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will shifting "D" to "N" to halt spoil the gearbox


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#1
KiLLisHik

Posted 03 June 2005 - 09:25 AM

KiLLisHik

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ive this liking of shifting from "D" to "N" when slowing down to a halt.

when nearing the red light, i wld shift to N at a reasonable distant to
stop (not needing to accelerate anymore),and apply brake until it
gradually stop.

most of the time, slowing down to a red light, traffic jam, or even going
downslope at high speed, i wld shift to "N" until i need to push again, i
shift back to "D".

im not sure if this method is right/wrong. but i have the naive tot tht i
cld save some fc wit this regular shifting. not too often tho cus tell
myself tht it will wear and tear the gearbox faster than normal

i hope to know the fact abt tis, not feeling or assumption.

#2
eddievh

Posted 03 June 2005 - 11:04 PM

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If you love your transmission so much,don't do such thing so often.
The 2nd one(N while Coasting) is very tortures to transmission. When you
put N while coasting at high speed then you engage back D the transmission
will mabuk kejab don't know which gear(planetary gearset,valve body and
solenoid all mabuk) normally Gb will select 3rd gear then very fast shift
to top gear(4Th) this will unnessary wear 3rd and 4th gear friction lining.
Automatic are mean to be automatic which traslate no manual gatal tangan
shift the gear lever.

#3
5uckmi

Posted 04 June 2005 - 07:31 AM

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No matter what your speed are.......
As long as your engine are running.
As long as you are not shifting to P,R or any low gear (high engine
braking risks)
You are safe to shift N to D ot D to N.
Don't listen to those ppls who know nut in here to misleadind you.

#4
Dar

Posted 05 June 2005 - 03:20 PM

Dar

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Shock


#5
skyline77

Posted 12 June 2005 - 03:25 PM

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Changing D to N and vice versa could cause severe gearbox problem. Of
course, the prob would not be instantenous but it will affect the gearbox
life. Do u want to save some petrol by changing D to N and get your
gearbox ruin? Gearbox is very expensive.. so think twice before doing that.

The best practice is, leave the AT gear at D, and only change it to N and
P when:
--- a long stop (e.g. long waiting time at traffic light or waiting for
your gf to finish shopping)
--- parking

if u r in traffic jam (stop and go) or brief traffic light stop, keep it
at D (will save wear and tear).

#6
soulover

Posted 13 June 2005 - 11:02 AM

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I don't know who is the one that misleading.

Shifting from D-N-D when cruising is very dangerous!
-Your car might stall when cruising on N, causing losing braking power
(brake pump booster not working).

You won't save fuel at Neutral. It will spoil your gear box instead. Same
goes with revving engine at Neutral.

Agree with skyline77 to some extend. Unless u gonna stop for abot 10 mins
or so, better not change to N. The longest traffic lightIf stop before is
only 3 minutes. For 15 mins stop, better off your engine for heat will
build up at the catalytic converter and causes damages.

#7
J2EE

Posted 13 June 2005 - 08:29 PM

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I assume those of you who post here with arguments of for and against
shifting to N or let the gear stay in D, pls share the reasons why it will
spoil the gearbox or otherwise. If you can, pls be specific why -
mechanically. Appreciate the lessons.

#8
skyline77

Posted 14 June 2005 - 02:17 AM

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Changing from D to N while driving could cause 'shock' to the torque
convertor and the whole gearbox component. This 'shock' would cause
premature wear and tear, especially to the valve in the gearbox.

Another reason, when you are going downhill in D, without accelerating
(foot is off the accelerator pedal), petrol is already at it minimal and
thus no point in changing it to N (furthermore, you are eliminating engine
braking effect which is a better practice than using service brake when
going downhill).

For fuzzy logic equipped gearbox (those in Proton Perdana), the gearbox
will automatically drop one gear if it sense the car is going downhill and
helps you decent properly with a better traction.

For car without fuzzy logic gearbox, try changing to 3 and not to N.
Losing engine braking (as said by soulover) could cause accident due to
lose of traction.

#9
soulover

Posted 14 June 2005 - 09:22 AM

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As said by skyline77, the "shock" or rather the engagement of torque
converter is in fact one of the most deadly enemy to the lifespan of a
gearbox, as far as tear and wear is concerned.

The above topic is already discussed several times by the forummers and i
concluded not to change D-N-D after i read Daddy Fixit(a mechanical
engineer with PhD in automotive engineering) article about this topic
published in theStar Sunday magazine.

For some automatic transmission car especially those older generation or
Proton cars, I can undetstand that the whole car rattling like crazy if
not shift to D. But for the sake of the very expensive gearbox, i urge u
stick to D.

I also understand those uncle or grandfather who used to drive manual
will sure ask u to change to N coz it's a good practise for manual driven
car. But sad to say, they are wrong!

Some say that if Keep to D when car is stopping will build up heat in
gearbox thus spoiling the gearbox. I can tell you again they are wrong.
Quoted Daddy Fixit, the heat actually build up when the car is travelling
where power losses when transmitting the engine generated torques to the
wheels not when the car is idling. The auto gearbox nowadays have a
hydraulic cooling system that will automatically cool down the gearbox
when the car is not moving. It's a total different mechanism compare to
manual gearbox.

Some say holdind brake when geared at D will stress the engine and the
brakes. I can tell you, it won't. At D, the potential energy holded by
the brake is nothing stressful comparing when u press your throttle from
idling state. U can imagine the total weigth of the car(say 1200kg/11760
Newton) is suddenly loading the engine when u press your throttle from
idling state. So, the stress on the engine when holding at D is
incomparable to what your engine can take. Stressing your brake? How much
is your brake pad? RM40? How much is your gearbox then? RM20,000? No need
to elaborate further.

All in all, stick to D when idling and please let the "automatic" gearbox
fulfill its destiny as a "automatic" gearbox. No itchy itchy hands like
wat Skyline77 said before.



#10
kcfu

Posted 14 June 2005 - 09:54 AM

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no biggie here lar... as long as u dun drop to reverse when the car is
still moving towards the front and vice versa. oh ya... change yur ATF
on time.Wink