Something that happened to me with my new-to-me 03 Caravan ... just bought it and then the PS pump started to growl .... so I grabbed some PS fluid ...maybe 1/2 a pint .... everything is fine.

I did find out later it was supposed to be ATF4 ..... but again .... no probs so far.

I changed out a $400 power steering box on a 1970 Chevy 10 ton dump. I didnt know what the recommended fluid would be. But right there on the Pumps cap, it was Stamped ATF or PS fluid.

I always use ATF, never had any problems either.

Well I talked to the crew at Firm Feel and they said that running good quality ps fluid is not a problem for their pumps. They did bench test it with a atf and mobile mix and they run that in all their cars for years. I don't remeber what the oil ir wt was as I had a few drinks after the job was done and the the box was already in.

I beleive with new box with new seal would go either way. Once the seals soak up whatever oil was used first, that's probably what should be used in it. Power steering, ATF of special mixes will will be for diffrent units, so best to use what your comfertable with.