How many miles for transmission fluid to mix thoroughly?
 

I'm going to be changing the ATF on my CDI. I'm going to do 2 or three extract and fills. After the first extract and fill, how many miles would you guess it would take for the new fluid to completely mix with the old?

The mixing would be immediate, however I'd leave the new / old mix in the trans for say 10,000 miles or some multiple of oil changes that gets you close to 10,000. ( might as well be under he car once. ) 3X changes is excessive. At most I'd change now, drive 10 K then change once more at say 15 K additional mileage.

This allows the new fluid to pickup / dissolve worn friction material and hold it in suspension. ( The old oil would be saturated with material. )

I've taken apart a few trans in the 165 K mile range that had very little friction material laying around. Most of the friction material ends up caked to the inside of clutch drums and needs mechanical means to remove. A fluid change and a drive down the street does nothing in this case.

Also, the torque converter makes for a great centrifugal separator so a few mile change won't help here.

My reasoning for doing multiple changes via a fluid extractor is get the fluid as pure as possible without a lot of effort.

FWIW my calculations on the 722.6, assuming I can drain 3.5 quarts out of 7.9, are as follows:

1st drain: 44% new

2nd drain: 69% new

3rd drain: 83% new

Again, for minimal effort and expense, I wind up without relatively pure/new fluid and I don't have to get under the car....except when I need to replace the filter and clean the pan.

Isn`t there a drain plug on the Torque Converter?
Or are these newer MB`s so high tech now they eliminated the drain plug?

If you are using an oil sucker, you are only getting the fluid from the pan.

Seems like a lot of wasted ATF for what you are trying to achieve.

Charlie

No TC drain plug after 99 on 722.6. So, without the fancy machine that the dealer has, all anyone can get out is the fluid in the pan: 3.5 quarts. If one wants to get more than that, multiple drain and fills have to be done. I'm happy to "waste" some ATF to get cleaner fluid.

On my 190D, my protocol has always been to suction the pan and replace the fluid with every oil change. It's about 2 qts each time. Every great while, I will replace the filter. Works.

I've pulled the cooler line and flush the trans instead of draining a refilling. Very effective.

Here is a fella doing it on his CDI. Long video, but the important procedure is begins at about 20 minutes into the video.
https://www.youtube.com/watch?v=-7IhwezUrUA


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Yeah, I'm more and more moving toward more frequent fluid changes and less frequent filter changes. I just dread getting under the car and removing the pan.

It's not that I mind the work of dropping the pan, but the area is so filthy and hard to clean that more dirt must go in that comes out.

i believe the TC drain plug was missing for 2 or 3 years only - 2000-2003 - doesnt hurt to check for it.

You can also use the cooler line to dump out nearly all of the ATF in the unit. There should be a union near the engine to undo, slip a hose on it or just put it into a large bucket and start the engine, the ATF will be pumped out.

You run it till it quits flowing then shut it down Z?

I do it 3 qts a time on benz, - I do the run till it spurts on General Motors products. (They hold quite a lot)

This technique also gives me a chance to flush the ATF cooler with a spray cleaner and rig the hoses backwards to flush the cooler with fresh ATF (I usually see some debris/clutch mud from the cooler flushing)

That's interesting...I didn't know that. I'll have to check for it on the 06.

Assuming it's been kept up regularly, even a pan drain and refill with a new filter *should* be good enough. That's all I'm able to do in my CLK430 (aside from a full exchange monkeying with the cooler lines) as it has no torque converter drain, and apparently it was enough to make MBZ happy with 39k fluid/filter changes after they decided the "filled for life" stuff was utter nonsense.

If I did have a torque converter drain, as I do on the W124, I'd certainly do it, but I tend to do the fluid and filter every 25-30k ahead of the MB-recommended interval to keep things working fine. It tends to still look pretty clean each service, even only getting what's in the pan and installing a new Mann filter, but it did have its first service with 4134 ATF at about 35k, so that could have something to do with it as well.

If it had 100k+ by the time I first serviced it, then I'd probably look at doing what you are doing. That's actually how Honda themselves recommend servicing neglected (and ultra-delicate) autos in their cars, IIRC it returns about 86% new fluid in those.

You need one of these to keep it all clean and Purdy. :D
Works very well.

Hotsy 500 Series Hot Water Pressure Washers


Charlie