Safe to flush trans?

[Trav]

Originally Posted By: y_p_w
What does it really achieve other than a warm fuzzy feeling about getting out as much original fluid as possible? You'd think there's a reason why pretty much every modern automatic transmission will only drain less than 50% of the fluid through taking off a drain bolt and/or dropping the pan. The important thing to do is replenish the additives. That's also the case for a lot of fluids. I took care of a problem with my wife's Civic's power steering whine by simply adding less than 2 oz of OEM PSF. I did a full purge later, but that was more because it made me feel good and probably meant it would stay trouble free longer. However, what's the difference between 40% and 90%?

If it was so important that as much fluid be drained as possible, manufacturer's would have made that possible with a simple drain bolt at the torque converter.


So does that mean we can just change 2 qts of oil in a 5qt sump and get the same result?

 

[y_p_w]

Originally Posted By: Trav
Originally Posted By: y_p_w
What does it really achieve other than a warm fuzzy feeling about getting out as much original fluid as possible? You'd think there's a reason why pretty much every modern automatic transmission will only drain less than 50% of the fluid through taking off a drain bolt and/or dropping the pan. The important thing to do is replenish the additives. That's also the case for a lot of fluids. I took care of a problem with my wife's Civic's power steering whine by simply adding less than 2 oz of OEM PSF. I did a full purge later, but that was more because it made me feel good and probably meant it would stay trouble free longer. However, what's the difference between 40% and 90%?

If it was so important that as much fluid be drained as possible, manufacturer's would have made that possible with a simple drain bolt at the torque converter.


So does that mean we can just change 2 qts of oil in a 5qt sump and get the same result?

My wife's Civic has a 4.4 quart total capacity and the factory spec'ed change without a new filter is 3.2 quarts. They feel it's appropriate and there are thousands of Hondas approaching 200K miles with such oil changes.

And it's pretty well known in professional circles that wear tends to go up right after an oil change because the antiwear additives need to heat activate.

 

[DBMaster]

ATF lubricates and cleans, but beyond that performs very different functions from motor oil. Trying to equate changing oil with changing ATF is the stuff of high profit for establishments that sell transmission "flushes."

Here's an individual statement again. I have never done one and never will.

 

[Trav]

Originally Posted By: y_p_w
My wife's Civic has a 4.4 quart total capacity and the factory spec'ed change without a new filter is 3.2 quarts

All engines never take total fill from when they were built. Try changing 1.5qts next time.

This is just silliness, you either change the fluid or you don't. Adding a few ounces here and there or changing a few qts at at time is nonsense.
If it works for you go ahead on its your vehicle.

 

[y_p_w]

Originally Posted By: Trav
Originally Posted By: y_p_w
My wife's Civic has a 4.4 quart total capacity and the factory spec'ed change without a new filter is 3.2 quarts

All engines never take total fill from when they were built. Try changing 1.5qts next time.

This is just silliness, you either change the fluid or you don't. Adding a few ounces here and there or changing a few qts at at time is nonsense.
If it works for you go ahead on its your vehicle.

However, a lot of people think they're providing the maximum level of protection by getting out as much previous fluid as possible because it's "contaminated". These systems are designed to accept old fluid has assorted stuff suspended in the oil as well as filter out anything that is detrimental. Millions (perhaps even billions) of dollars of research has gone into making motor oils and transmission fluids that neutralize soot/acids/etc such that you don't have to worry about it remaining in the oil. Not to mention that it's been in there in that state for as much as 10K miles or more with OCMs or even longer with transmission fluids.

We have people complaining about no-filter oil changes not because they feel the filter performance is severely compromised, but because they didn't get out that additional 0.2 quarts of oil (or less) that was in the filter. When a transmission only removes 40-45% of the fluid that's in the reservoir via a simple drain and/or pan drop, we've got people thinking it's worthwhile to hook up some machine that will make it about 90-95%.

 

[Jim Allen]

Originally Posted By: y_p_w
These systems are designed to accept old fluid has assorted stuff suspended in the oil as well as filter out anything that is detrimental


Inaccurate statement. There has long been arguments between engineers and bean counters over AT filtration. Up to the point where electronic solenoids were used, your statement was somewhat accurate and the bean counters won the argument over whether or not to add better filtration. Those old transmissions could deal with a lot more contamination than the newer ones can. When electronically controlled transmissions appeared, there was a LOT more trouble with transmission failures due to contamination and eventually, those failures forced the bean counters to let loose of a few pennies.

You may have read my Eleftherakis and Kalil comment above. They did decades of research and came up with a lot of data that finally changed the industry's mind over filtration and oil cleanliness. The result... improvements in the way transmissions are manufactured (cleaner assembly) and the oil filtered (enhanced filtration in some cases).

Basically, there is an oil cleanliness level below which the wear and operation of the trans is satisfactory or optimal, and above which where it is not, or is sub optimalor even detrimental. It varies somewhat from trans to trans but a contamination level of 25 mg/l or less is satisfactory and 10mg/l is optimal. Some years back, Ford thought an ISO cleanliness code (2-digit) of 18/15 was optimal. A used trans of the past with 70K might be at 25/18 if it never had a change. A one number change in that code is approximately a 50% increase or decrease in the particle count range

I refer you to several SAE papers, 2001-01-0867 "Automatic Transmission Hydraulic Cleanliness" (Nieuwland & Droste), 99PC-418 "Optimizing Automatic Transmission Filtration" (Eleftherakis & Khalil), 900561 "Development of a Lab Test Contaminant for Transmissions" (Eleftherakis & Khalil). Those papers, and others based on testing that started in the '80s, sold me on the premise that there ain't no such thing as trans oil that's too clean. And for about $20 bucks, you can have that with a Magnefine or similar inline filter, or a more expensive spin on.

Besides external filtration, I'm more or less on board with regular D&Fs AFTER the first complete change has been done. OR if you have done a particle count and found low contamination levels. If you are just shooting in the dark, and the car has never had a full fluid exchange or enough D&Fs that will replace most of the oil, the likelihood is that the oil is running in a suboptimal/detrimental state of cleanliness. How much that matters depends a lot on how long you intend to keep the vehicle.

 

[Jiblet]

Originally Posted By: Jim Allen
.... You can do repeat D&F but how many times must you do that to have a meaningful effect? A cooler line or passive flush is so easy on most cars and gets the job done with less waste...


Sir, I have read many of your posts and articles, particularly referencing the E&K findings and I am convinced that you are spot on in your assessments and recommendations. I wish I had discovered the information sooner.

I now know about the E&K findings of early wear and the advantage of an early fluid change along with supplementary filtration in addition to the sump filter. I have recently done a pan-drop to replace the filter and about 1/3 of the fluid. I also installed a magnafine inline filter. But I do have a question about how to proceed with maintenance.

I am trying to wrap my head around the differences between a passive/coolant line exchange versus serial drain and fills with time spent driving to allow for mixing.

Please correct anything I say that is inaccurate, auto transmissions are new to me.

My options are
1) do consecutive drain and fills of 1/3 the fluid allowing time between to drive/mix the fluids. Assuming perfect mixing, the serial dilution will require 7 or 8 iterations to remove upwards of 95% of the original fluid.(if my math is correct)
or
2) do a cooling line exchange, allowing the trans to pump out old fluid while drawing in fresh fluid. If it's the full volume exchanged, then 9 quarts out/ 9 quarts in, or there about.

I understand the inefficiency of the serial dilutions method but in my mind the transmission is being used throughout the range of gears allowing mixing within the entire transmission.

What I am trying to understand is whether or not the coolant line exchange method reaches all, or nearly all, the fluid in the transmission. My intuition says no, because the trans isn't actually working, it's just passively pumping (I assume through the path(s) of least resistance). Maybe I am way off base and the passive exchange actually does replace a high percentage of the original fluid. Please let me know if that is the case.

The vehicle in question is a 2008 Jeep Wrangler JK with 42RLE transmission. I installed a B&M aux cooler at about 5k miles. I don't tow with it or do any hard 4-wheeling. At 60k I did a pan drop filter and fluid change and added a magnafine inline filter on the return side of the aux cooler.

Thanks for your input!

 

[y_p_w]

Originally Posted By: Jiblet
What I am trying to understand is whether or not the coolant line exchange method reaches all, or nearly all, the fluid in the transmission. My intuition says no, because the trans isn't actually working, it's just passively pumping (I assume through the path(s) of least resistance). Maybe I am way off base and the passive exchange actually does replace a high percentage of the original fluid. Please let me know if that is the case.

The vehicle in question is a 2008 Jeep Wrangler JK with 42RLE transmission. I installed a B&M aux cooler at about 5k miles. I don't tow with it or do any hard 4-wheeling. At 60k I did a pan drop filter and fluid change and added a magnafine inline filter on the return side of the aux cooler.

Thanks for your input!

No machine can do that. One can only hope to achieve a high proportion. Also - there's bound to be some amount of new fluid introduced during the process that's flushed out before it's spent much time in the system. So there's still some "waste" inherent in the process.

I personally wouldn't spend $200 for someone to do this for me. I have a distaste for paying someone to do something I feel I can do myself even without all that fancy equipment. Maybe four drain and fills on my wife's Civic costs as much as sending it to a shop, but at least I'm doing it myself. I'm using the OEM spec fluid and not some substitute that some quickie lube place has on hand. Or I'm not paying the "rape me" prices at a dealer.

 

[Jim Allen]

Jiblet: Is that a small jib sail ( : < ). Couldn't resist... sorry.

Unless the fluid is showing some sign of deterioration, by adding the Magnefine and doing the pan drop and partial fluid change, you are OK in terms of fluid contamination and you don't need to do anything more for the moment, IMO. You change the oil for two reasons; to replace worn out fluid or to decrease contamination levels. The added filter and the partial change definitely took care of the contamination aspects and the new oil will have bolstered the old oil that remains. If the remaining oil was in decent shape, you could go another 20-50K this way IMO. The safe interval for the Magnefine is 30K, so you might consider a full cooler line fluid exchange at that time and at least a 60K interval after, if not 100K (with a Magnefine change at appropriate intervals). No need to drop the pan and change the pan filter again as the Magnefine will carry a lot of the contaminant load. A cooler line flush gets nearly 100 percent of the oil... perhaps a little less if you don't drop the pan and start the cooler line flush with a pan full of new fluid. If your pan has a drain plug, you are golden. You can simply drain the pan first, refill with new oil and then start the cooler line exchange. I agree with ypw.. with most vehicles a cooler line exchange is so ridiculously easy taht if you are the least bit handy, you can save mucho dinero. If you can drop the pan yourself and install the MF filter, you are more than capable of doing a cooler line exchange.

 

[Jiblet]

Originally Posted By: Jim Allen
Jiblet: Is that a small jib sail ( : < ). Couldn't resist... sorry.


Ha! you're not far off. I was the smallest in the sailboat, if I wasn't paying attention they'd shout "JIB" to wake me up to do my job. But in the jeeps I was the turkey who had to get out into the mud to engage the hubs. Jib sails and turkey giblets....

Thanks for the input. I have a MityVac so its easy to draw out the pan fluid.
I'll keep it all in mind for the next round of maintenance. Thanks again.

 

[HTSS_TR]

Originally Posted By: Jim Allen
I agree with ypw.. with most vehicles a cooler line exchange is so ridiculously easy that if you are the least bit handy, you can save mucho dinero. If you can drop the pan yourself and install the MF filter, you are more than capable of doing a cooler line exchange.

I was thinking about cooler line exchange when I do ATF for my cars, but knowing that I tend to screw thing up easily, so I did the easy/safe way with Mityvac, then refilled about 3-4 quarts each time. Did it 3-4 times was good enough for 8 quart sump.

Yes, I used 12-15 quarts instead of 8-10 quarts but it was idiot proof with Mityvac.