Wow! Quite the timely thread, as I've been hearing a similar noise from my 84.
I probably did this wrong, but here's what I did last night.
Removed the cap to the reservoir and then started the car. I had noticed the ATF fluid seemed a bit low, before starting it, so I filled it to the neck.
After starting it, I let it run for about 10 minutes, just to let everything warm up. Once warmed, I started to turn the wheel to the left, with the intent of taking it all the way to the left lock.
Almost immediately, I got the groaning noise and foam flowed from the open reservoir like lava from a volcano. I literally had to move the steering wheel just a little bit at a time in order to keep this from happening. Even little bits of turns would cause the foam to rise, so I stopped turning the wheel as soon as I saw movement. It actually took close to 30 minutes to get all the way to the left lock.
Once I made it to the left lock, I held it there for about 30 seconds and then started back towards the right lock. Surprisingly, there was not much groaning on the way back to center. Once I passed center, however, the groaning started again, but, it wasn't quite as bad on the way to the right lock. I think I got to the right lock in about 15 minutes.
I spent the next hour and a half or so going from left lock to right lock, each time, it seemed to produce less and less foam. I was able to get it to the point where I could turn fairly quickly from one lock to the other, with almost no groaning and/or foam...almost. If I slowed down with the turning, the groaning would return, as would the foam...simultaneously. I get it, groaning = foam!
John_AZ, after seeing your post above, I believe my next step will be to follow those instructions, starting the car and turning it off immediately, as I'm sure there is still quite a bit of air in the system.
Randy