I'm 99.9% sure its the top hose. What you can do is disconnect the top cooler hose and hook up a short piece of hose to the top of the cooler and put both hoses in a jug. Now have someone start the engine and see which hose the fluid comes out. By the way, its NOT high pressure.
Drain fluid out of pan. Measure how much you drain and mark it LESS 1 qt on a clear container. I used a clear plastic Ozarka gallon jug.
Fill the transmission with the same amount you emptied (probably 4 qts)
Connect the outlet side hose (top one I believe) to a 3/8 splice double barbed fitting and about 8' of 3/8 clear hose. Take this hose and the container with you into the front seat where you can start the engine. Start the engine and shut it off about 1" before the fluid gets to the line. Refill transmission with what you pumped out (probably 3 qts). Repeat until fluid turns bright red. Best I can recall it took about 18 - 22 qts. When its flushed out it will almost instantaneously turn bright red (usually within 1 or 2 qts). I have done all my vehicles this way. The only difference is if the vehicle has a paper filter, I change it. The LandCruisers and Lexus have screens, don't bother dropping the pans. Takes about 30 minutes, 1
job. The original write up is in the 80 section under transmission fluid exchange.