Just did a 3x3 transmission fluid drain and thought I'd check the math.

I drained 3.5 quarts each time and refilled that much. This is under the assumption that whatever you drain is the same percentage of old/new fluid in the tranny (33% new fluid, 66% old fluid, 33% new will come out and 66% of old will come out if thoroughly mixed). That's my understanding, maybe someone with a chemistry background can tell me different.

On to the chart I made, it seems only 77% fluid is removed after the 3rd drain as you are basically taking out new fluid with old every time. Only a 4th or 5th will get close to 90% and even then you'll be draining mostly new fluid anyways.




Google doc for anyone who wants to check my math
https://docs.google.com/spreadsheets...it?usp=sharing

 

I locked the formulas but you can edit the quart amount for transmission and how much you refill/fill to see what percentages you get

I read the service manual and auto 3.2 trannys hold 7.4 quarts? Either case it would be 86% if that is correct.

 

You're just trying to introduce new fluid. A 3x3 isn't even required from the manufacturer from what I have read.

Some people do it over the course of three oil changes. We drive low enough mileage, that I'm probably going to just have mine changed once a year for the next three years.

there are a bunch of topics on this like:
https://acurazine.com/forums/third-g...dually-903027/

 

how about 7 times?