Beefing up A500 overdrive

Once upon a long time ago, I put too much fluid in a trans; because the stick was wrong, which I did not know at the time. The spinning parts in there musta whipped the fluid up pretty good and some of it blew out the vent. Eventually it "sorta found it's own level". Sure made a mess tho.

BTW
In Neutral, anybody can turn the driveshaft, whether or not the engine is running, even counter-rotating (engine off) ..... think about that. Obviously, at idle, the back half takes a lot less than one manpower.
On the bench, you can easily turn the front half with a plier.
But, I guess, Powering up the pump will take some power: can't be much tho, cuz even the smallest slanty will idle down to~450 in gear..........
My guess is that the power-loss gets sucked up in the TC, which is slipping all the time, converting horsepower into heat. can't be much tho cuz I have run my 904 without an oilcooler 3-seasons ........ with a 2800 .......for five years. And after that, it ran fine in my son's truck for another 5 or more, without a freshening. In the truck, tho, we plumbed the cooler in.
The only thing in that trans, that has to be and stay immersed, is the VB.