Transmission flush and return line identification

So, I will drop the pan, replace the filter and gasket and bolt it back up. Refill with fresh fluid. I already have the transmission cooler lines [out (or hot from transaxle) and return (or cooled from radiator)] disconnected because I have a new radiator on this car. I will, then, insert the out (or hot) line into an empty container and the return (or cooled) line into a a fresh fluid-filled container, start the vehicle and let it run until the all fluid through the out (or Hot) line runs clear. I will forget about the use of a machine. Once I am done, I can take it for further inspection and or future Power Flush at Shell, Firestone or comparable Transmission Service Center. Thanks for the additional info regarding the cooler lines and potential damage.
James

Hello there, I just wanted to tell you about the transmission flush and how it went. I know this has been a while but here it goes. After following all the directions you provided and whatever I could find at my disposal, something unexpected happened. I tried to be prepared as you mentioned for just about any case scenario, but what happened was that the transmission return line did not suck up any fluid. Luckily, I had changed the filter and gasket and after sealing and bolting the pan back up, I add 3.75 quarts of fresh fluid. I placed a large Mirror up front and sat in the driver seat ready to start the car and to cycle the transmission. It took 3 seconds to see fluid come out into the empty bucket and could not discern any suctioning. Instantly! Engin Off! I checked things out and made some adjustments, checked the fluid level in the pan (almost a quart immediately disappeared, so I replaced that) and started it again: same thing! Instantly! Engine Off! I Replaced what came out with fresh fluid and continued the pattern. Checked the fluid after 12 seconds: Gone but the tip of the dip stick. The empty bucket now has 2 quarts for a total of 3 quarts in 12 seconds. I refilled the pan and continued draining 3/4 to 1 quart at a time and replacing what came out each time. A total of 24 seconds to replace all. Because of the stress level I went through, I somehow lost track of the exact final amount in the transmission after cleaning up and hooking the cooler lines back up. So, I left it alone for an hour and then returned to check the level: It was half to 3/4 full. "Why?" I asked myself: I made sure I was spec. Could it have been that the Torque converter and transmission needed more than 6.3 quarts on dry? But I did not collect more than 6+ quarts at 100% clear fluid at the end of this unexpected procedure? It seemed to me that I was putting in more than what I was collecting. Really strange. At any rate, I was relieved nothing went dry, I added little over half quart and checked the level: over-filled by a hairline. So, What I am wondering here (and please forgive my lack of experience with transaxle fluid replacement) does the transmission pump push fluid though the torque converter and that fluid having had momentum recirculates into the pan? If the answer is yes, then there could be no suctioning at the return line at all. I searched through a forum debate dated April 2009 where a group of mechanics exchanging stories about how risky some of these procedures were, and here I paraphrase some of them: "there could be no suctioning at the return line with Nissans. You have to do the DIY Flush 'one liter in; one liter out until all finished." Then there was arguing about air entrapment due to this method. And the discussion ended with the claim that Air entrapment in automatic transmissions isn't possible with some responders in that forum agreeing. I could not find any additional search results anywhere else. So, that was that. I hope you're having a good new year.

James

You diagram is an outstanding portrayal of the procedure. Thanks. And yes, that was what I ended up doing (return line that was coming out of the cooler going to the transmission pan is now deeply submerged in a container lifted up to the level of the cooler and filled with 4 quarts of fresh transmission fluid and carrying it out to the transmission). However, the line coming out of the transmission into the cooler I did not disconnect. Instead, I let the old warm transmission fluid flow through the cooler and then flow out into a hose I connected to the other end of the cooler and into an empty container (the idea was to flush the cooler on the way out).
That return hose I also had to extend to reach the container but it developed a pich (bending) in it when I looked at it later, so I am not sure if it collapsed at the very beginning. The other possibility (more likely in my case, and I have to say I got lucky that I did not keep it running for more than 1/2 quart at a time) would be exactly what you said 'an air lock or barrier' an empty space in the pan which would've prevented suctioning: meaning my sister must have been driving the car (before she gave it to me to work on it) with 4 quarts of fluid not 6.3. So, the pan was emptying very quickly and there was no way for me to measure the total amount. In fact, I ended up adding two and a half quarts of fluid after the procedure was done. I took it out after the flushing for a test drive and the car was driving with very good shifting. It isn't slipping intermittently she said afterwards. That's what made me think that she didn't have enough fluid and the TCC was acting up on her. Now, it is working great. Thanks for your help. Thanks for the excellent advice I got from you.

James