Whats the theory behind installing the filter on the cooler inlet line?
It catches and removes the debris before it settles in the cooler. Most transmission failures are due to a partly to fully blocked/plugged trans cooler. Even after a new trans has been installed and fails again 20 - 30 k down the road , it`s because the cooler was not properly flushed and flow tested.
I have seen trannies fail in as early as 500 miles because the cooler is obstructed to the point it does not flow a glass of varsol under 10 psi. in 1 min.
Think of it this way, the shit in your trans fluid has to go thru your trans out of the trans , thru the cooler and be then returned to the tank (the pan), chunks /debris and whatever and only then is it kinda filtered and goes thru again. so when you remove the pan and go WoW look at that shit, there is more in the cooler that is like cement.
Flushing a cooler must be done in both directions and repeated until it is clean and free flowing.