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.

Hope this helps,
Michael

 

When the TL will require to have the fluid replaced, I will take it to one of my customers who as a T-Tech Transmission Service machine and be done with it.

I find Honda's method of ATF fluid servicing ridiculous (Over $80 CDN at the dealer) for 3 quart of ATFZ1 fluid with labour.

It was the same way with my previous Honda Odyssey, I never let the dealer service the transmission fluid nor did they ever do an oil change. I prefer to do business with people who are trained to do this type of service and do it all day instead of letting the dealer hand it over to their newest employee on training do it and strip the threads on the oil pan.

Best regards

frenchnew

 

Or, you can just click on this link for a spreadsheet that does the same thing.

 

Impressive work by both of you

 

Hey Michael Wan, I notice you frequent BITOG, are you the same person?

Anyhow, good to see you here too. But from what I think if you were to spend the same amount of ATF it is the best to do more frequent change with drain and refill than changing it multiple times in the same day. Because your worn out ATF will be change constantly and not staying in your tranny for as long of a time. If you change it multiple times during the day, you have a higher percentage of fluid that got changed but the wear and tear afterward stay in your ATF for the entire 30k duration.

It is like brushing your teeth and flossing every evening vs not brushing or flossing for 3 month and then visit the dentist for deep cleaning. Both maybe at the end of 3 month, but the amount of wear and tear on your teeth will for sure be less on brushing and flossing every day.

 

Pandabear,
It's the same Michael Wan on BITOG.

Michael

 

BITOG is REALLY addictive. See you back over there!