Transmission Question re: manual fluid exchange - how many times?

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Old 04 Feb 2005, 06:09 pm   #1 (permalink)
Funky McCool14
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Default Transmission Question re: manual fluid exchange - how many times?

If one has 8 quarts of original transmission fluid capacity, dumps out
2 quarts by draining the pan, then adds 2 fresh quarts of synthetic
ATF, how may dumps will it take to have mostly synthetic transmission
fluid?

Let's see... 8 quarts old fluid minus 2 quarts old fluid drained = 6
quarts in the transmission system. Add 2 quarts synthetic, we now
have 6 quarts old and 2 quarts synthetic. The current ratio is 4
quarts old ATF to 1 quart Synthetic, so the transmission has 16%
synthetic after the first dump. I did it again when I replaced the
filter, so another 2 quarts was drained and 2 more fresh quarts of
synthetic was added. The problem here is that the fluid was no longer
pure old fluid. It was 16% synthetic.

So now that I added 2 more quarts of synthetic, what's the ratio of
old to new now? 24%? (50% of the original 16%, or 8%) 16+8=24%

The question is: How many times do I need to dump out 2 quarts and add
2 new quarts of synthetic to get mostly synthetic?

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Old 04 Feb 2005, 07:27 pm   #2 (permalink)
m Ransley
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Default Re: Transmission Question re: manual fluid exchange - how manytimes?

Is the fluid clean now, does what you have done helped, I would not
worry or try to get it all, I just drain it out every oil change or 2.
If it still wont shift synthetic wont help.

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Old 04 Feb 2005, 09:32 pm   #3 (permalink)
hachiroku
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Default Re: Transmission Question re: manual fluid exchange - how many times?

On Fri, 04 Feb 2005 19:09:11 -0500, Funky McCool14 wrote:

> If one has 8 quarts of original transmission fluid capacity, dumps out
> 2 quarts by draining the pan, then adds 2 fresh quarts of synthetic
> ATF, how may dumps will it take to have mostly synthetic transmission
> fluid?
>
> Let's see... 8 quarts old fluid minus 2 quarts old fluid drained = 6
> quarts in the transmission system. Add 2 quarts synthetic, we now
> have 6 quarts old and 2 quarts synthetic. The current ratio is 4
> quarts old ATF to 1 quart Synthetic, so the transmission has 16%
> synthetic after the first dump. I did it again when I replaced the
> filter, so another 2 quarts was drained and 2 more fresh quarts of
> synthetic was added. The problem here is that the fluid was no longer
> pure old fluid. It was 16% synthetic.
>
> So now that I added 2 more quarts of synthetic, what's the ratio of
> old to new now? 24%? (50% of the original 16%, or 8%) 16+8=24%
>
> The question is: How many times do I need to dump out 2 quarts and add
> 2 new quarts of synthetic to get mostly synthetic?



Your theory is good, but in practice I'm afraid you missed the mark.

Every time you drain and fill, the fluids mix! So, while the initial
calculation is right, thereafter the mixing causes less non-synthetic to
be replaced.

Math is not my strong point, but it is going to take a while...
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Old 05 Feb 2005, 10:10 pm   #4 (permalink)
Ken Peterson
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Default Re: Transmission Question re: manual fluid exchange - how many times?

On Sat, 05 Feb 2005 03:32:31 GMT, hachiroku <levin@ae86.gts> wrote:

I found this in a oil forum by some named "pitzel" which might be
interesting. Not sure of the logic, but it does make sense. Here's a
shortcut link: http://tinyurl.com/6mcpk

=============

"Well, that is a somewhat 'slow' way to change the ATF, and ends up
wasting a lot of fluid.

For example, my 4T60 transaxle holds 12L of ATF. If I change 2L or 17%
of the fluid at a time:

First Change:

17% New/83% Old = 83% old

2nd change:

83%*83% = 69% old

3rd change:

69% * 83% = 57% old

4th change:

57% * 83% = 47% old

5th change:

47% * 83% = 39% old

6th change:

39% * 83% = 33% old

7th change:

33% * 83% = 27% old

8th change:

27% * 83% = 25% old

9th change:

25% * 83% = 19% old

10th change:

19% * 83% = 16% old

11th change:

16% * 83% = 13% old

12th change:

13% * 0.83% = 11% old

nth change:

0.83^n = % old

Doing a pan drop evacuates approx. 8 quarts on the same transaxle,
leaving 4 in the torque converter.

First change: 33% old fluid
2nd Change: 11% old fluid.
nth change: (1-66%)^n

As you can see, using 16L of fluid with 2 pan drops replaces 89% of
the fluid. To do it 2L at a time, would take 24L of fluid to achieve
the same concentration of 'new' fluid.

Ultimately, you have to decide whether it is worth wasting a bunch of
oil to accomplish a change. I hate to recommend wasting oil, but
actually doing it 2L at a time does make significant sense if you
don't care about doing a filter change or any of the other benefits a
pan drop would provide."



>On Fri, 04 Feb 2005 19:09:11 -0500, Funky McCool14 wrote:
>
>> If one has 8 quarts of original transmission fluid capacity, dumps out
>> 2 quarts by draining the pan, then adds 2 fresh quarts of synthetic
>> ATF, how may dumps will it take to have mostly synthetic transmission
>> fluid?
>>
>> Let's see... 8 quarts old fluid minus 2 quarts old fluid drained = 6
>> quarts in the transmission system. Add 2 quarts synthetic, we now
>> have 6 quarts old and 2 quarts synthetic. The current ratio is 4
>> quarts old ATF to 1 quart Synthetic, so the transmission has 16%
>> synthetic after the first dump. I did it again when I replaced the
>> filter, so another 2 quarts was drained and 2 more fresh quarts of
>> synthetic was added. The problem here is that the fluid was no longer
>> pure old fluid. It was 16% synthetic.
>>
>> So now that I added 2 more quarts of synthetic, what's the ratio of
>> old to new now? 24%? (50% of the original 16%, or 8%) 16+8=24%
>>
>> The question is: How many times do I need to dump out 2 quarts and add
>> 2 new quarts of synthetic to get mostly synthetic?

>
>
>Your theory is good, but in practice I'm afraid you missed the mark.
>
>Every time you drain and fill, the fluids mix! So, while the initial
>calculation is right, thereafter the mixing causes less non-synthetic to
>be replaced.
>
>Math is not my strong point, but it is going to take a while...


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Old 06 Feb 2005, 07:51 am   #5 (permalink)
Daniel
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Default Re: Transmission Question re: manual fluid exchange - how many times?

Just focus on how much synthetic has been added on a net basis.
If you drain hot, and leave overnight almost another quart will come
out.
Three or four times, you've replaced most of the fluid.
If your numbers are correct, and you're draining 2 quarts out of 8 that
would be one fourth.
Just focus on how much synthetic has been added, since that's what you
want to know.
First time, you add 2.
Next time, you add 2, but remove one fourth of the previous 2 - equals
two fourths or one half quart new synthetic lost. Total remaining, two
new, plus one and a half prior quarts equals three and a half.
Next time you add two. Plus you lose one fourth of the prior 3 /12,and
so on.
It's a process of diminishing returns, but after a few times, you've
got most of it.
On my 4 cylinder, the total capacity is 6.7 qts., and draining over
night can remove around 2.8 qts., so you'd be adding new fluid more
rapidly.

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Old 06 Feb 2005, 01:27 pm   #6 (permalink)
Ken Peterson
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Default Re: Transmission Question re: manual fluid exchange - how many times?

On 6 Feb 2005 05:51:33 -0800, "Daniel" <nospampls2002@yahoo.com>
wrote:

Thanks! I did a quazi-fluid exchange based on reading the forums over
at BOBISTHEOILGUY - http://theoildrop.server101.com/cgi/ultimatebb.cgi

(main page: http://bobistheoilguy.com/ - great reading on both sites)

Basically one disconnects the fluid output line running from the
tranny to the radiator cooler, connects a line to it so it flows into
a container, starts the car and lets it pump out about 2 quarts until
the feed slows and bubbles appear. Then reconnect the line, refill
with Synthetic ATF, drive around a little, repeat 2 more times. I've
read that's a good way of getting the fluid out of the converter.

The question is, where does the fluid come from which is being pumped
out of the tranny to the radiator cooler? Is it from the pan or from
some circuit off the converter?

Anyway, yesterday I fed it 8 quarts of Mobil1 synthetic ATF with one
pan drain and the rest using the procedure above.

I feel pretty good about getting it more or less mostly synthetic by
now.

I figure a pan drain of the tranny at every oil change ought to keep
things peachy.

>Just focus on how much synthetic has been added on a net basis.
>If you drain hot, and leave overnight almost another quart will come
>out.
>Three or four times, you've replaced most of the fluid.
>If your numbers are correct, and you're draining 2 quarts out of 8 that
>would be one fourth.
>Just focus on how much synthetic has been added, since that's what you
>want to know.
>First time, you add 2.
>Next time, you add 2, but remove one fourth of the previous 2 - equals
>two fourths or one half quart new synthetic lost. Total remaining, two
>new, plus one and a half prior quarts equals three and a half.
>Next time you add two. Plus you lose one fourth of the prior 3 /12,and
>so on.
>It's a process of diminishing returns, but after a few times, you've
>got most of it.
>On my 4 cylinder, the total capacity is 6.7 qts., and draining over
>night can remove around 2.8 qts., so you'd be adding new fluid more
>rapidly.


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Old 06 Feb 2005, 03:29 pm   #7 (permalink)
MisterSkippy
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Default Re: Transmission Question re: manual fluid exchange - how many times?

On Fri, 04 Feb 2005 19:09:11 -0500, Funky McCool14
<FunkyMcCool@aol.com> wrote:

>If one has 8 quarts of original transmission fluid capacity, dumps out
>2 quarts by draining the pan, then adds 2 fresh quarts of synthetic
>ATF, how may dumps will it take to have mostly synthetic transmission
>fluid?
>
>Let's see... 8 quarts old fluid minus 2 quarts old fluid drained = 6
>quarts in the transmission system. Add 2 quarts synthetic, we now
>have 6 quarts old and 2 quarts synthetic. The current ratio is 4
>quarts old ATF to 1 quart Synthetic, so the transmission has 16%
>synthetic after the first dump. I did it again when I replaced the
>filter, so another 2 quarts was drained and 2 more fresh quarts of
>synthetic was added. The problem here is that the fluid was no longer
>pure old fluid. It was 16% synthetic.
>
>So now that I added 2 more quarts of synthetic, what's the ratio of
>old to new now? 24%? (50% of the original 16%, or 8%) 16+8=24%
>
>The question is: How many times do I need to dump out 2 quarts and add
>2 new quarts of synthetic to get mostly synthetic?



You'll never actually get ALL of the old fluid out but to do so is not
necessary. It isn't AIDS. A little doesn't contaminate a lot. For many
years I've been using a Might Vac hand pump, in between pan drops and
filter changes, to pull out 3 or 4 quarts of fluid yearly, then
replacing with fresh. It keeps the fluid fresh enough so that I have
never had a problem with an automatic transmission in 41 years of car
ownership. It may be just me and just anecdotal, but that is my
experience.
YMMV, of course
FWIW
DFB




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constitutional rights it acts lawlessly and the citizen can take matters into
his own hands and proceed on the basis that such a law is no law at all."
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