47 GMT, Xeno wrote:

>> My key _technical_ question I would love to know the answer of is this:
>> Q: *Does constant daily prolonged engine braking cause transmission wear*?
>
> Short answer; no.

Then that makes the decision rather easy.
o Daily incessant constant slow-speed engine braking for miles on end;
o ... or ... Daily incessant brake-system braking for miles on end.

There's no danger either way given acceleration on this road is almost
impossible to fathom (as you'd run off the road if you accelerated).
<https://i.postimg.cc/kGhZh80q/mount44.jpg>

You're going to be constantly "braking" either way given the facts:
<https://i.postimg.cc/pX44ffQB/mount46.jpg>
--
Usenet is so much more valuable, and pleasant, when people act like adults.

On 10/3/20 10:58 am, Arlen Holder wrote:
> On 9 Mar 2020 22:59:47 GMT, Xeno wrote:
>
>>> My key _technical_ question I would love to know the answer of is this:
>>> Q: *Does constant daily prolonged engine braking cause transmission wear*?
>>
>> Short answer; no.
>
> Then that makes the decision rather easy.
> o Daily incessant constant slow-speed engine braking for miles on end;
> o ... or ... Daily incessant brake-system braking for miles on end.
>
> There's no danger either way given acceleration on this road is almost
> impossible to fathom (as you'd run off the road if you accelerated).
> <https://i.postimg.cc/kGhZh80q/mount44.jpg>
>
> You're going to be constantly "braking" either way given the facts:
> <https://i.postimg.cc/pX44ffQB/mount46.jpg>
>
The trans is better able to dissipate heat than the brakes under low
speed decel.

Also, on your road, I wouldn't be on the brakes much at all. I would
just manually select an appropriate lower gear. I like to preserve the
brakes as much as possible and the trans is designed with ablative
technologies in mind.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 10/3/20 3:36 am, Arlen Holder wrote:
> On Mon, 9 Mar 2020 19:41:21 +1100, Xeno wrote:
>
>> Must ask one question here.
>> Why shift to neutral when going down hill? What is the benefit?
>
> Hi Xeno,
>
> What I need help in understanding is the simple answer to the question:
> Q: *Does constant daily prolonged engine braking cause transmission wear*?
>
> I appreciate your advice as you know transmissions better than I do.
> o The main point is to minimize _wear_ on the transmission - with finesse.
>
> Nothing else matters to me as I've _already_ taken it all into account.
> o The _only_ real unknown is whether I'm saving wear on the transmission.
>
> That's where I need your technical advice most:
> a. Does _not_ engine braking (for miles and miles every single day) save
> wear on the transmission?
>
> As for brake-system braking, I fully understand your question, where we
> have to remember the fact there is absolutely zero chance of not braking at
> every curve. Zero. With or without engine braking.
>
> So you're gonna brake like hell, no matter what.
>
> The second point is that an automatic doesn't do all that much engine
> braking, so, you're _still_ gonna brake "about as much" with or without
> engine braking (although certainly you'll be braking a bit more).
>
> Third point is that engine braking itself, "may" contribute to transmission
> wear, whereas traveling in neutral "might not", as long as we assume that
> the transmission isn't spinning and if it is, then it's getting the oil it
> needs (e.g., when towing, I believe that's an issue, is it not?).
>
> Fourth point is that the gas mileage will be better (slightly) without the
> engine braking, which, since it raises RPM, raises fuel consumption (only
> slightly, of course). [EDIT: I just saw your fuel injection info below.]
>
> The fifth point is that eventually, at the bottom of the hill, miles later,
> you do have to match the RPM when you finally put it in gear, which "can"
> perhaps damage the transmission over time.
>
> Add all five points up, and I don't see how engine braking "helps" protect
> wear on brakes, where replacing brakes is trivial compared to replacing
> transmissions, so as long as coasting down a hill does not damage a
> transmission, then coasting down a hill saves on gas mileage and
> transmission wear (all things added up).
>
> The key question in that calculation, of course, is whether or not there is
> damage to the transmission from these key factors:
> o Coasting for miles at low speeds (~20 to 25mph) in neutral
> o Engine braking damage to the transmission by _not_ coasting in neutral
> o Shifting into N at the start & then into D at matched RPM at the bottom
>
> The potential benefits are clearly obvious - if admittedly rather slight.
> o The key question is whether any "damage" occurs to the transmission.
>
> Is there?
>
>> Again, why the shift to neutral?
>
> As explained above, it's a logically inspired tradeoff by the "theory" that
> it's better to shift wear from the transmission (due to constant engine
> braking) to the brakes.
>
> It's also (admittedly slight) an improvement in gasoline efficiency.
> o And, in fact, truth be told, it's kind of fun to use "potential energy".
>
> The math works out wonderfully, if admittedly slight, only if there's no
> additional damage to the transmission incurred by coasting for miles in
> neutral on a steep downslope at low speeds.
>
> I'd even turn the engine off, if I could, but of course, then there's be no
> power brakes or power steering, so the engine must idle the entire way
> while we're otherwise on 100% potential energy the entire fun trip!
>
>> Please do not teach a new young learner driver to follow that practice.
>
> I teach the kids "finesse", e.g., to slow down well before a stop, so that
> they don't leave a pad imprint on the rotor (which can build up over time
> and cause DTV (disc thickness variation) vibrations).
>
> I also teach the kids "finesse" in turn signaling (it's not for the cars
> you see - but for the cars you don't see); and I teach them finesse in
> shifting in a manual (revs into the power band are your friend); and I
> teach them finesse in turning (always take the lane nearest you so that the
> car you don't see has room to get around you); etc.
>
> I teach them finesse such as understanding how US Interstate road signs
> work (i.e., in a single mile in any Interstate in the USA, you can tell
> both what direction you're going and how far it is to your exit and how far
> to the end of the road in one direction, and what other Interstate the
> Interstate you're on connects to, etc.).
>
> I teach them emergency actions, such as interpretation of the slanted
> yellow and black signs (almost nobody knows which "direction" they go but I
> teach the kids the proper direction); and I teach them how to pump the
> brakes in an emergency (although admittedly, some of the cars I'm teaching
> them on have ABS).
>
>> The correct *slang* term for selecting neutral when coasting downhill is
>> *Angel's Gear*. And you may well join the angels if you continually
>> practice the habit.
>
> Remember, this is a road where, on a Sunday, for example, no cars will go
> up or down for an entire day (I've hiked the entire road many times, miles
> and miles, and there were no cars).
>
> The fact is that you'll _never_ need to hit the gas. You just won't.
>
> We're not talking a divided highway with other traffic, both ways, and
> turnoffs.
>
> This is a windy mountain road that has almost zero traffic on it, where the
> ONLY thing you'll EVER need to do, is brake.
>
> I can't even imagine a situation where you'll need to accelerate.
>
>> If you think you are saving fuel, you are wrong. In the days of
>> carburettors, yes, fuel continued to flow through the engine, even at
>> the higher RPMs encountered. However, with the throttle plate closed,
>> even that fuel use was at a minimum since the main jets were
>> deactivated.
>
> Hmmmm..... this is GOOD information.
> o All these vehicles are fuel injected.
>
>> With fuel injection, it's a different story. On coast
>> (overrun) the ECU will cut fuel injection until the engine RPM drops to
>> a specified minimum. Typically this is reasonably well above idle and
>> around 1400-1600 RPM.
>
> Hmmmmm... that's double idle speed.
> o I don't see how the _engine_ braking won't control the RPM
>
> Each RPM has an injection cycle into the intake manifold, doesn't it?
>
>> That means all you need to do to save fuel is
>> leave the trans in Drive and keep the RPM above the point where the
>> injectors will cut back in.
>
> I don't understand.
> o Doesn't each RPM have its own fuel injection cycle into the manifold?
>
> I equate RPM with gasoline used (even if the throttle plate is closed).
> o Is that wrong?
>
>> And you will have engine braking as a bonus.
>
> But engine braking "may" also translate to "wear" on the transmission.
> o All that force has to go somewhere.
>
>> If you engage neutral and let the engine idle whilst coasting, you are
>> *still* using fuel.
>
> Of course.
> o But you're at 700 RPM with zero load on the engine.
>
>> What you don't have when coasting in neutral is engine braking so you
>> run the risk of getting brakes hotter than necessary.
>
> While this is "technical" and fundamentally true, I doubt it matters.
> o There's absolutely zero chance you're not braking under all condistions.
>
> You're just braking less while engine braking.
> o Where you're trading, I assume, transmission wear for brake wear.
>
> Given _that_ tradeoff, I'll take brake wear any day over transmission wear.
> o Hence, the entire argument boils down, fundamentally, to one question:
>
> Fundamental technical question:
> Q: *Does engine braking cause wear on the transmission, or not*?
>
>> If the situation changes suddenly, you have no possibly of accelerating
>> out of trouble *until* you re-engage Drive. That seemingly miniscule
>> amount of time may be the difference between avoiding an accident.
>
> Not gonna happen.
> o Not on these roads.
>
> I can't say there's zero chance, but, I can't even _imagine_ a situation on
> these roads where you'll need to accelerate out of a problem.
>
> I guess, thinking hard, a tree could be falling in front of you where you
> decide it's better to accelerate past it (and crash on the other side of
> the curve instead of being crushed by the tree) but, in reality, the chance
> of needing to accelerate on these untraveled roads, is nearly zero.
>
> I don't want you to think I'm dismissing out of hand your concern, where
> I'm well aware it's illegal to ever be in neutral for _that_ reason; but
> it's like owning a chainsaw or working on brakes - you have to be able to
> assess the risk where that risk I dismiss out of hand on these roads.
>
> The only reason _not_ to do this would be if there's some other
> disadvantage, such as if it's actually _causing_ wear to the transmission
> instead of the goal, which is to _prevent_ wear to the transmission.
>
>> While the engine is being overrun by the transmission, the power
>> steering pump is still being operated. If, however, your engine stalls
>> out for any reason whilst in neutral, your engine RPMs will instantly
>> drop to zero and your power steering pump is now not pumping. That
>> means, on most modern vehicles, especially FWD, very heavy steering.
>> Here's a little scenario for you to cogitate on.
>
> I'm not worried about loss of power steering, Xeno.
> o I may as well worry that my tires are gonna blow up in my face when I
> mount them.
>
> Sure, it "can" happen; but to worry that much about something so remote
> that is easily recovered from, I'm just not gonna worry about that.
>
> If that's the _only_ reason to not do it, then there's no good reason not
> to do it.
>
> The main concern I have, which is a _technical_ concern, is whether or not
> I'm saving damage to the transmission by not using it for engine braking.

As far as gear wear is concerned, in the overrun you are using the coast
(back) side of the gear teeth so the relatively *unworn* part. As well,
one single full throttle acceleration would apply the wear of a thousand
engine braking instances. Under acceleration, you are applying the *full
power* of the engine. Under engine braking you are only applying
friction and engine pumping losses. If you are concerned about
transmission wear, it's not engine braking you should be concerned about
as most wear occurs under acceleration.
>
> With all due respect on your technical acumen, _that_ is where I need your
> advice most.
>
>> I might note, selecting neutral and coasting downhills is *illegal* in
>> Australia. The reasoning being that you are *not in control* of the
>> vehicle.
>
> Yup. Just like using a chainsaw is dangerous but effective, I am not in the
> least worried about the law in this case. I understand the law.

That works until **** happens.
>
> What I need help in understanding is the simple answer to the question:
> Q: Is constant daily prolonged engine braking causing transmission wear?

No
>
>> There is no value in selecting neutral and coasting down hills but a lot
>> of risk.
>
> I've assessed the risk; what I need to know is the "technical" stuff.
> Q: Does constant daily prolonged engine braking cause transmission wear?

No
>
>> There is no value in selecting neutral when stopped at traffic lights.
>
> The technical question is whether or not wear occurs due to constant
> incessant repeated daily prolonged ever-present engine braking?

No
> --
> Together we can learn far more than anyone of us can by learning alone.
>


--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)