At 50 k on a lark I had FPS change my PS fluid. I had plenty of oil analysis kits so we took a sample.
PS fluid ~ AFF ~ very light weight hydraulic oil. Well mine was 30W and 50% oxidized. Which when you burn ATF you get valve grinding compound slurry.
Our PS unit is not Ford, Ford purchased an expensive unit from ZF, It is nice but high dollar to repair or replace. If you drop the front valance you can find a hose with a screw clamp that is a PS hose. It is the low spot in the PS system.
Remove the camp, drain the system, refill with ~ quart of quality ATF of your choice. Do it every 20k and you should never have a problem.
Ford does not have an interval to replace PS fluid. I guess if you had extra ATF you could even FLUSH the system by dumping in a clean qt and letting it run out.
You could lose your PS pump, create wear on the rack & pinion gear. - You could spend a several thousand in repairs. Besides clean fluid is like no sand in the works, it feels nice & light since you are not forcing an abrasive slurry through the works.
I hope that helps,
To: "Timothy Wright" <firstname.lastname@example.org>;
Subject: Power steering [was RE: Newbie 97 SHO owner]
Tim there was some discussion at our recent get together in OKC about the
power steering flush and maintenance. Could you elaborate on the flush intervals
and the consequences of burning up that rather exotic ZF steering assembly?
I just had my steering system flushed at a Ford dealer a little over a two
weeks ago with the cost being $70. I believe they used a Wynn's flush...very
common. A little spendy, but considering it completely cleans the system out and
the cost of SHO steering parts not bad...IMHO
My rule of thumb is to do the power steering as often as you do the tranny fluid...every 30,000 miles or less.
As some of you may recall I had a steering gear go about 100 miles before my factory 3/36 expired. Not a dealer in the U.S., Canada or even Ford themselves had the part. With some help from a region rep, the dealership doing the work had to order a gear to be made in Germany for my SHO. Not cheap to be sure so flush that system!
Just turned 66k
You should beware of getting any air in the PS rack as it needs to be vacuum bled to remove it. FWIW I flushed mine and added Mobil 1 ATF. After a year it looked brand new. I think if you go to a synthetic ATF you will not have any problems. Currently have Redline D4 in as PS fluid on the '97 and Amsoil ATF in the '93 as PS fluid.
To test you PS fluid get a white napkin and put a drop of new fluid on it then a drop of your used fluid. It will be very apparent if it needs to be changed. Same goes for the ATX fluid as far as testing.