The ATF pump has a pickup in the sump(usually near the bottom of the pan or case). There is NO vacuum from the cooler line since the transmission isn't perfectly sealed.
There is plenty of pressure to drain the ATF from your cooler hose with your engine running. You will still need to shut the vehicle off and refill through the dipstick. I usually need to do this once using a 1-2gallon increment and not the silly time consuming restarting/shutting off 1-quart increment.
There is plenty of pressure to drain the ATF from your cooler hose with your engine running. You will still need to shut the vehicle off and refill through the dipstick. I usually need to do this once using a 1-2gallon increment and not the silly time consuming restarting/shutting off 1-quart increment.