Transmission Fluid Change Theory

[Maverick Country Club]

Another case in point of over thinking things. I can prove that in 30 seconds with a dog and 2 doggie treats.

Prove it.

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[Ianrmcdonald84]

If you're doing what it's rated to, not exceeding it'll be fine. If you're consistently going hard or 60,80,90%. Definitely change fluid often. Way cheaper than trans work. Hundred of fluid, 2k trans? Drain and fill is pretty easy. To change a filter on that, you have to split the case, tear way more than you want to do in your garage. So basically never gonna happen.

Personally when I built transmissions, I built them "tight" close to the specs as I can, so after learning it it, (computer stuff) , customer will get the most life out of it before it goes out of spec and mechatronic assembly can't adjust anymore, then slipping, then failure. Everyone got new clutches, steels, bearings btw. If I'm opening it, I'm making sure it's never coming back.

 

[dalola]

The Maverick AT D&F is easy enough to do, and doing it more frequently is fine, if that's your thing. You just have to weigh the time/cost/waste factor against the benefit.

I follow a tweaked severe schedule, did the first D&F at 15K, again at 30K, then every 30K thereafter. I'm at 60K now, three D&F's (same for the PTU/RDU). I tow a couple times a year, some light off-roading, and typically don't push my Mav too hard. Expecting to get 200K lifetime from this truck. Everyone has to find their "comfort zone"...

 

[Maverick2022XL]

Prove it.

Easy I give the dog one, it knows I have the other and it won't leave me alone till I give it the second treat.

 

[Ianrmcdonald84]

Dalola is right. Find your comfort zone. Personally, mine is towing means heat, heat is enemy. Change it more often. My 24 doesn't have the tow package. Means 2k instead of 4k capacity i believe and an extra cooler. But I don't have anything to pull. If you do something stupid and over heat fluid, change it now.

 

[Mavster Mechanic]

My calculations are pushing me to strongly considering draining the 4 to 4.5 quarts that is easily removed from the drain plug and replacing the exact amount of fluid when changing the oil every other 5k change instead of 3 to 4 simultaneous flushes at one time at 30k. The same amount of fluid either way.

Legend: Miles on Fluid
Half 1X/10k Method
0k=0k
10k=(50%10k+50%0k)=5k
20k=(50%15k+50%0k)=7.5k
30k=(50%17.5k+50%0k)=8.75k
40k=(50%18.75k+50%0k)=9.325k
50k=(50%19.325k+50%0k)=9.6625k
60k=(50%19.6625k+50%0k)=9.83125k
70k=(50%19.83125k+50%0k)=9.91562k
80k=(50%19.91562k+50%0k)=9.95781k
90k=(50%19.95781k+50%0k)=9.97891k
100k=(50%19.97891+50%0k)=9.98945k
110k=(50%19.98945k+50%0k)=9.99473k
120k=(50%19.99473k+50%0k)=9.99736k
130k=(50%19.99736k+50%0k)=9.99868k
140k=(50%19.99868+50%0k)=9.99934k
150k=(50%19.99934k+50%0k)=9.99967k
160k=(50%19.99967k+50%0k)=9.99984k
170k=(50%19.99984k+50%0k)=9.99992k
180k=(50%19.99992k+50%0k)=9.99996k
190k=(50%19.99996k+50%0k)=9.99998k
200k=(50%19.99998k+50%0k)=9.99999k

Legend: Miles on Fluid
Half 3X/30k Method
0k=0k
10k=10k
20k=20k
30k=(50%30k+50%0k=15k; 50%15k+50%0k=7.5k; 50%7.5k+50%0k)=3.75k
40k=13.75k
50k=23.75k
60k=(50%33.75k+50%0k=16.875k; 16.875k+50%0k=8.4375k; 50%8.4375k+50%0k)=4.21875k
70k=14.21875k
80k=24.21875k
90k=(50%34.21875k+50%0k=17.1094k; 17.1094k+50%0k=8.55469k; 50%8.55469k+50%0k)=4.27734k
100k=14.27734k
110k=24.27734k
120k=(50%34.27734k+50%0k=17.1387k; 17.1387k+50%0k=8.56934k; 50%8.56934k+50%0k)=4.28467k
130k=14.28467k
140k=24.28467k
150k=(50%34.28467k+50%0k=17.1423k; 17.1423k+50%0k=8.57117k; 50%8.57117k+50%0k)=4.28558k
160k=14.28558k
170k=24.28558k
180k=(50%34.28558k+50%0k=17.1428k; 17.1428k+50%0k=8.5714k; 50%8.5714k+50%0k)=4.2857k
190k=14.2857k
200k=24.2857k

I am thinking that a consistent 10k old fluid is better than 4k to 14k to 24k old fluid.

No.

You can't average age of oil.
Adding some new oil does not make the old oil younger.

At 50k 6% of your oil will have 50,000 miles on it.

At 50k 12% of your oil will have 40,000 miles on it.

At 50k 25% of your oil will have 30,000 miles on it.

See where I'm going with this?

 

[sajohnson]

My calculations are pushing me to strongly considering draining the 4 to 4.5 quarts that is easily removed from the drain plug and replacing the exact amount of fluid when changing the oil every other 5k change instead of 3 to 4 simultaneous flushes at one time at 30k. The same amount of fluid either way.

Legend: Miles on Fluid
Half 1X/10k Method
0k=0k
10k=(50%10k+50%0k)=5k
20k=(50%15k+50%0k)=7.5k
30k=(50%17.5k+50%0k)=8.75k
40k=(50%18.75k+50%0k)=9.325k
50k=(50%19.325k+50%0k)=9.6625k
60k=(50%19.6625k+50%0k)=9.83125k
70k=(50%19.83125k+50%0k)=9.91562k
80k=(50%19.91562k+50%0k)=9.95781k
90k=(50%19.95781k+50%0k)=9.97891k
100k=(50%19.97891+50%0k)=9.98945k
110k=(50%19.98945k+50%0k)=9.99473k
120k=(50%19.99473k+50%0k)=9.99736k
130k=(50%19.99736k+50%0k)=9.99868k
140k=(50%19.99868+50%0k)=9.99934k
150k=(50%19.99934k+50%0k)=9.99967k
160k=(50%19.99967k+50%0k)=9.99984k
170k=(50%19.99984k+50%0k)=9.99992k
180k=(50%19.99992k+50%0k)=9.99996k
190k=(50%19.99996k+50%0k)=9.99998k
200k=(50%19.99998k+50%0k)=9.99999k

Legend: Miles on Fluid
Half 3X/30k Method
0k=0k
10k=10k
20k=20k
30k=(50%30k+50%0k=15k; 50%15k+50%0k=7.5k; 50%7.5k+50%0k)=3.75k
40k=13.75k
50k=23.75k
60k=(50%33.75k+50%0k=16.875k; 16.875k+50%0k=8.4375k; 50%8.4375k+50%0k)=4.21875k
70k=14.21875k
80k=24.21875k
90k=(50%34.21875k+50%0k=17.1094k; 17.1094k+50%0k=8.55469k; 50%8.55469k+50%0k)=4.27734k
100k=14.27734k
110k=24.27734k
120k=(50%34.27734k+50%0k=17.1387k; 17.1387k+50%0k=8.56934k; 50%8.56934k+50%0k)=4.28467k
130k=14.28467k
140k=24.28467k
150k=(50%34.28467k+50%0k=17.1423k; 17.1423k+50%0k=8.57117k; 50%8.57117k+50%0k)=4.28558k
160k=14.28558k
170k=24.28558k
180k=(50%34.28558k+50%0k=17.1428k; 17.1428k+50%0k=8.5714k; 50%8.5714k+50%0k)=4.2857k
190k=14.2857k
200k=24.2857k

I am thinking that a consistent 10k old fluid is better than 4k to 14k to 24k old fluid.

Great post! I appreciate you taking the time to do the calculations. Even though we drive our Badlands very little -- it'll be 4 years old in March and has ~8,000 miles on it -- we'll be at 10K miles next year.

We have an RV on a Sprinter cab-chassis. After doing a complete ATF change (incl. torque converter) which was a huge PITA, I came to a similar conclusion -- just drain and replace the 50%+ than is in the pan, but do it more often.

FWIW, it is common for shops to do it that way -- just drop the pan (if changing the filter) or pull the plug.

Many torque converters do not have a drain plug anyway. The jury seems to be out on power flushing transmissions, but of course that's always an option.

I plan to use your Half 1X/10k Method.

 

[Maverick Country Club]

No.
You can't average age of oil.
Adding some new oil does not make the old oil younger.
At 50k 6% of your oil will have 50,000 miles on it.
At 50k 12% of your oil will have 40,000 miles on it.
At 50k 25% of your oil will have 30,000 miles on it.
See where I'm going with this?

Hi David,
I’m trying to understand… You’re saying that your car has 50k, and the fluid is a mixture of:
6% of the original fluid, that was fresh at 0mi.
12% of the fluid has 40k on it because at 10k you drained 12% of the fluid and replaced it with fresh 0mi fluid.
25% of the fluid has 30k on it because at 20k you drained 25% of the fluid and replaced it with fresh 0mi fluid.
Is that it?

I will clarify what each part of my 50k calculation represents…

50k=(50%19.325k+50%0k)=9.6625k
The odometer reading is 50k when I remove the drain plug and only half of the fluid will drain. The other half will not drain as it is trapped in the torque converter.

(50%19.325k+50%0k)=9.6625k
This 50% represents the amount of used oil remaining in the transmission that will not drain as it is trapped in the torque converter.)

50k=(50%19.325k+50%0k)=9.6625k
The 19.325k represents the average mileage of wear on the fluid that won’t drain, which is a calculation of pervious changes every 10k.

(50%19.325k+50%0k)=9.6625k
This 50% represents the new fluid that I will use to replace what was drained.

(50%19.325k+50%0k)=9.6625k
This 0k indicates the new fluid has 0 miles of use.

(50%19.325k+50%0k)=9.6625k
This 9.6625k represents the average mileage of wear of the fluid mixture of 50% fluid with 19.325k of use and 50% of new fluid with 0 miles use.

I hope this better explains what I am doing, so it is easier to interpret the equation. Thank you for your interest, and if I can explain this better, the finding when understood are interesting to me and possibly reveal this method to be a better choice than the videos that tell us to drain, fill then drain again then fill, then drain again and fill at 30k. This theory is irrelevant if you flush the transmission, but I am not comfortable with that as I had to rebuild a transmission after getting a scheduled 50k flush years ago. I don’t trust the flush process or the people doing it.

Kind regards,
Larry

 

[Maverick2022XL]

Easy I give the dog one, it knows I have the other and it won't leave me alone till I give it the second treat.

To expand this is just a different way to state Peano's axioms. The doggie treat is the natural number, I am the successor function and the dog is treat counter. The fundamental rule of addition. Give me a treat feed the dog, the addition is how many treats did I feed the dog not how I feed the dog. All your grade school math is based on this and the rules that logically fall out of this.

Unless the dog dies or it finds food elsewhere it will keep coming back for another treat one at a time for potentially an infinite amount of times. That is how you prove all those rules aka induction.

Math is a logic based exercise not a language like taught in grade school. That is just one way of applying it, it is not the it. That they don't show kids this in grade school these days to my knowledge at least once before graduating should be criminal

 

[Mavster Mechanic]

Hi David,
I’m trying to understand… You’re saying that your car has 50k, and the fluid is a mixture of:
6% of the original fluid, that was fresh at 0mi.
12% of the fluid has 40k on it because at 10k you drained 12% of the fluid and replaced it with fresh 0mi fluid.
25% of the fluid has 30k on it because at 20k you drained 25% of the fluid and replaced it with fresh 0mi fluid.
Is that it?


Kind regards,
Larry

No. I'm not saying that at all. I'm saying that is what will happen if you follow through with your experiment.

Your theory is flawed.

 

[Joe Strummer]

Why do you go to only 5 decimal places, which equals 1 cm? I need it to the mm...

 

[Maverick Country Club]

Honestly, 30k. Drain and fill. But keep in mind its not going to be bright red like old school mercon v.

You would use 1/3 of the amount of fluid as the 3x30k or 1x10k methods.
According to my calculations, that would look like this…

Legend: Average Miles on Fluid Mixture
Half 1X/30k Method
0k=0k
10k=10k
20k=20k
30k=(50%30k+50%0k)=15k
40k=25k
50k=35k
60k=(50%45k+50%0k)=22.5k
70k=32.5k
80k=42.5k
90k=(50%52.5k+50%0k)=26.25k
100k=36.25k
110k=46.25k
120k=(50%56.25k+50%0k)=28.125k
130k=38.125k
140k=48.125k
150k=(50%58.125k+50%0k)=29.0625k
160k=39.0625k
170k=49.0625k
180k=(50%59.0625k+50%0k)=29.5312k
190k=39.5312k
200k=49.5312k

Kind regards,
Larry

 

[Maverick Country Club]

Why do you go to only 5 decimal places, which equals 1 cm? I need it to the mm...

Joe Strummer, you’re a rascal and you always will be!

 

[Maverick Country Club]

No. I'm not saying that at all. I'm saying that is what will happen if you follow through with your experiment.
Your theory is flawed.

David,
It’s possible it is flawed, but I would like details so I can understand how.
If you mix 50% red paint with 50% white paint, you will get a certain shade of pink. If you remove half of that pink paint and mix it with the same amount of white, the result will be a lighter shade of pink, and on and on. The difference is shades of pink vs miles of wear. This is relevant because you can’t drain all of the transmission fluid, it can only be removed 100% if you flush it or split the transmission.
I really think this theory is legit.
Thank you for your interest,
Larry

 

[Mavster Mechanic]

Partial drains and partial refills will dilute dirt & contaminates.

Partial drains and partial refills will add in some new additives.

But the old half stays old and only gets older.

The question that has not been answered is: what happens to
The old; older; eventually really old fraction that remains the second and third.... times you do this?

Weird example: if oil changes to vinegar; would you want to dilute it by half or take it all out (or as much as possible)?

Since you like thought experiments lets go a step further.

What if oil changes to vinegar (acetic acid) at 30k but does little harm. But if left in there until 40k further decomposes into hydrochloric acid and does great harm.

Would you want to leave any fraction of the old in there each time?

Not saying this is how it works.
Just a thought experiment for you.

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