Help needed with the math

[demarpaint]

I'm planning a transmission pan drop and filter change on my 93 Aerostar. It calls for 4 qts for a pan drop and 9.8 qts for a complete refill.

The math question, if I drop the pan and refill with lets say 5 qts, and want to do a fluid evacuation with a Miti-Vac, or drop a transmission line to get the fluid out, how many qts would I need to completely change the fluid in the system? Lets assume 5 qts was added to do the pan drop.

I remember reading somewhere how to calculate it, I can't find it and don't know how to estimate how much fluid would be needed. Is it as simple as about 5 more qts? Or is there some calculation they use?

As always thanks!


BTW no drain plug on the TC.

 

[morris]

useing math is overkill. just add small amounts till it gets full as its running. note: i have done this to only chryslers, dont know how other brands are checked.

 

[demarpaint]

Thanks for the reply, I realize that. My question is after the pan drop and the transmission is full I want to do a line flush in an attempt to exchange all the fluid that wasn't changed out to new ATF. So if the pan drop netted 5 qts total and the unit holds a little under 10 qts how much would you flush out to complete the job?

Another way of putting it is how much fluid would a transmission shop use in their machine to do a fluid exchange in a transmission holding close to 10 qts of ATF? Lets assume they didn't do a pan drop.

 

[charbaby]

Well, I have heard of others here at BITOG mention that they do 3 drian/refills over a short period of time...Ooooh, let's say a two week period. This should cover a high % of the fluid being replaced. In your case, 12 qts of ATF.
But, to answer your question the way you had asked, I'm sorry to say that I can't help you there, I wish I could! I'm sure others will chime in with the answer that your looking for.

 

[The_Jeff]

4/9.8= 40.8% new or 59.2% old.

Now put .592 to whatever power is your number of changes.

so .592^2 is 35% old fluid.
^3 is 20% old.
^7 is 2.5% old.

You're never going to get it all out. However if you can squeeze just a little more out each time it's a big positive, say by draining the TC by letting it sit overnight.

Another .9 quarts so it's exactly half an exchange each time would have 0.78% old after 7 changes.

 

[demarpaint]

Thanks, math and I were never good friends, LOL. So would drawing out another 7 qts, pumping out the pan twice for the sake of argument be about as close to draining all the old fluid out as I could get? Or since I can get ~4 qts out of the pan via extraction if done twice with along the 5 fresh qts from the pan drop be about all she wrote? There is no plug on the TC, and I realize getting it all out is impossible, I just want to get close.

Thanks again!