Transmission flush question

Post by **MadeInJapan** » 01 Nov 2006, 20:36

Good deal! I answered your PM...now let's see the write-up (as with MAC you can't post pics...you can send them to me). As a mod, I can just edit your post and add the pictures into it!

dasapir · Post by **dasapir** » 03 Nov 2006, 07:42

MIJ,
I still have a few questions remaining regarding the modified flush and then a possible suggestion or two which might slighty modifiy the new "modified " technique.

With respect to the ATF running through the radiator, is that impelled through or sucked out from the return line by a potential vacuum created by the revolving gears? My hunch is that it is propelled through because the system does not have a tight enough seal due to the dipstick orafice.

Second question is about how much ATF is in the radiator system at any one time? Again, my intuitive hunch would place it around 1 qt.

The reason I ask is, if in fact, the ATF is propelled/ pushed through the radiator then once the transmission-to-radiator line is disconnected the dirty ATF would remain in the radiator and would not be accessible during the flush.

So here is my proposal to slightly modify your "modified" technique. After draining the transmission pan and adding the new ATF one should turn on the engine and let the car idle for a minute or two. This would allow the 3 quarts of fresh new ATF to mix with the remaining old ATF (5 qts) in the system, thus diluting the old ATF by approximately 40% (3qts/8qts). So the old inaccessible ATF in the radiator would now be "less dirty" by about 40%. The 1 quart left would be 60% dirty or stated differently 0.6 of a dirty quart would remain in the radiator

Then the standard flush would be carried out in the recommended fashion and after reconnecting the inlet line to the radiator the ATF that remained in the radiator (40% cleaner) would now be washed back into the system. This would create a "cleaner" flush.

Previously (the original "modified" technique) there would still be a dirty: clean ration of 1:7 or about 12%. Now the ratio of dirty to clean would be 0.6:7.4 or about 8%. So, just by running the engine for a minute one would have improved the flush by 4%. In other words, wait a minute to do the disconnect before proceeding with the "standard" flush.

Whaddya think? Am I correct in this or did I err with my lack of understanding as to how the system works?

Post by **luketrash** » 03 Nov 2006, 10:52

There's a lot less in the radiator than you expect. the radiator sits higher than the tranny pan.. when the car is off, it pretty much empties out. The pump basically barfs fluid out the top pipe down the element in the radiator to warm up the tranny fluid (or regulate its temperature I guess)

I've replaced a couple of these radiators in my truck and my volvo 960 in the past two years and both had maybe 1/4th cup of fluid in them.

Post by **MadeInJapan** » 03 Nov 2006, 17:19

Good answer, luketrash...So, you have your answer.
No need to turn on the car and let the fluid circulate to dilute what you put in...you want it to flush behind, or push the bad stuff out that's in the system (at least this is how I see it).

dasapir · Post by **dasapir** » 04 Nov 2006, 08:23

To both Luketrash and MIJ thank you for your overall help, comments, and support.

Post by **MadeInJapan** » 04 Nov 2006, 09:50

dasapir wrote:To both Luketrash and MIJ thank you for your overall help, comments, and support.

I suppose that really an even better way to flush the system would be to figure out a way to add fluid through the radiator opening (like those flush machines work), but so far I really haven't seen a good way to do this.

I have added to the tranny flush write-up that on the newer (P2- or '01 on) Volvo's flow the opposite direction. In other words, when you take the tanny-to-radiator line off, you actually let the tranny flush out of the upper hose connection on the radiator and the way we flush with our cars from the hose still connected to the trannyhose itself. Volvo actually recommends you take the hose off at the tranny, plug the tranny hole with a plastic stopper, and drain from the hose still attached to the radiator.

Post by **luketrash** » 04 Nov 2006, 11:12

Well I bought a 12 quart case of the cheap stuff, but it'll be better than my burned fluid that's in there now.

Thanks a lot to MIJ for the photo writeup sticky post!

I've got my FCP parts in hand now, which included 5 crush washers.. The weather got warm again, so I'm going out to change out the trans fluid now. I need to go get a long funnel at the store I guess... I remembered to get the 1/2" tubing

Oddly enough, I once got a bunch of craftsman pliers at an estate sale, of goofy types and I never had figured out a use for these duckbilled backwards pliers, but they are exactly like the tool MIJ used to release pressure on the retaining ring at the radiator.

Post by **MadeInJapan** » 04 Nov 2006, 14:12

Thanks for the thanks, but all of the pictures are dasapir's, and 99% of the write-up is his too. I just looked it over, added a few things, corrected a few typo's and it's posted. Glad it helped you. Remember that you want some hose that has an INSIDE diameter of 1/2 inch, otherwise it will be too small.

Post by **luketrash** » 04 Nov 2006, 16:55

It all went well and only took me an hour from start to finish.

I used 12 quarts of fluid in total and it was finally coming out of the tubing red towards the end.

I'm 99% sure that this is the original transmission fluid which is 12 years old. 108k miles on it! Burned and on its way to being black, not brown. The transmission works fine though, so that's good. It shifts the same as it did before the change now too. All is well.

The jug on the right is the first gallon. The one one the left is the second gallon. The measuring jug in the middle was the last gallon's worth.. Finally turned red!

This measuring method worked great too, because I ended up with the transmission having just the right amount of fluid, using up all 12 quarts.

Post by **MadeInJapan** » 04 Nov 2006, 17:28

I'm glad that folks are using the pinned "modified" method and having successful flushes. I'm going to need to do this too real soon. I flushed mine at just under 100K and I'm just over 130K now. I understand that once you begin flushing it's best to keep a schedule of about 30K miles, but I'm sure using synthetic can prolong that interval a few more miles...maybe 35 or 40K?