DIY ATF fluid flush - fluid return lines

[tmontague]

I changed the ATF in my sister in laws '07 Yaris HB today as it had about 280k km on it and I have no idea if it was ever changed. I put in some Valvoline Maxlife fluid as I find it does a better job keeping a low viscosity in the crazy cold winter startups we have. It is also cheaper than Toyota WS ATF.

I wanted to do a proper flush and not a simple drain and fill a few times to hope it got rid of most of the old fluid. There are a ton of youtube vids explaining how to do a flush using the trans cooler return line so I'm not going to explain how to do it. I do however want to post about which line to use so that you don't waste time and make a mess guessing which line is what.

If you are facing the engine bay and you look down you will see a line that exits the radiator on the your left side (passenger side) this is the return line that you want to use. The line on your right (driver side) is not the one you want to use. Disconnect the rubber hose at the end that connects to the hard line entering into the trans. Use something to point the hose down into a drain pan. I used a long pry bar and rested it against the clamp on the hose and the weight of the pry bar held the hose in place. The pry bar was held up by leaning on the front of the engine in the engine bay.

Instead of the hose going into the hard line into the trans it just pumps fluid into a drain pan. For further clarification on the correct hose, the proper hose attaches to a hard line that enter the trans at a low level near the drain pan. The incorrect hose exits the trans much higher up which is where the trans pumps sit and it pushes fluid out of the trans and into the cooler.

technically you could use either hose as long as you disconnect the rubber part at the right end so fluid is coming out. However the hose I discussed above is in a good orientation that makes it easy to point it into a drain pan.

Youtube "diy transmission fluid flush" and you will see multiple videos outlining how to do this procedure.

FWIW the old fluid that came out of the trans was still a red color but more of a greyish red. It smelt pretty good and showed no sign of transmission issues. The whole trans holds somewhere around 9L of fluid so a proper flush will take around that so prepare to buy a good amount of fluid.