ATF Removed with each drain/refill

[The Critic]

I wrote this for the Acurazine, 3rd Gen TL section.

Thought I'd pass this along to my BITOG family as well.

For those of you who wonder how much old fluid remains in your 5AT after each drain and refill, I've set up a formula that will calculate that.

Now, calculating the amount of fluid remaining after a single drain and refill is simple...you simply divide the amount of fluid removed by the total amount of fluid remaining. In the case of the TL, you typically remove 3 quarts per drain and refill out of the total 7.4 quarts.

So, 3/7.4=0.405 (40.5%) Subtracting from 100, this will give me about 0.595, which is about 59.5% of old fluid remaining.

Now if you do multiple drain and refills to remove as much fluid as possible during a short period of time say, by draining and refilling then driving a short distance before repeating the process, determining the percentage of old fluid within this new and old fluid "mix" can be somewhat challenging.

I've found an accurate way of doing this, and that is to:

1) Divide the amount of fluid removed from the system with each drain and refill. In the case of the 3rd Gen TL, a single drain and refill removes 3 quarts out of the total 7.4 quarts in the system. A quick trip to the calculator tells me that a single drain and refill removes 40.5% of the 7.4 quarts.
2) Take 40.5% and subtract if from 100%, this will give you 59.5%; thus, 59.5% of fluid is left in the system.
3) Now take 59.5%, and put it into decimal form, which would be 0.595. If you are planning to do three drain and refills, input 0.595 into your calculator and raise it to the third power. I get a value of 21%, which means that after drain and refilling the transmission three times, and driving a short distance in between each refill, 21% of the fluid in the system is "old" fluid.

Now, if you have a "target" amount of fluid that you want to have remaining in the system, say you want to have 20% old fluid remaining in the system, the following this formula:
1) Divide the amount of fluid removed from the system with each drain and refill. In the case of the 3rd Gen TL, a single drain and refill removes 3 quarts out of the total 7.4 quarts in the system. A quick trip to the calculator tells me that a single drain and refill removes 40.5% of the 7.4 quarts.
2) Take 40.5% and subtract if from 100%, this will give you 59.5%; thus, 59.5% of fluid is left in the system.
3) Take 59.5%, and put it into decimal form, 0.595.
4) Take your "target" amount of old fluid remaining in the system, say 20%, and put it into decimal form, 0.2.
5) Take log 0.2, and press equal, which will equal -0.7.
6) Then, then take log 0.595, which will equal -0.23
7) Divide log 0.2 by log 0.595, which in this case is -0.7/-0.23=3.04. Which means that you'll have to do 3 drain and refills to remove 80% of the fluid.

Michael

 

[JHZR2]

reminds me of the calculations I had to derive for tanks and stuff in chem engineering 101

JMH

 

[Gary Allan]

Michael

Simplify ...simplify ..simplify

 

[TallPaul]

I have done these calculations for my automatic trannies. I wish I could do them for power steering but capacities of power steering systems are about impossible to obtain short of an actual total drain and refill. A good assumption seems to be about 1.5 qts though.

Another thought, for if the capacity is unknown. Do a blotter on a white file card of the fluid before each partial change. When the blotter looks about as good as new fluid, quit.

 

[eljefino]

That is nice and scientific, but why would I want to change something 3.73129 times?

Stop at the 0.595 to the power of x, and leave x a whole number, a whole number of changes, and do a couple quick calculations instead of messing with logs. ("Gee, what happens if I change it three times... four times?)

Whether one gets 19% or 21% of the fluid changed, they should call it "close enough" or do a whole flush again.

You are lucky, mathematically, that your car takes exactly 3 quarts in a change. Otherwise you'd be considering the remnants of the leftover bottles to see if it's economically feasible to buy another case of ATF.

I had to do something like this flushing water out of a 2.2 gallon cooling system when I had one new gallon of 50/50 antifreeze and one new gallon of full strength. Was only willing to drain radiator which held slightly less than a gallon. Hint: I used the 50/50 first.

 

[The Critic]

quote:

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Originally posted by Michael Wan:
3) Now take 59.5%, and put it into decimal form, which would be 0.595. If you are planning to do three drain and refills, input 0.595 into your calculator and raise it to the third power.
Michael

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I did say that. Look at what I quoted.

Michael

 

[kenw]

Geesh this really puts world hunger in proper perspective.....

I once had a spreadsheet that calculated the future cash value of my 401k, which was mostly company stock including self and company-match contributions, projected salary increases based on industry trends, inflation, fees and early withdrawal penaties and taxes....it was fabulous and many of my coworkers used it. We tweaked it for several years.


then the company went belly up.

 

[tdimaniac]

quote:

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Originally posted by kenw:


then the company went belly up.

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enron?

a while back, if you had bought $1000 worth of nortel stock and a $1000 worth of budweiser (the beer in cans and not the stock), then drank the beer over a year and cashed in the cans, the bud would have been the better investment.

 

[MolaKule]

On what basis what the third power factor derived?

 

[Drew99GT]

quote:

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Originally posted by MolaKule:
On what basis what the third power factor derived?

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For 3 total drain and fills. You raise it to the power of each drain and fill to find out what % of old fluid remains.
3 was used for illustration purposes