Is it safe to down-shift auto-trany??
Tiger
I typically down-shift when approaching traffic lights, or when exiting the
freeway, and thereby use "engine braking" to aid in slowing down.
Will the transmission be damaged if I regulary down-shift???
Thanks,
Mike
Herb Kauhry
downshifting use?
--
"Tiger" <Mike...@cfl.rr.com> wrote in message
news:4WXec.423030$B81.6...@twister.tampabay.rr.com...
SizzleMP
>the
>> freeway, and thereby use "engine braking" to aid in slowing down.
>>
>> Will the transmission be damaged if I regulary down-shift???
>>
You should only downhift if you are going up or going down a steep grade.
Downshifting just to stop under normal driving is a waste and putting extra
strain on the tranny and engine.
Steve G
the same amount of load under acceleration. By that I mean if you take the
amount of braking "sensation" you can get by the engine and turn that around
into an equal acceleration "sensation" the load is the same. Looking at it
like that, the engine load under de-cel is equal to a very light foot on the
throttle leaving a stop light. Same goes for the transmission. In fact
there are provisions in transmissions specifically to accommodate engine
braking. Not familiar with internals on Explorer trans, but all older GM
trans when run in " drive", run in 1st and 2nd gear through a one way
clutch, meaning they free wheel in deceleration (this improves upshift times
as no clutch or band has to disconnect to move to the next upward gear.
When you manually select 2nd gear a band is applied to give you engine
braking. This is all by design.
About the only thing that can be said as a neg for downshifting is that
each time a gear change occurs a clutch pack or band has to engage or
dis-engage. It is this action that causes wear and heat in the clutch or
band. Once a band or clutch is applied or released there is no movement of
one component relative to another and so no wear occurs. So, if you're
increasing the number of times clutches and bands apply and release you are
accelerating the wear in these components. Having said that though.
transmissions seldom fail from worn out clutches or bands like this. It is
primarily internal leakage that results in their failure, seals on the
pistons that apply the clutches and bands or someone getting stuck and
continually going back and forth between forward and reverse that burns out
a clutch pack and/or overheats the trans.
Steve
"SizzleMP" <sizz...@aol.com> wrote in message
news:20040414075508...@mb-m11.aol.com...
Bill Funk
wrote:
Safe? If you mean for the tranny, yes.
If you mean, is it a safe method of controlling your speed, then my
opinion is this: It's better to use the brakes.
This is what brakes are designed for, and using tyhe brakes means your
foot is already *on* the brake pedal. This can be critical if the
idjit in front of you decides to stop faster than your tranny can
provide; the extra reaction/foot movement time can be critical.
Overall, the saved wear on the brakes is not going to be noticed, and
the tranny doesn't need the extra wear that the clutchpacks will get
doing this.
--
Bill Funk
replace "g" with "a"
pray4surf
news:3euq70dmufoqhq61k...@4ax.com...
: On Tue, 13 Apr 2004 20:18:08 GMT, "Tiger" <Mike...@cfl.rr.com>
Downshifting out of an OD gear is handy when one is descending a steep grade
or when one is ascending a grade and helps to keep the tranny from
'hunting' between the OD gear and the next 'lower' gear...
YMMV
Rick
AZGuy
wrote:
>'91 EB 4x4 Explorer w/Automatic Trany
I doubt it will be "damaged" but I suspect it will experience more
wear. Will it be enough to matter? I don't know. I do know that I'd
much rather replace my brakes then have my transmission rebuilt.
Downshifting as you describe seems rather pointless to me but the way
I accelerate seems pointless to others so don't take it as a
criticism.
--
Elbridge Gerry, of Massachusetts:
"What, sir, is the use of militia? It is to prevent the
establishment of a standing army, the bane of liberty. . .
Whenever Government means to invade the rights and liberties of
the people, they always attempt to destroy the militia, in order
to raise a standing army upon its ruins." -- Debate, U.S. House
of Representatives, August 17, 1789
Mike
transmissions. Also, I would think the rear brakes would be more
susceptable to locking up if it were wet or slippery during braking &
downshifting.
Mike
"Tiger" <Mike...@cfl.rr.com> wrote in message news:<4WXec.423030$B81.6...@twister.tampabay.rr.com>...
Herb Kauhry
Another important factor is you don't display brake lights to the guy behind
you when you slow down via downshift. This could be bad for you and your
bumpers.
--
"Mike" <mb...@frontiernet.net> wrote in message
news:d8abd1d9.04041...@posting.google.com...
Bill Funk
wrote:
From the OP:"I typically down-shift when approaching traffic lights,
or when exiting the freeway, and thereby use "engine braking" to aid
in slowing down."
Yes, I take the tranny out of DO sometimes on downgrades; it's a
recommended practice.
I don't find this necessary on upgrades, though, as neither our 92
Sport nor our 99 Expedition will hunt going uphill. Neither did any of
our other OD equipped autos. But that's us.
Tiger
and I've even been able to answer a few questions which have helped those
who posted them.
I have an old '91 EB with a recently re-built trany and an old habit of
down-shifting left over from many years of owning a standard shift 5-speed
sport car. Several months after the re-built trany was installed I began
to notice a very slight noise coming from the trany as it drops into OD
during normal driving. On a hunch, I stopped down shifting, and the noise
has slowly faded.
Is this pure coincidence, or is there some connection which I'm un-aware of.
This is the reason for my post.
Mike
<Alan Moo...@visi.com> wrote in message
news:prc180hrovlifp58t...@4ax.com...
> On Wed, 14 Apr 2004 13:55:21 GMT, "Steve G"
> <Nospamf...@Steve-Garner.com> wrote:
>
> >That's nonsense. Engine braking causes no more strain on the engine then
> >the same amount of load under acceleration. By that I mean if you take
the
> >amount of braking "sensation" you can get by the engine and turn that
around
> >into an equal acceleration "sensation" the load is the same. Looking at
it
> >like that, the engine load under de-cel is equal to a very light foot on
the
> >throttle leaving a stop light. Same goes for the transmission. In fact
> >there are provisions in transmissions specifically to accommodate engine
> >braking.
>
> Well, the force may not be too great, but you have just REVERSED the
> normal flow of force through the engine and the transmission.
>
> While they are designed to handle that, to a degree, it isn't
> something you should do on a whim.
>
> Actually, I can't believe we're all taking that original poster
> seriously! Have you heard of a troll?
>
>
>
Bill Funk
wrote:
>Well, Alan, I'm not a troll. I've posted here numerous times in the past,
>and I've even been able to answer a few questions which have helped those
>who posted them.
>
>I have an old '91 EB with a recently re-built trany and an old habit of
>down-shifting left over from many years of owning a standard shift 5-speed
>sport car. Several months after the re-built trany was installed I began
>to notice a very slight noise coming from the trany as it drops into OD
>during normal driving. On a hunch, I stopped down shifting, and the noise
>has slowly faded.
>
>Is this pure coincidence, or is there some connection which I'm un-aware of.
>This is the reason for my post.
>
>Mike
Everytime auto trannies shift, they wear. Whether the shift is up or
down, they wear.
Auto makers recommend that you leave a modern auto OD tranny in OD
unless the tranny starts to 'hunt', in which case you take it out of
OD.
That said, on long downhills, downshifting can save wear on the
brakes, while helping you to maintain a safe speed. The single
downshift isn't causing much wear, and the engine braking saves wear
on the brakes. *In theory*, the other drivers will be able to
understand what's going on.
In traffic, though, another consideration comes into play; many
drivers really aren't paying much attention to what's going on around
them, and will actually miss the fact that the vehicle in front of
them is slowing down without those bright red lights to bring it to
their attention. In this situation, I use the brakes instead of
downshifting; it helps the other drivers keep from buying the back of
my vehicle. It also reduces the wear on the tranny.
Without actually knowing what's going on in *your* tranny, it gets
hard to diagnose it. General rules tend to break down when we attempt
to apply them to individual units. (This is one reason why Jim's
replies can be rather long; he does a good job of trying to cover all
bases.)
sf/gf
I have two thoughts on this subject. First, remember the old saying,
"brakes are cheaper to replace than transmissions".
Secondly, I too am of the old school and frequently downshift, depending on
traffic, while coming to a stop, but only when I am driving a manual
transmission. For an auto trans, I usually leave the transmission in 2
while in the city in congested traffic (where speed does not get above 40
mph). This results in two benefits. One, the transmission starts in 2 and
never shifts out of 2, resulting in less wear. Two, you get some engine
braking, which results in less brake wear. The amount of engine braking (or
compression braking) does not seem to be enough so that I am in danger of
being rear ended by another driver, but Bill Funk has a point!
The only disadvantage to leaving it in 2 seems to be somewhat of a loss in
power or acceleration due to starting in 2 instead of first gear, and also
perhaps some increase in fuel use. However my rpm's never get above 2700
while leaving it in 2 in congested traffic, so I think the increased fuel
use is minimal.
Steve
Steve G
sluggish feel when starting off in second gear means the torque converter
has to do much more of that, convert torque. This is where almost all of
the heat in an auto trans is generated. Once the bands are tightened or the
clutches applied there is no slippage and thus no heat generated. Heat is
the number 1 cause of trans failure. Excessive heat makes the rubber parts
brittle, alters the friction co-efficient of the fluid and it's lubricating
qualities.
If the manufacurer thought he could get away with delivering a vehicle
that took off in 2nd gear that's what they would have done. There are 3 or
4 speeds in a trans for a reason, to keep the engine in it's power band and
reduce stress on components. The friction surfaces of the clutches and
bands you are trying to protect will outlive the bearings and bushings in
the gear sets under normal operating temps and conditions. What you'll end
up with is some trans technician remarking on how good these parts look when
he throws them away while overhauling it because the seals and bushings are
all blown out.
If you want to extend the life of your trans, put it in drive, let it shift
itself. Make sure you keep the fluid cool and clean. If you get stuck,
don't rock it back and forth from dr to rev.
Steve G.
"sf/gf" <sf9...@kart.com> wrote in message
news:K_hgc.15061$k05....@newsread2.news.pas.earthlink.net...
DriveSpy
extended driving in very slow and go traffic (probably 15 minutes with slowest
speed 5-10 MPH) I have been leaving the trans in 2 or 3. This gives me better
control with the throttle, i.e. not having to go brake/throttle/brake/... for
much of my commute. I mean this thing upshifts to third so fast anyway under
light load that I figure I might as well leave it there.
Bill Funk
>>Everytime auto trannies shift, they wear. Whether the shift is up or
>>down, they wear.
>>Auto makers recommend that you leave a modern auto OD tranny in OD
>>unless the tranny starts to 'hunt', in which case you take it out of
>>OD.
>>
>>That said, on long downhills, downshifting can save wear on the
>>brakes, while helping you to maintain a safe speed. The single
>>downshift isn't causing much wear, and the engine braking saves wear
>>on the brakes. *In theory*, the other drivers will be able to
>>understand what's going on.
>>In traffic, though, another consideration comes into play; many
>>drivers really aren't paying much attention to what's going on around
>>them, and will actually miss the fact that the vehicle in front of
>>them is slowing down without those bright red lights to bring it to
>>their attention. In this situation, I use the brakes instead of
>>downshifting; it helps the other drivers keep from buying the back of
>>my vehicle. It also reduces the wear on the tranny.
>>
>>Without actually knowing what's going on in *your* tranny, it gets
>>hard to diagnose it. General rules tend to break down when we attempt
>>to apply them to individual units. (This is one reason why Jim's
>>replies can be rather long; he does a good job of trying to cover all
>>bases.)
>
>That's all true, but the original poster was asking about his alleged
>habit of manually downshifting it whenever he was coming to a red
>light, or a stop sign.
>
>Jeez!
>
Um, yes...
That's why I said, "In traffic, though, another consideration comes
into play; many drivers really aren't paying much attention to what's
going on around them, and will actually miss the fact that the vehicle
in front of them is slowing down without those bright red lights to
bring it to their attention. In this situation, I use the brakes
instead of downshifting; it helps the other drivers keep from buying
the back of my vehicle. It also reduces the wear on the tranny."
--
Jim Warman
as a grade retarder providing the road surface isn't going to cause
troubles. Depending on load and surface conditions, engine braking could
cause the rear wheels to slide rather than roll.
As far as using engine braking to reduce speed in normal driving.....
'forcing' components to apply will accelerate wear. Much wiser is lifing
early..... if there's a stop light or some other impediment to traffic flow,
better fuel mileage will be realize from lifting early, light brake
application and recover less speed than if we start from still.
All things being equal, we may not even notice any extra wear from the
forced downshift but there is so little to be gained (real or imagined) that
it doesn't make good sense. Though I have performed many manual forced
downshifts in my long and illustrious life ( nobody else going to blow my
horn), there has rarely been any requirement for it. When in doubt, read the
owners manual.....
"Tiger" <Mike...@cfl.rr.com> wrote in message
news:4WXec.423030$B81.6...@twister.tampabay.rr.com...
sachin
the
> freeway, and thereby use "engine braking" to aid in slowing down.
>
> Will the transmission be damaged if I regulary down-shift???
>
Probably not.
However, make sure to touch your brakes lightly to show other traffic
(behind you) that you are slowing down.
Also, avoid downshifting in slippery conditions......you can always control
brake pressure or just lift off the brakes if you start to slide.....but
when you downshift to slow down you give up a certain amount of control.