Question on trans flush ?

[LAGA]

I am a true believer in doing transmission flushes on my vehicles. I have a question about the method of pulling the line to the trans cooler. Does the fluid come out of the trans after it goes through the torque conv and other internals, or does it get picked up from the pan and pumped out first? It would make a difference in how much of the old fluid gets replaced. And would it be the same on all trannies?

 

[RF Overlord]

I can't speak for other transmissions or transaxles, but in my Ford 4R70W (used in Crown Vics, Mustangs, F-150s, Econoline vans, etc) the fluid runs through all the internals and the TC before going to the cooler, then finally back to the pan.

 

[unDummy]

Its not the same on all trannies. Remember to post the year/make/model/transmission/.... when asking a question. There are thousands of members here and some might have 1st hand experience with your vehicle type.

Pulling the cooler line method, on a hot transmission, will remove most of the ATF if enough ATF is used. Most flush machines splice into the cooler lines the same way. I'm one who remembers the older ATF flush machines that hooked up to the ATF screen/pickup in the pan(pan removal required), and the mess that it made when running the vehicle during the flush(with no pan).

ATF through the cooler in most transmission is wasted fluid. Typically, the ATF is picked up at that pan, worked everywhere, and the leftover goes to the cooler(usually exiting the TC). If the cooler gets clogged or restricted(thermostatically or by fluid viscosity) the ATF pressure regulators waste excess PSI back to the pan.
Its good to backflush the cooler once in a while or install a filter prior to the cooler. Newer coolers are less likely to clog. Some of the older ones had thimble screens or small passages that could clog.

 

[LAGA]

I take care of 6 different vehicles in my family, so my question really was not specific to one vehicle. I do my own flushes by pulling the line that runs from the cooler back to the trans. I was just curious how the plumbing of the trans fluid worked because if it was pumped out of the pan into the cooler, it would take multiple small changes to obtain a good flush.

 

[Michael Polutta]

OK - then I have a vehicle-specific question.

I have a 2003 Honda Odyssey w/ the 5-speed auto. How would I set this up to flush it completely myself? (The standard Honda way replaces 3.5Q out of an 8.3Q capacity.) Does the cooler return line have a vacuum on it that would pull fresh fluid in? Or does it have to be pumped in?

 

[deepsquat]

some methods have you start the engine ..with the line in a bucket, and a funnel at the fill hole ..and as it is pumped out you fill it up ...you should se a color change when it is all the way filled with fresh fluid ..have someone in the drivers seat to shut er off

 

[unDummy]

Start by using the ATF drainplug if equipped. Drain/refill the tranny.
Disconnect cooler line(you'll learn the hard way to figure out pressured side). Aim into bucket. Start vehicle. Pump out measured amounts(1/2 gallon increments) to prevent pump running dry. Shut off engine. Refill and repeat as needed(usually purchase ATF amount 50% over tranny capacity for full thorough flush).

I don't recommend filling at the same time as pumping out. Your funnel will not keep up with the AT pump. And, its too much of a hassle. I can flush just about any transmission with a helper in the drivers seat, without a helper trying to add ATF through a funnel, and without a helper aiming the old ATF.

And, for all vehicles, the AT pump picks up ATF from its sump. There is NO vacuum at the cooler lines. Its just like your garden hose. If you cut your garden hose in half, the handle nozzle side doesn't produce any vacuum.

 

[Michael Polutta]

After the oil-jet-recall on the Odyssey transmission, I cannot fill through the fill plug/hole anyway - I have to fill through the dipstick. SSSLLOOOOOWWWWWW.

It does have a drain plug - 3.5Q will come out that way. The Honda protocol is a drain and refill 4 times, with a short drive (or a shift through the gears, at least) in between.