SodaLuvr

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 TSX, you typically remove 3 quarts per drain and refill out of the total 6.9 quarts.

So, 3/6.9=0.435 (43.5%) Subtracting from 100, this will give me about 0.565, which is about 56.5% 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 TSX, a single drain and refill removes 3 quarts out of the total 6.9 quarts in the system. A quick trip to the calculator tells me that a single drain and refill removes 43.5% of the 6.9 quarts.
2) Take 43.5% and subtract if from 100%, this will give you 56.5%; thus, 56.5% of fluid is left in the system.
3) Now take 56.5%, and put it into decimal form, which would be 0.565. If you are planning to do three drain and refills, input 0.565 into your calculator and raise it to the third power. I get a value of 18%, which means that after drain and refilling the transmission three times, and driving a short distance in between each refill, 18% 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 18% 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 TSX, a single drain and refill removes 3 quarts out of the 6.9 quarts in the system. A quick trip to the calculator tells me that a single drain and refill removes 43.5% of the 7.4 quarts.
2) Take 43.5% and subtract if from 100%, this will give you 56.5%; thus, 56.5% of fluid is left in the system.
3) Take 56.5%, and put it into decimal form, 0.565.
4) Take your "target" amount of old fluid remaining in the system, say 18%, and put it into decimal form, 0.18.
5) Take log 0.18, and press equal, which will equal -0.74.
6) Then, then take log 0.565, which will equal -0.247
7) Divide log 0.18 by log 0.247, which in this case is -0.74/-0.247=3.003. Which means that you'll have to do 3 drain and refills to remove 82% of the fluid.

Hope this helps,
Michael

jmathew34

how about flushing the tranny out? is this something that we shouldn't do especially if it's the first time changing the tranny fluid?

minkl81

iTrader: (2)

Wow... What a mathematician.
I think it will be cheaper to just flush it first time.

Zasker1

Actualy its cheaper to just never change it, just sell your car before you hit 75k and your golden~

goddsmack

You can't really essentially flush a tranny system out, you'd blow your pump if you did. In any tranny fluid, all you are doing is using the vehicle's pump to exchange fluid out. Even machines utilize the system's pump and either press on a bladder (Wynn's Machine) to push new fluid in or it just empties into a containment and you refill yourself (Mac Tool machine). So yes as long as you watch yourself, you can do it yourself.

You need to find a tranny fluid line, since I don't have an automatic I couldn't tell you where to find one that might be easily accessible, but the best bet is the tranny cooler lines.

a] First do the normal pan spill & fill (drain and refill).

b] You'll need an assistant for the rest

1) Find a tranny line, doesn't matter where, but disconnect it and as quickly as a person can start the car, turn it off immediately while keeping your thumbs blocked off both ends. I mean this as quickly as possible, because otherwise remember your tranny has high pressures and it will squirt all over your engine bay, if you're not fast enough. Now of course, if you going the tranny cooler route, all you need to do is just figure the direction of flow.

2) Once you found direction of flow, attach a section of flexible piping from the effluent, into a bucket (I would mark on the outside of the bucket, quart levels).

3) Start the car, and the line should start to empty into the bucket. I don't know the total capacity of the TSX's auto tranny, but to be safe drain out no more than a 1 quart.

4) Stop the car, and add a quart through the dipstick

5) Repeat the process, until you do this about 4 times. The reason I mention 4 is I just completed my sister's '92 accord and it's approx a 6.5 quart system so with the 2.5 on the original spill & fill and 4 on the exchange portion, it's close enough. Plus I notice that after about the 2nd time, my fluid was coming out pink enough (I used clear PVC tubing to check out my fluid look).

6) After you disconnect everything, remember you'll still have a slight amount of fluid in the line that you connected as an extension, so check your fluid level. Honda auto trannies are generally measured with the engine off (as opposed to running, in most vehicles). I would run the engine till it reachs operating temperature and check the level then (again with the engine off).

Other notes:
-Honda's need a specific amount of friction modifiers in their auto trannies (so they can slip better), so either buy the Honda brand from the dealer or I believe Royal Purple makes a compatible ATF for Honda's.
-The reason for this is Honda's auto's are not your traditional planetary gear system tranny, rather they are based on a manual tranny system, but instead of utilizing syncro's, a wet clutch system is used in place and therefore the friction modifiers allow the clutchs to slip a bit more than usual (otherwise you get chattering and excessive heat if the modifers aren't used).
-Tranny filters in Honda's are generally not replaced unless a complete tear down of the transmission is accomplished as the filter is inside the tranny casing.