This came up in an earlier post in the 92-99 forum.

It seems like an area up for debate.

It seems like an old school thing to use ATF in you PS Reservoir. I know of a few vehicles that actually called for ATF in the PS reservoir. But I think those pumps and equipment were designed specifically for ATF.

Ours Arn't. I don't feel that they're interchangable. It has long been my understanding that, while many people claim ATF is appropriate for use in the power steering system, it is not meant to be there. While both fluids are mineral oil based, the additives (anti-foaming agents, anti-oxidants, swell agents, etc.) really make a difference. Topping off a low PS system with ATF won't hurt, but at some point the concentration of PS fluid will drop too low (if you keep topping off).

I've concluded that ATF will cause the PS system to overheat, cook the neoprene o-rings thus leading to leaks, and cause the power steering pump to wear out prematurely due to abnormal heat expansion of the moving parts. Power steering fluid, on the other hand, is designed to absorb and carry less heat, thus protecting those parts in systems that were designed for that product.

This is all just my opinion of course. There are arguements for both sides all over the web. Please share all of your thoughts.

My only information is from a dealership trained mechanic that they are close enough to be interchanged if you are in a bind. (In the case at hand..the system had a leak)

As a normal practice..they are called different things and probably have different additives for seals etc.

im pretty sure that on the trucks at work we sometimes interchange the two...but those are huge diesel trucks!!

ATF only in a pinch...the friction modifiers in ATF make for accelerated wear of components as ATF has less lubricative properties...as for antifoaming agents both fluids are very similar...ATF has more detergents than PS fluid

when i change stuff part of the charge is rdrainign the old fluid and flushing with ATF blow everything out, install the new pump (or component) and flush with PS fluid then fill with PS fluid...this is of course if there wasn't a catostrophic failure...if shrapnel is in the system...sorry but i wont do the work without getting new lines/rack and pump...too many times has it come back to bite us down the road...and in the end the custome NEVER saves money...it cost more

then again if more people did PM...this shtuff wouldnt happen as often...
I flush my coolant/PS fluid on my vehicles every two years...and the brake fluid once a year

if you are going to use ATF is a PS system i heavily recomend you use chrysler ATF as it has alot less friction modifiers than the dex/mercon III or IV once the leak is repaired...flush the system and refil with PS fluid

Thanks for the insight 400sbc!