5R55E Output Port?

[2000StreetRod]

I just read a thread on flushing the transmission fluid on a 5R55E. It stated that when starting the engine, fluid could drain from both ports - not just the output port that connects to the external oil cooler(s). Does anyone know for sure which port (upper or lower) on the transmission case is the output port? A while back I disconnected one line from my oil cooler, started the engine and collected about half a quart from one line. I assumed that line to be the output but now I'm concerned it may have just been drainage and that flow from the real output line was blocked by the transmission internal thermostat.

 

[2000StreetRod]

Question answered - top is out

This morning I set up a test to determine for sure which port on the 5R55E is the output. I disconnected both ATF tubes at a convenient location and connected each to a drain hose going to a container as shown in the photo below.

The engine was cold when I started it and fluid immediately flowed from each hose into the container. You can see in the photo that the container on the right contains almost twice as much ATF as the container on the left. The tube on the right is connected to the upper port on the transmission case.