I've got an early email to someone that seems to know a lot on p/s fluid, but in case the forum is better method, I thought I'd post the same general question.

Just replaced gearbox on 67 p/s system.

Many here seem to post that you shouldn't use current ATF in p/s system, recommending the GM P/S Fluid.

IS THERE AN ISSUE WITH MIXING? I can drain much of the ATF, but I know there will still be some in there.

If mixing is problem, how do I totally drain?

On other hand, should I just go back with Dex III, and be done with it?

Thanks,

What I would do is take a suction gun and suck out the fluid, and replace it with PS fluid.Then disconnect the hoses, and put the ends in a container, and have someone start the motor, and turn the wheel, and pump out the fluid, and keep adding till all the old fluid is out. If you don't want to remove the hoses, I would start the motor turn the wheel back and forth, and then suck that fluid out. If it still looks like there is still old fluid in there I would repeat the process, I would think two times would do the trick. I also think a little of the old fluid would not be a problem.

I cannot answer the question about mixing the two but I've had ATF in the PS system of my SS for 12 years with no problem. That's what was in it when I bought it. I bought a new boat in '83 that had a Mercruiser IO with a 350 Chevy engine and power steering. It had ATF in the PS system from the factory (Mercruiser). PS fluid is probably better but ATF will certainly work.

The recommended ATF at the time was type A. it's still available.

fwiw, we used to use atf all the time, never had a problem, got it in my 70 now.

I use PS fluid in my trans and ATF fluid in my PS. As long as you're using the correct type (Mercon, Dexron, F, 7176) it won't matter.

fwiw, we used to use atf all the time, never had a problem, got it in my 70 now.

My '70 factory Service Manual says that you can use either power steering fluid or ATF in the power steering. I have always used ATF, even in my daily drivers because I live in a cold climate. Power steering fluid gets hard as a brick in cold weather and blows PS hoses. ATF flows well at low temperatures, so I drain out the PS fluid and replace with Amsoil synthetic ATF to save the hoses over the long haul. It has worked for 40 years so far.