Questions about transmission fluid

wrote:
> Bob Jones wrote:
>>>> 2- Is transmission flush recommended?
>>> NEVER. Drain and fill 3 times, with some driving between each cycle...
>>>
>> Do you really need to do it 3 times? The service manual doesn't say.
>
> The owner's manual says to do it once, and that's what the service
> schedule is intended to accomplish.
>
> The "drain and fill 3 times routine" is mentioned, but this is
> specifically to get rid of contamination caused by using non-Honda
> fluid. At that point, you do have to get the majority of the fluid
> out.
>
> That's what the Honda shop manager told me when I asked about this.
> They only drain and refill once for a tranny fluid change, in other
> words.
>
> That's probably enough in most situations. There are plenty of people
> doing more, and I'm marginally one of them. Let the appearance and
> smell of the tranny fluid be something of a guide.
>
> My Accord V6 has 28,000 miles and the fluid looks and smells almost
> like new. That means one fluid change is all it's getting until it
> gets considerably more miles.
>
> My MDX has 28,000 miles also, and the fluid smelled somewhat nasty and
> was turning brown. The first time I changed it at this mileage, the
> appearance really didn't change, it still looked bad. The second
> change (6 miles later), it looked pretty good. Now I'll wait until
> the end of the summer heat and change it again. And, then probably put
> it on a 15,000 mile routine for a single drain and fill as long as we
> have it.
>
> Remember, you get a higher percentage of contaminants out at higher
> mileage because they've built up more (so each change makes more of an
> impact, percentage-wise). It makes some sense to change it fairly
> often after 45,000 or 60,000 miles. But not much sense to change it
> very often before then. You're only trying to dilute the contaminants
> to a reasonable level. That is, you're diluting the contaminants to
> what the transmission would have at, say, 30,000 miles. Each change
> after that brings the total contaminants back in line with that 30,000
> mile baseline.
>
> Or you can change fluid like crazy and perhaps achieve a 15-20,000 mile
> baseline. But the dilution method will never get you even 80% much
> less 90% "new" fluid, and the tranny doesn't need that anyway. The
> math is an interesting study in futile maintenance. Each successive
> change gets about 40% of the remaining contaminants out, so the law of
> diminishing returns sets in pretty fast.
>
but as you started out by saying, the "3 times" routine is essential if
the wrong fluid was used.

I have a 1999 Accord EX V6. At about 95 Kms I had the tranny replaced
due to slipping. Once they put in the new tranny I switched too Castrol
Synthetic ATF. Once I switched I noticed the shifts were smoother and
generally the car ran better, seemed to have more power, maybe just me.
I know have 210Kms on the car and the tranny still shifts smooth and
has been serviced regularly by the local garage who is a Honda
specialist. I would be interested if anyone else has gobe this route
and what are your results.

On the flush question, the local garage drains and fills, he says that
flushing is not a good idea.


jim beam wrote:
> wrote:
> > Bob Jones wrote:
> >>>> 2- Is transmission flush recommended?
> >>> NEVER. Drain and fill 3 times, with some driving between each cycle...
> >>>
> >> Do you really need to do it 3 times? The service manual doesn't say.
> >
> > The owner's manual says to do it once, and that's what the service
> > schedule is intended to accomplish.
> >
> > The "drain and fill 3 times routine" is mentioned, but this is
> > specifically to get rid of contamination caused by using non-Honda
> > fluid. At that point, you do have to get the majority of the fluid
> > out.
> >
> > That's what the Honda shop manager told me when I asked about this.
> > They only drain and refill once for a tranny fluid change, in other
> > words.
> >
> > That's probably enough in most situations. There are plenty of people
> > doing more, and I'm marginally one of them. Let the appearance and
> > smell of the tranny fluid be something of a guide.
> >
> > My Accord V6 has 28,000 miles and the fluid looks and smells almost
> > like new. That means one fluid change is all it's getting until it
> > gets considerably more miles.
> >
> > My MDX has 28,000 miles also, and the fluid smelled somewhat nasty and
> > was turning brown. The first time I changed it at this mileage, the
> > appearance really didn't change, it still looked bad. The second
> > change (6 miles later), it looked pretty good. Now I'll wait until
> > the end of the summer heat and change it again. And, then probably put
> > it on a 15,000 mile routine for a single drain and fill as long as we
> > have it.
> >
> > Remember, you get a higher percentage of contaminants out at higher
> > mileage because they've built up more (so each change makes more of an
> > impact, percentage-wise). It makes some sense to change it fairly
> > often after 45,000 or 60,000 miles. But not much sense to change it
> > very often before then. You're only trying to dilute the contaminants
> > to a reasonable level. That is, you're diluting the contaminants to
> > what the transmission would have at, say, 30,000 miles. Each change
> > after that brings the total contaminants back in line with that 30,000
> > mile baseline.
> >
> > Or you can change fluid like crazy and perhaps achieve a 15-20,000 mile
> > baseline. But the dilution method will never get you even 80% much
> > less 90% "new" fluid, and the tranny doesn't need that anyway. The
> > math is an interesting study in futile maintenance. Each successive
> > change gets about 40% of the remaining contaminants out, so the law of
> > diminishing returns sets in pretty fast.
> >
> but as you started out by saying, the "3 times" routine is essential if
> the wrong fluid was used.

wrote:
> I have a 1999 Accord EX V6. At about 95 Kms I had the tranny replaced
> due to slipping. Once they put in the new tranny I switched too Castrol
> Synthetic ATF. Once I switched I noticed the shifts were smoother and
> generally the car ran better, seemed to have more power, maybe just me.
> I know have 210Kms on the car and the tranny still shifts smooth and
> has been serviced regularly by the local garage who is a Honda
> specialist. I would be interested if anyone else has gobe this route
> and what are your results.

i wrote castrol a while back and asked them if any of their atf's met
honda specs. they said "no", and that i should stick to honda atf. and
for my older civics, i can tell you from experience that it's always
caused severely harsh shifting - that's why i wrote. with non-honda
fluid in my 89 civic, you think the transmission is going to rip itself
free of the mountings at full power. returning to honda atf returned to
smooth shifting.

that said, about 98 or 99, honda got more sophisticated in their control
module programming - they retarded the ignition timing during the shift
so the power drops way back allowing smoother meshing of the new ratio.
[now, it's even more sophisticated with fly-by-wire - they throttle
back, not just retard ignition.] you seem to be benefiting from that,
but personally, i'd still use honda atf regardless.

>
> On the flush question, the local garage drains and fills, he says that
> flushing is not a good idea.
>
>
> jim beam wrote:
>> wrote:
>>> Bob Jones wrote:
>>>>>> 2- Is transmission flush recommended?
>>>>> NEVER. Drain and fill 3 times, with some driving between each cycle...
>>>>>
>>>> Do you really need to do it 3 times? The service manual doesn't say.
>>> The owner's manual says to do it once, and that's what the service
>>> schedule is intended to accomplish.
>>>
>>> The "drain and fill 3 times routine" is mentioned, but this is
>>> specifically to get rid of contamination caused by using non-Honda
>>> fluid. At that point, you do have to get the majority of the fluid
>>> out.
>>>
>>> That's what the Honda shop manager told me when I asked about this.
>>> They only drain and refill once for a tranny fluid change, in other
>>> words.
>>>
>>> That's probably enough in most situations. There are plenty of people
>>> doing more, and I'm marginally one of them. Let the appearance and
>>> smell of the tranny fluid be something of a guide.
>>>
>>> My Accord V6 has 28,000 miles and the fluid looks and smells almost
>>> like new. That means one fluid change is all it's getting until it
>>> gets considerably more miles.
>>>
>>> My MDX has 28,000 miles also, and the fluid smelled somewhat nasty and
>>> was turning brown. The first time I changed it at this mileage, the
>>> appearance really didn't change, it still looked bad. The second
>>> change (6 miles later), it looked pretty good. Now I'll wait until
>>> the end of the summer heat and change it again. And, then probably put
>>> it on a 15,000 mile routine for a single drain and fill as long as we
>>> have it.
>>>
>>> Remember, you get a higher percentage of contaminants out at higher
>>> mileage because they've built up more (so each change makes more of an
>>> impact, percentage-wise). It makes some sense to change it fairly
>>> often after 45,000 or 60,000 miles. But not much sense to change it
>>> very often before then. You're only trying to dilute the contaminants
>>> to a reasonable level. That is, you're diluting the contaminants to
>>> what the transmission would have at, say, 30,000 miles. Each change
>>> after that brings the total contaminants back in line with that 30,000
>>> mile baseline.
>>>
>>> Or you can change fluid like crazy and perhaps achieve a 15-20,000 mile
>>> baseline. But the dilution method will never get you even 80% much
>>> less 90% "new" fluid, and the tranny doesn't need that anyway. The
>>> math is an interesting study in futile maintenance. Each successive
>>> change gets about 40% of the remaining contaminants out, so the law of
>>> diminishing returns sets in pretty fast.
>>>
>> but as you started out by saying, the "3 times" routine is essential if
>> the wrong fluid was used.
>