The theory was that this would help clean
the clutch plates somehow
Noooooo no no no, that's a lot of garbage.
First of all, "Proper" Transmission flushing is done by cycling Transmission oil
through the trany till the oil
coming out is clean. It is a cheap
skates way of replacing the fluid without removing the pan. Most Tranys don't have bungs on the end. In fact, GM save 1.2Million dollars a year by not including a drain bung. This "flushing" business is just that. A business where lots of money
can be made for very little cure. I doubt very much that the Transmission builders would suggest this method. The Bung is not needed because the pan should actually be removed for one main reason. There is a pick up filter directly inside and this above all things, needs replacing when the oil is discoloured and burnt.
Now OK, I realise the description above is alluding to something quite different again. But "cleaning" the plates of something is not the issue. In fact, the plates being dirty is not really the reason why the tranys stop working anyway.
NEVER ever put any other fluid into a trany. The plates would destroy themselves and will take a partly running transmission to a fully stuffed Transmission in seconds.
It is usually pretty much a case of, if the Trany is worn out, then it is worn out. Cleaning
the plates, even if it did clean them, will not solve the issue. The plates are slipping because the plates are worn out, not because they get dirty.