A success story: 5x drain/refill on '98 ls400 trans

[WhizkidTN]

I used to do all my cars/vans ATF changes by draining out the old, refilling and then using the cooler lines did a quickie start/stop of the engine to get more of the old out of the torque converter until it turned mostly new looking. I was in danger of cavitation of the ATF pump (a very bad thing) each time I did this. I have also always installed either an external trans cooler or the Magnefine trans in-line filter so getting access to the lines was not really that much of a problem.

I stopped doing this and have instead moved to the drain/fill method (which is the OEM method for my latest car anyway). I just did it twice after driving many miles on the 1st drain/fill. Now I have decent confidence that I have much cleaner/newer ATF without totally "shocking" the tranny with totally new fluid. ATF is pretty cheap anyway since I DIY'd it (using 12 quarts of Amsoil OE Synthetic ATF on my Optima).

FWIW: The total capacity of my tranny is 8.24 Quarts (US). You can only drain/fill ~6 quarts at a time (OEM service method).

I'm sure other vehicles will benefit from this and other methods discussed as well.

 

[Hall]

Originally Posted By: ccs368
For example, say you have a 10qt total capacity which includes sump, torque converter, cooler, lines, etc. etc. and I drain 5 qts and refill with 5qts.

The spreadsheet after 1st drain says 50% new and 50% old. This is easy to understand and not really debatable.

I agree with the spreadsheet in that scenario. I consider it fact, actually.

Originally Posted By: ccs368
However this is where the debate begins. Now I drive around and do the 2nd drain and refill the next day. The spreadsheet after 2nd drain now says 75% new and 25% old because the fudge factor is 1 where 5 qts new mixed together with the 5qts old/new still in the torque converter, cooler, lines, etc. from the 1st. Even though 10qts of new fluid was put in with a 10qt total capacity...it does not say 100% clean.


After that 1st drain, using your example, the math in the spreadsheet is right, but in the real-world, it's wishful thinking.

As I said earlier though, I've input our car's values and record ATF changes and I'm doing more frequent than normal fluid changes in order to get to 75% (or higher) and after that, I'll switch to changing the fluid every 15k, 20k, 25k miles or something....

 

[LeakySeals]

I've done a few Maxlife (with lubegard) full exchanges on the Escalade that calls for Dex VI. Its thinner than ACDelco Dex VI, but the transmission seems to like it. I also used it in Toyota transmissions running T-IV and WS. Not sure how good it would be for an older Dex III being so thin. I know my Dex III transfer case didn't like it. Shuddered turning corners.

 

[MaximaGuy]

Originally Posted By: 1JZ_E46
I think there is something to be said for leaving some old fluid in a high mileage tranny. Also, messing with cooler lines on a high mileage car (with lots of plastic) risks more expensive damage and repairs to the lines or heat exchanger/radiator.


As long as the D&F is slow and deliberate there shouldn't be a concern.
Now if a tranny is abused no amount of change will help - but if the ATF just got black even after 100K miles, then mechanically it is intact.
The is no plastic in the path of a transmission cooler lines - don't know where you have seen plastic in the path.

 

[1JZ_E46]

Originally Posted By: MaximaGuy
The is no plastic in the path of a transmission cooler lines - don't know where you have seen plastic in the path.


Not sure about Lexus/Toyota, but everything is plastic on BMWs. Pans, radiators, hose connections,

 

[MaximaGuy]

Originally Posted By: 1JZ_E46
Not sure about Lexus/Toyota, but everything is plastic on BMWs. Pans, radiators, hose connections,


Wonder why though and strange as well - there are 2 aluminium lines to the transmission and 2 copper lines from the radiator.
There is a hose that is clamped/crimped on both ends to make the connection from the radiator to the transmission.

 

[dlundblad]

Originally Posted By: Artem
Originally Posted By: dlundblad
Originally Posted By: Donald
Why didn't you exchange the ATF via the cooler line? You would have used 1/2 the ATF and done a better job.


Disconnecting some cooler lines are probably more hassle than they are worth. Crowded locations, hard to find clips/ connectors etc.

A little wasted ATF can be the lesser of 2 evils.


Yes but instead of mixing 30% new fluid with 70% old fluid and repeating 5x to finally get a decent % of new fluid in the system is a waste. Besides, the new fluid is instantly contaminated by the old fluid it comes in contact with. I prefer the cooler line DRAIN of all the old fluid until fresh new fluid starts coming out of the hose. This way you know that 99% of the old juice has been removed from the transmission.


No kidding?

 

[Boss302fan]

At least he did change out most of the fluid and had a good time doing it. Not everyone can get under the car and do a cooler line atf change... It also sounds like he had the fluid so what the heck. Good thing is, he did get some fresh fluid in that tranny. Great car and solid transmission.

 

[CincyDavid]

I'd do the same thing...no point in taking the chance of introducing breakage or new leaks.

I have had several cars that really felt nice after a transmission fluid change...the most obvious was a Ford ZX2 with the F4EAT Mazda automatic in it...felt like a new car for the first 5000 miles or so after a fluid change. Then it gradually started feeling and behaving like its old self.

 

[philipp10]

Originally Posted By: nthach
I've always been an advocate of the suck and fill/spill and fill for transmissions vs. a cooler line or machine flush. Even if it's messier it's gentler to a tranny.



"gentler to a tranny.".....that's preposterous. How can new clean fluid be "gentler"....

 

[DoubleWasp]

Highest mileage vehicle I did a complete cooler line exchange on had 322K miles. I've literally never had an issue from doing a complete exchange. But I also never do a complete exchange, or any type of trans fluid replacement without adding a filter.

Sonnax discovered that doing either drain-and-fill or cooler line exchange actually causes an increase in contaminants after the fact, as the new fluid clears out material that the old fluid could not.

The 322K vehicle was an NPR truck, which has a large spin-on trans filter from the factory. The filter was changed at the same time as the cooler line flush.

 

[SteveSRT8]

Lots of ridiculous misconceptions still alive here.

There is no such thing as a flush machine. Every single one I have seen is a passive set of containers with new fluid going out and old fluid coming in, perhaps a sight glass to monitor clarity.

I have owned them and stopped into literally dozens of shops to look at their equipment. Always the same.

So, if the machine does nothing to force fluid in or out, the car's trans pump does the work, there simply is nothing to harm anything.

Like DW above, we have performed this on very high mileage cars with great success and regularly on our vehicles as well.