Just last week, I removed the PS pump to repair leak (large O-rings). I did extensive research on this site and found that the general consensus is to use just plain old off the shelf power steering fluid, as it is most closely like the original ATF recommended back in the 70's and 80's. I use Valvoline (clear) PS fluid. A smaller group recommends Type F transmission fluid, as being close to what was originally specified. Lesser numbers stay with ATF, either regular or synthetic, since the manual specifies ATF. Myself, I relied on the fairly consistent recommendations of very knowledgeable and reliable long standing contributors to this site who recommend regular clear power steering fluid.

You don't have to worry about incompatibility between ATF and PS fluid....they are compatible...just flush away. I flushed with two gallons...yes two gallons of PS fluid, trying to get the red stuff out (I previously ran Redline Synth. ATF), wanting to see pure clear fluid in there. AFter driving for a week, I still saw a pink color...I knew this was just fine, but being the nut that I am, I flushed it again with yet another gallon of Valvoline PS fluid.

Yes, I also replaced the filter in the pump with a new one.

In my case, I don't belive the redline ATF caused the large o-ring seals to leak...instead, it was the build up of corrosion of the alloy pump housing around the exposed portion of the o ring around the edges of the back plate...the corrosion (aluminum oxide?) pushed/distorted the o ring causing the leak. I brushed this groove out, cleaned with some PS fluid, wet the new o rings with PS fluid, cleaned the contact edges of the back plate with fine steel wool, and put back together...now not a single leak.

Good Luck,

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)