I did this yesterday on my GX470. I put 3/8” clear tubing into the fill port on the side of the tranny. I ran the tubing to the right side engine compartment and used one of the cheap screw on pumps to pump fluid into the fill port. I disconnected the tubing above the cooler in front of the radiator and another clear tube from here to the milk jug. I ended up exchanging 15 quarts of Max Life through the system. The last two quarts were as black as the first three that I drained from the pan. Does this really do any good? Aren’t we just pumping out the just pumped in fluid ? I cycled the truck through the gears a few times when draining into the milk jug. Should I have left the truck run a few minutes before draining and adding again ? I didn’t see any difference in the color of the fluid when finished. It was still black after exchanging 15 quarts.
I think that you must have done something wrong. I would suggest you carefully look at the procedures in the original post. I can't think of exactly *what* could have gone wrong, since it appears that you are saying that you exchanged 15 quarts of fluid, and that ALL 15 that you pumped out were black.
Maybe you disconnected the wrong hose ??? Maybe you weren't pumping fluid into the fill port??? I'm not sure of the problem, but my biggest concern is that you say that your transmission fluid is black. That's not good. After I did this transmission fluid exchange method, my fluid looked absolutely brand new.
If you *did* do the exchange properly, maybe your transmission is really *that* dirty? Were you running Toyota-WS transmission fluid before you started the fluid exchange? If not, maybe whatever was in there behaves differently from Toyota-WS fluid, and maybe there is lots of dirt, and that's your problem.
I'm not sure what advice to give you, because sometimes when a transmission is heavily worn and the fluid is very, very dirty, it's the dirt and sludge inside the transmission that keeps it working. In those cases, sometimes cleaning the transmission and putting in new fluid, removes the dirt and sludge, and causes the transmission to slip and fail.
If you think you're transmission may be *that* bad, then often the advice is to leave it well enough alone, otherwise you might be lighting the fuse on a time bomb... :boom:
Maybe try going to a local transmission shop, if there is one that has a good reputation and that you trust, and ask them for advice and/or help.
I wouldn't want to lead you astray on this one, because a trans rebuild would be very expensive.
Best of luck with this one.
-Phil