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Posted: 4/19/2017 11:54:06 PM EDT
Premise:  A particular automatic transmission holds 12 quarts of ATF.  This particular model has a drain plug.  The drain pan holds 5 quarts of fluid. The other 7 quarts are in the torque converter or elsewhere in the transmission, and won't come out if you pull the plug.

So...

You drain it once.  Replace the 5 quarts of ATF.

So now you have 5 quarts of new fluid and 7 quarts of new.

You drive the vehicle a little and mix up the fluid.

Now you drain 5 more quarts.  And add five new fresh quarts.

And then drive it.  Drain out five more quarts of oil and add in five new quarts.

So...  the second and third drains took out some old, and some new oil.

After three drain and fills, how many quarts of old fluid, and how many quarts of new fluid are mixed up in the transmission?

Go--
Link Posted: 4/19/2017 11:57:31 PM EDT
Forcing new fluid through the system has got to be easier than guessing at the mix rate of old and new and slightly newish.
Link Posted: 4/19/2017 11:58:40 PM EDT
Let's see...carry the one...borrow...tire size divided by pi...


All of them!
Link Posted: 4/19/2017 11:59:39 PM EDT
You use a pump and pull the trans lines off of the cooler, you should be able to extract and replace all of it easily, without pulling the plug a million times to get "new" fluid in.
Link Posted: 4/20/2017 12:01:27 AM EDT
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Quoted:
You use a pump and pull the trans lines off of the cooler, you should be able to extract and replace all of it easily, without pulling the plug a million times to get "new" fluid in.
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But OP's approach is like saying "If I have a glass full of ice, and I fill it with bourbon, then I drain all the fluid from it, then fill it with bourbon, then drain all the fluid from it, then fill it with bourbon, then drain all the fluid from it, why did I park my car in my neighbors pool?"
Link Posted: 4/20/2017 12:03:04 AM EDT
you got enough new stuff in there 

ETA I did something similar but with power steering fluid recently and I kept doing it until it looked better
Link Posted: 4/20/2017 12:04:09 AM EDT
The only time I've ever taken my truck back to the dealer is to have them replace all 16 quarts of ATF in my transmission.  I work my truck hard, drive it hard, and tow a lot.  

A few hundred bucks every few years is cheap insurance.
Link Posted: 4/20/2017 12:05:48 AM EDT
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Quoted:
But OP's approach is like saying "If I have a glass full of ice, and I fill it with bourbon, then I drain all the fluid from it, then fill it with bourbon, then drain all the fluid from it, then fill it with bourbon, then drain all the fluid from it, why did I park my car in my neighbors pool?"
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Quoted:
Quoted:
You use a pump and pull the trans lines off of the cooler, you should be able to extract and replace all of it easily, without pulling the plug a million times to get "new" fluid in.
But OP's approach is like saying "If I have a glass full of ice, and I fill it with bourbon, then I drain all the fluid from it, then fill it with bourbon, then drain all the fluid from it, then fill it with bourbon, then drain all the fluid from it, why did I park my car in my neighbors pool?"
Link Posted: 4/20/2017 12:07:15 AM EDT
Is the car on a treadmill. 
Link Posted: 4/20/2017 12:07:46 AM EDT
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Is the car on a treadmill. 
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No, it's in a pool. We've covered this already.
Link Posted: 4/20/2017 12:09:40 AM EDT
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Quoted:
No, it's in a pool. We've covered this already.
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Quoted:
Quoted:
Is the car on a treadmill. 
No, it's in a pool. We've covered this already.
Maybe not, I mean nobody seems to have taken the phase of the moon into account here.

*eta*
Pretty sure there's a hypotenuse in there somewhere too.
Link Posted: 4/20/2017 12:10:44 AM EDT
You are leaving in about 41% of the total fluid each time. 
That leaves 5 qts of old the first time
About 2 the second
.8 something the 3rd...

I think... 
Link Posted: 4/20/2017 12:10:57 AM EDT
Its a math question.

The answer is not...  just disconnect the trans-cooler return line and pump out all the old fluid.
Link Posted: 4/20/2017 12:16:05 AM EDT
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Quoted:
Its a math question.

The answer is not...  just disconnect the trans-cooler return line and pump out all the old fluid.
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Each change leaves 41% old fluid.  0.41^3=8% old fluid after three changes
Link Posted: 4/20/2017 12:16:13 AM EDT
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Quoted:
You are leaving in about 41% of the total fluid each time. 
That leaves 5 qts of old the first time
About 2 the second
.8 something the 3rd...

I think... 
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nope you change 41% and 59% of the old stays
Link Posted: 4/20/2017 12:16:18 AM EDT
Ok fine, 87% of the fluid was new now it is 100% contaminated
Link Posted: 4/20/2017 12:18:53 AM EDT
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Quoted:


Each change leaves 41% old fluid.  0.41^3=8% old fluid after three changes
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59% stays each time or about 20% after 3 "flushes"
Link Posted: 4/20/2017 12:21:47 AM EDT
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Quoted:
59% stays each time or about 20% after 3 "flushes"
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Quoted:
59% stays each time or about 20% after 3 "flushes"
Yup.  I had it backwards because OP can't type, and I obviously have reading comprehension issues.

Quoted:
Premise:  A particular automatic transmission holds 12 quarts of ATF.  This particular model has a drain plug.  The drain pan holds 5 quarts of fluid. The other 7 quarts are in the torque converter or elsewhere in the transmission, and won't come out if you pull the plug.

So...

You drain it once.  Replace the 5 quarts of ATF.

So now you have 5 quarts of new fluid and 7 quarts of new.

You drive the vehicle a little and mix up the fluid.

Now you drain 5 more quarts.  And add five new fresh quarts.

And then drive it.  Drain out five more quarts of oil and add in five new quarts.

So...  the second and third drains took out some old, and some new oil.

After three drain and fills, how many quarts of old fluid, and how many quarts of new fluid are mixed up in the transmission?

Go--
Link Posted: 4/20/2017 12:25:59 AM EDT
I cut out a bunch of little paper squares, numbered to represent the different fill and drain cycles. I acted it out by taking 5 from the original 7 and arranged them in a homogeneous sequence. Did this for each of your cycles. Got a quart or less than the original fluid remaining each time.

Does this help? IDK

Yes I'm really bored
Link Posted: 4/20/2017 12:26:33 AM EDT
the problem is after another 5 quarts you get down to 12% and if you do it again 7% so it takes a lot of fluid to flush out all the old stuff BTW this assumes you get a 100 mix ratio and I have no clue if that actually happens. I would drive it for a few days between changes
Link Posted: 4/20/2017 12:27:23 AM EDT
Whoa!

None of this decimal bullshit.  I want to see this done with fractions!
Link Posted: 4/20/2017 12:29:53 AM EDT
Have you tried dowsing the tranny?
Link Posted: 4/20/2017 12:32:48 AM EDT
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Quoted:
59% stays each time or about 20% after 3 "flushes"
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That's what I got.
Link Posted: 4/20/2017 12:33:27 AM EDT
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Quoted:
Whoa!

None of this decimal bullshit.  I want to see this done with fractions!
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1/5 of 12 quarts.

ETA: 343/728 quarts.
Link Posted: 4/20/2017 12:34:49 AM EDT
(7/12)^3 is the percentage of old oil after 3 changes. Right around 20%
12*0.20 is 2.4 quarts of old oil.
Link Posted: 4/20/2017 12:35:11 AM EDT
87.
Link Posted: 4/20/2017 12:35:51 AM EDT
No one is actually answering the question. Sure, (0.58333)^3=0.198 so about 20% is the old oil, but that doesn't answer the question. The answer is about 2.4 quarts of old oil and about 9.6 of new oil.

ETA
So another interesting bit is you have removed about 15-9.6=5.4 quarts of perfectly good oil. It is kind of wasteful.
Link Posted: 4/20/2017 12:36:54 AM EDT
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Quoted:
Whoa!

None of this decimal bullshit.  I want to see this done with fractions!
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so the first time you change you leave behind 59% of the old fluid

step 2 you leave 34% 
step 3  20.%
step 4  12 %
step 5  7%
step 6  4%
step 6  2.4%
step 7  1.4%
 
No fractions only % 
Link Posted: 4/20/2017 12:37:31 AM EDT
Quoted:
Premise:  A particular automatic transmission holds 12 quarts of ATF.  This particular model has a drain plug.  The drain pan holds 5 quarts of fluid. The other 7 quarts are in the torque converter or elsewhere in the transmission, and won't come out if you pull the plug.
So...
You drain it once.  Replace the 5 quarts of ATF.
So now you have 5 quarts of new fluid and 7 quarts of new.
You drive the vehicle a little and mix up the fluid.
Now you drain 5 more quarts.  And add five new fresh quarts.
And then drive it.  Drain out five more quarts of oil and add in five new quarts.
So...  the second and third drains took out some old, and some new oil.
After three drain and fills, how many quarts of old fluid, and how many quarts of new fluid are mixed up in the transmission?
Go--
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The first drain removes 41.7% old ATF and leaves 58.3% old ATF.
Then you fill it, run the motor to mix it evenly.
The second drain removes 5 quarts of a mix of old and new ATF. x/5 = 58.3/100. if you remove 5 quarts, 2.91 quarts is old ATF. and  2.09 is new ATF.
Then you fill it, run the motor to mix it evenly. You have 34.08% old ATF.
The third drain removes 5 quarts of a mix of old and new ATF. x/5 = 34.08/100. If you remove 5 quarts again, 1.7 quarts is old ATF and 3.3 quarts is new ATF.

You have 15 quarts of new ATF mixed in, it's a trick question because some of the new gets drained out, or 5.39 quarts gets drained out.
So, 9.61 quarts is new ATF. 2.39 quarts is old ATF.
Link Posted: 4/20/2017 1:01:23 AM EDT
79% of your fluid is new, 21% is old.
Link Posted: 4/20/2017 9:19:55 AM EDT
Link Posted: 4/20/2017 9:26:51 AM EDT
87! Wot did I win?
Link Posted: 4/20/2017 9:58:22 AM EDT
Long story short it would cost less just to have it flushed fully and not retain any portion of the old ATF
Link Posted: 4/21/2017 12:02:15 AM EDT
I think I did the math right in my response. That's like 99 in arfcom ASVAB.
Link Posted: 4/21/2017 12:13:21 AM EDT
2.4 quarts of old ATF left, assuming a fairly complete mix between each change
Link Posted: 4/21/2017 12:20:34 AM EDT
The answer is 87 quarts of stupid. You are wasting transmission fluid and being impractical.
Link Posted: 4/21/2017 12:24:10 AM EDT
I went to art school
Link Posted: 4/21/2017 12:24:47 AM EDT
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Quoted:
Have you tried dowsing the tranny?
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My witchin' sticks kept pointing to his dick. 
Link Posted: 4/21/2017 12:27:59 AM EDT
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Quoted:
My witchin' sticks kept pointing to his dick. 
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Quoted:
Have you tried dowsing the tranny?
My witchin' sticks kept pointing to his dick. 
Then it was working
Link Posted: 4/21/2017 12:40:37 AM EDT
Link Posted: 4/21/2017 12:50:42 AM EDT
Quoted:
2.4 quarts of old ATF left, assuming a fairly complete mix between each change
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I agree, I got 2.4 qt of old fluid left.
Link Posted: 4/21/2017 12:55:35 AM EDT
cheaper to just replace the transmission
Link Posted: 4/21/2017 12:57:04 AM EDT
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Quoted:
Whoa!

None of this decimal bullshit.  I want to see this done with fractions!
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The ARFcom method is to never change the fluid, blow it up, & get new fluid with the new transmission...
Link Posted: 4/21/2017 4:27:32 AM EDT
Don't forget to replace the filter too.
Link Posted: 4/21/2017 4:32:53 AM EDT
The answer, obviously, is 87 quarts.
Link Posted: 4/21/2017 4:41:35 AM EDT
5:7
58% old remains (7/12).
Change 1: 7 parts old.
Change 2: 7*.58 = 4.06, 4.06 parts old remain.
Change 3: 4.06*.58 = 2.35, 2.35 parts old remain.

80% new fluid, GTG.
Link Posted: 4/21/2017 4:57:55 AM EDT
Buy a new car.
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