DIY transmission flush questions

[mvmcali]

i was thinking about trying to flush the 'whole transmission system' as per video i saw. my understanding is if you just drain the pan and refill, you do NOT replace all the fluid that is hanging out in the torque converter , radiator/cooler , etc

my Q: does the return hose (from the radiator/cooler back to the torque converter) has suction on it created by the upstream pump? i understand there is a pump in torque converters which push the fluid thru the various components and then into the pan . there it is then pushed thru the output hose to the radiator/cooler to close the loop.

BUT... if i disconnect the output hose at the radiator and then dump it into a bucket to catch old fluid and i attach another hose to the radiator input nib into a clean bucket of new fluid... and i then run engine... will a vacuum be created to pull the new fluid into the system as the old fluid is pumped into bucket?

i want to know if this works before i destroy my automatic transmission

[macgiver]

The cooler "RETURN" in a RE4R01A , for EXAMPLE only ( my J30 trans) supplies "Rear Lubrication" - according to my ATSG auto trans manual . There is "Front Lubrication" NOT involving the cooler at all , being supplied off pressure utilized at or near the Lockup fluid ckt. Front & REAR Lubrication would be " moving parts , bearings , bushings etc. " transferring energy . Other half of fluid ckts are "control" w/ accumulators , valves, solenoids, pistons,chk valves etc. etc. which direct and actuate the different "functions" and engage things. I can only assume REAR Lubrication is less critical to a car at stand still , for your lubing the output components mostly.
But FRONT Lubrication would include input shaft , input gears?, torque converter whatever and to INTERRUPT this by diconnecting the cooler may starve something , and badly if done for a considerable length of time (like more than 60 seconds ?? )
Now it would be good to disconnect the cooler , reverse blow out into WHITE rag to inspect amount and type of debris , if any. Then while cooler is "drying out from the Brakleen or whatever was used , you may connect both loose hoses together with a 5/16? union. While refilling the pan and running the fluid out w/engine idling for 15 -20 seconds- then refill .
To "flush" more thoroughly the Converter, possibly with a big funnell and someone adding fluid while another person is under car and partially blocking the open drain hole of the pan to sort of "be in step "and have a continuous flow , In 'n Out , would probly clear out a converter in like 60 + seconds.

Of course with the disconnected cooler hose , IF fluid is coming off from the converter, would be a more thorough operation , quicker I imagine here , but how would you know how long is too long to starve the 'FRONT Lube" components ??

Also there is a "spec" for the flow of fluid going out to cooler , AND you measure before cooler the volume
"dumped" into a vessel over time vs how much less passes when going through the cooler into same pan - same time interval . Like 15 seconds 2 pints must be "passed" just the hose into pan ,and then when passing through cooler into pan you must see a minimal drop ,in the same time interval , like 1 3/4 pints now -NO LESS , for EXAMPLE . Good time to check that spec when cleaning/disconnecting cooler , or especially when adding an aftermarket cooler - some may restrict too much ( many times the bigger ones with LENGTHY tubes) so you have better cooling, BUT choking off critical lubrication!

You gotta get or see an automatic transmission manual for YOUR vehicle , they contain everything you need to know,test, maintain - whatever - your specific transmission.

[Mike W.]

...my understanding is if you just drain the pan and refill, you do NOT replace all the fluid that is hanging out in the torque converter , radiator/cooler , etc

Correct. But a flush is regarded by many, including myself, as a bad idea. Just do a drain and fill 3 times, with a little bit of driving in between of course, and you will likely exchange over 90% of the fluid. With less time and trouble than trying to do a flush.

Or just do a drain and fill in conjunction with oil changes the next 3 times. You've already got the drain pan under there, just slide it over a bit and pull that plug too.

[macgiver]

Mike W. is absolutely correct in that if you simply do the "pan drop" drain/fills often enough , like3-4 years & 35 kmi , and some prefer to "bunch-up" a series of 2 or 3 like he said,say when your out w/over 135 kmi or something ; 3 changes in a matter of months or even weeks.

That kind of TLC and virtually NOBODY will need to do those remedial / more extreme measures I laid out two posts back . Though checking the flow rate & or pressure drop in "fitting" aftermarket cooler install is always smart thing to attempt , peace of mind ya know.

[BubbaFL]

I've done this twice. Piece of cake - pop the lines off the cooler, run the engine, let the fluid pump out while you're pouring fresh fluid in via the dipstick hole.

Try to keep adding at about the same rate fluid is coming out. I marked a five gallon bucket at one-gallon increments to have an idea of what was coming out.

When the fluid coming out is the color of new fluid, you're done.

While you're under the truck consider adding an inline filter. I also added an external transmission cooler.

[mvmcali]

thanks. thats kind of what i was figuring too. did you run thru the gears while you were doiing it to make sure all parts of the transmission get used?

one thing though based on my understanding of how the transmission/torq converter/fluid pump work... if you are pouring new fluid into the dipstick, that new fluid might be going pretty close to the output hose that heads to your bucket. im thinking of popping only the hot side of the cooler line. now you have 2 'ends'. dump the hose into the bucket and then run another bucket of the new stuff into the 'now available' cooler inlet niblet. this way you know you are really flushing out the whole loop. does that make sense? ... I havent done it yet i just want to make sure im not doing anything stupid

[BubbaFL]

I did not run it through the gears. I was satisfied with the amount of fluid that came out.

My understanding is that the pump picks fluid up from the pan, pushes it through the transmission, out to the cooler, and finally it's dropped back into the pan. You need to fill through the dipstick because there won't be any suction to take the fluid up the return line.

[mvmcali]

if the flow is like you say then yes, filling thru the dipstick (i guess it goes to the pan?) will mean you are putting the new stuff as far from the discard hose as possible... thats a good thing. did you see the bucket go from dark to good very abrubtly ? how many quarts do you think?

you make a good point about lack of suction but i was just planning to have a jug of the new stuff elevated above the radiator with a plastic tube to the cooler input. dont you think the fluid will flow ... #1 because its higher up, #2 because there should be suction because its a closed loop? actually that last point im not so sure of.. pumps like my pool pump seem to have suction (vacuum) on the input side as well as positive pressure on the output side . do you think i have this wrong about the transmission pump?

[yeldogt]

I did a simple drain and refill ... fluid was clean .... simple refill to refresh additive pac in trans fluid

[macgiver]

Ya better look at YOUR transmission's fluid diagram , cause just for your information , fluid from the cooler may be substantially NEEDED to go DIRECTLY to LUBE something IMPORTANT !!! And not to be DUMPED in a pan.

[mvmcali]

Ya better look at YOUR transmission's fluid diagram , cause just for your information , fluid from the cooler may be substantially NEEDED to go DIRECTLY to LUBE something IMPORTANT !!! And not to be DUMPED in a pan.

the problem is i dont think its possible to be sure how the fluid flows from one thing to the next... thats why i was planing to insert the drain bucket and refill bucket into one locatoin only (the cooler input nipple... yes i said nipple .... this way im not interrupting fluid flow... the only thing im not sure of if the refill bucket new stuff will get sucked in. this all seems pretty simple but im worried because no one else seems to do ti this way

[macgiver]

You sound like a very "Smart Fella" ( and not the other way around) , your "thinking" , SOME don't do that here,
you can do it , your being cautious , your asking and getting good answers , that's how you get'er done.

[mvmcali]

coming from a guy named macgiver... i'll take that as a complement
im gonna go for it, i'll post about how it went.

btw - i changed my own oil today for the first time ( i think i last did that when i was in college) and as much as i tried to plan ahead... i had 3 oil diff filter wrenches and NONE of them fit the new oil filter. i ended up tightening it by hand and leaving tomorrow morn for the long weekend. hope i dont spill my guts out there on a california highway. metal on metal is not a sound i want to hear

[mvmcali]

coming from a guy named macgiver... i'll take that as a complement
im gonna go for it, i'll post about how it went.

btw - i changed my own oil today for the first time ( i think i last did that when i was in college) and as much as i tried to plan ahead... i had 3 oil diff filter wrenches and NONE of them fit the new oil filter. i ended up tightening it by hand and leaving tomorrow morn for the long weekend. hope i dont spill my guts out there on a california highway. metal on metal is not a sound i want to hear

[AlanAZ]

I did a return line flush on my QX4, as the fluid started turning brown and I wanted to remove as much of the old fluid as possible, using a method documented on the Internet:

Drop and fill what is in the pan, measure how much was dropped, fill with same amount; add more 1 qt, have friend start motor (about 4 sec.), pump out 2 qts from return line into a clear container (old 1 gal, stiff plastic water containers work well) with 1 & 2 qt marks, add 2 qts via dip stick pipe, repeat until the total new fluid approaches 9 qt, then start adding and pumping 1 qt until fluid pumps clear; after last pump out, top up in 1/4 qt increments until shows full on dip stick, you can do this over several days to get a accurate readings, cold readings are easier to see the level on than hot. The evening before, pull and wipe the dipstick, insert but leave several inches from fully in, next morning, do NISSAN documented ATF level procedure, push dipstick fully down, pull slowly and you'll have an accurate cold reading. (when I got my QX, the trans had been overfilled, I had to twice remove fluid to get it to the right level.)

Tip: when doing the pan drain, fully floor jack the frame diagonally opposite of the drain hole to remove the most old fluid as possible, and let drain until it stops -- I got close to an extra qt this way. As the fluid remaining in the bottom of the pan will mix with the new ATF, and will remain in the trans after the flush is finished. Use a new copper crush washer when buttoning up, I believe it's same as the engine oil drain washer.

I used Valvoline ATF, and added a Magnefine ATF inline filter to the return line, since the trans has a screen and not a true filter. I changed the 1st one at 20K miles, subsequent ones will stay in for 40K miles.

[mvmcali]

thanks for the tips. i think when you say drop and fill you are NOT talking about dropping that pan? I plan to replace the internal filter AS WELL AS flush all the fluid. im wondering if I
1 should drop pan first to install filter, in this case, i will have to waste a couple quarts of ATF to refill and then immediately flush the whole system
or
2. do the full flush first and then drop the pan/replace filter. in this case, im still wasting a couple quarts of ATF but at least im not pushing the old fluid thru the new filter

anyone have any comments?