I had this in the Excursion section but never got a positive answer. After I make a left or right turn sometimes when I go to straighten out the wheel is offers some resistance and a little hydraulic whine and the when it gets straight it goes into a voilent wiggle. You can watch the wheel shimmy back and forth by itself and there's no way to control it other than stopping and turning the wheel back and forth a few times.(Then it usually goes away). It has good ball joints and tie rods. It's not the tires. Not a loose part wobble. The 4WD works fine and the front u-joints look and feel good. I was thinking it could be the steering box but others have replaced it to no avail. I tried different settings with the box adjustment screw. I changed the oil in the PS pump a while back. Now I'm thinking it's the PS pump or something to do with the front u-joints even though they are free all the time. I am really baffled and don't want to just start replacing things until I hit on the fix.....Gas V-10 Excursion. (Should be same as SD Ford)

 

You have diesel or gas engine? What's everything you done so far?

 

Gas V-10. Nothing done except new ball joints a while back (fine), some experimenting with different steering box settings, and replaced the oil with Mercon V a while back. Tie rods, drag link, etc are all good.

 

We had a similar problem on one of our fire trucks and the mechanic replaced the steering stabalizer never had an issue since. I still think there was something else going on. but it was amazing the diff. from violent shaking especially down hill to total control.. that was 3 years ago.

 

If you have a steering stabalizer remove it for a while and see if the issue goes away.

 

But how could that be it when it only happens once in a while and there is nothing in it that would pull violently at low speeds back and forth? It's just a damper.

 

I had an issue identical to this on an 88 F-250 4X4 a few years back. Well, ok, a lot of years back. On that one, it was the steering gear box. It had a valving problem that would make it dart around for no apparrent reason driving down the road at most any speed. It took me a long time and a lot of research to figure it out, but once I replaced the steering gear the problem went away.

 

Thanks, I was thinking it was the valving in the PS box and I might just change it. I guess you need a Pitman arm puller to pull the arm. What throws me is that some people are reporting that they changed it and nothing changed. I will wait a little while longer. Did it do it just once in a while? Of course the box was probably a little different.

 

At low speeds usually you are steering at a large angle. If a steering stabilizer is damaged or just plain bad it can cause the steering to lock since it moves in and out as you turn the wheel. If it locks it takes a higher amount of force to free it and once it pops loose the steering wheel jerks.
Now I'm not saying this is your problem but it sounds like it could be part of your problem. Altought the wooble does not sound like it's caused by the stabilizer. But it's easy and free to try before you go through the expense of replacing the steering gear box. If you still have the issue after taking the stabilizer off then you can move on from there.

 

It doesn't just jerk. It keeps going back and forth like that until you stop and move the wheel back and forth a few times.

 

I had a 84 chevy ton that would do that. You hit a bump just right and it would shake so violently that you had to come to a stop, or like you said give the steering wheel a few complete cycles. I replaced the steering damper(stabalizer) and that took care of it. Now I have a 2000 F-350 dually that once in a while did the same thing. For about 40 bucks it took care of the problem. I noticed that with both stabalizer's that i pulled, if i let it set for a few min's i could easly move the shaft in and out about a 1/4'' by hand. But when i fully stroked it then tried to jerk it in and out I couldnt; worn internal seals? Dont know, you be the judge of that. Hope this helps in any way possible, i will keep in eye on this to see where you decide to go with it. Oh by the by my 84 had a 9' plow, with the plow on it was worse. The 2000 ford is a dually also with @ 316k on her, all ball joints and linkedge is solid, been replaced but still true!

 

Sounds like you are due for a steering stabilizer anyway... try that first as they dont cost much and are easy to install.

 

I would replace the stabilizer anyways for starters. From what you're describing, it sounds like the steering box but could also be the pump going or both. Replacing the stabilizer will help. If I had to choose one of the others to replace, I'd start with the steering box and go from there. The whining you're hearing is probably coming from the pump.

 

Thanks. I'll replace the stabilizer for starters. The strange part is that I can go 2 or 3 days before it happens sometimes.

 

I did a little digging and found two articles that may or may not help but worth a look:

Ford 01 Excursion Power steering problem - ThumperTalk

HAVE AN 01 EXCURSION, V10. HAS A STEERING PROBLEM, DONT BELIEVE - JustAnswer