I have the same problem except I own a 1988 Chevy Suburban, 4x4, straight axle, manual lockout hubs. Everything is new, ball joints, tie rod ends, drag link ends, brakes, rotors, tires, front end alignment ect ect ect ect. The only thing that is not new is the axle u joints and I have one that is dried up but I did not think this was the issue because I have manual lock outs so the u joints are not turning when in 2wd.

I have to second guess this theroy now though because it only does it after making a right hand turn. I made a right to get on the freeway and while stepping on the gas as I straightened out the steering wheel it was like a Ghost just grabbed the wheel and decided to turn it left, then right, then left again and I was swerving all over the place, scary scary *****. It stops just as fast as it starts. It only does it once in a while but always after making a right turn...never a left. It was always at speeds under 30mph...it is not death wobble, that happens at higher speeds after hitting a bump and it is more of a high speed shaking.

I have also been a mechanic for over 20yrs and never seen anything like this. But I am seriously thinking u joints now! The reason why is because even though they are not turning when the hubs are locked out they still need to be able to pivit when turning the wheel.

If a u joint is binding when you try to striaghten the wheel out one wheel will follow the direction of the steering wheel while the other is binding. Then when it is forced (BY the power steering) it will suddonally snap in the direction you was trying to steer, you try to corect the funny feeling in your wheel and it goes the other way...back and forth 3 or 4 times.

How and when does your problem occur? Does it do it after making a turn in one direction like turning right on a street or on ramp? Or does it do it when driving down a straight road?

Mine is only doing it after making a right turn and the speeds have always been under 30mph. It has never done it going down a straight road or on the freeway and it only does it once in a while.

Do you have axle u joints or CV joints? If you have U joints I would seriously think about replacing them even if they appear to be fine to you.

I will be replacing mine this week and I will post back if it fixes the problem.

If it does not fix the problem then I am going to replace my steering box and then the pump its self in that order to try to solve this problem.

However my fluid looks clean, my pump does not make any noise unless I am at full turn and really applying pressure on the steering wheel.

Oh and after making a right turn and then trying to straighten out the wheel when it is almost straight I can feel some resistance in the steering wheel right before this happens. Sound familiar? Then it has a mind of its own and wants to dart all over the road violently.

Post answers to my questions...maybe we can help each other out and find out the exact cause.

Also (I dont know Fords) but is your truck a solid front axle or IFS?

 

I thought this was a Ford thing. Yes I can feel some resistance right before it happens and a little hydraulic whine and then it has a mind of its own and then darts violently all over the road. Yes solid front axle with U-joints. Yes it does it right after making a turn at low speeds and never just starts occurring while driving straight. (better after it is driven for a while). I replaced my fluid and it still does it. Mine doesn't stop as fast as it starts but it will usually stop if you stop and turn the wheel back and forth a couple times. I am thinking it is either the steering box or the pump and I want to find out for sure before I start replacing things as I don't have the money I used to have.

 

Yep sounds like the same thing mine is doing. Now think about it for a minute...what happens when you try to straighten your steering wheel and
one of the axle u joints binds? You would have resistance on the steering wheel while you are trying to straighten it out. And once that tension is released it is violent and your front wheels will go all over the place. The best way I have described my problem to people is to imagine your front tires in two S shaped ruts...the tires follow the ruts no matter what you do with the steering wheel.

Like I said I have replaced everything except u joint, power steering pump and steering box. I was thinking just like you and do not want to replace something I did not have too. Everything I have replaced so far has been over the last 6 months and needed to be replaced 20yrs old.

Now after I replace u joints if that dont fix the problem I am on to the steering box then the pump it's self.

If after all those the problem is still not fixed then I have to start thinking caster/camber angles. Think of it as a shopping cart...you know how the wheels are slanted and if you are pushing a cart in a corner and just let go of it the cart will start to go straight and the wheels will automatically straighten out. Thats because of caster angle...same principle applies to vehicles. Now imagine doing the same thing to a cart that had no angle on the wheels...see where I am going with this? How ever being a solid front axle there should be no way of adjusting this angle without turning the axle it's self...so I just cant see how this could get out of wack?

All my spring perches, u bolts ect ect are tight and in perfect shape. Chevys had a problem with the frame cracking right by the steering box but that was one of the first things I check for.

Will post back with results of u joint change.

EDIT: Did you notice if it only does it after making a right turn or left turn or does it do it either way?

 

It does it either way. I kind of have my doubts about the caster angle theory as it is integral with the spindle and not easily changed and I can go for 2 or 3 local trips sometimes with no problems. Yea it's like someone is grabbing the wheel out of my hands and tugging it back and forth, but I can stop, jerk it it back and forth a couple times and it usually goes away. The u-joint theory is possible because it is that same squiggly feeling as when you turn sharp on dry pavement in low range and in 4WD. So thanks and keep us posted!

 

Yep I am not thinking caster angle right now either that will be last resort if everything else does not fix the problem. And mine is the same way I drive this every day and it will go 3 weeks without doing it and out of the blue I am all over the road like a drunk!

It is also funny that you have mentioned it is worse when it is cold because the majority of the times it has happened to me I have just left my house and was no farther then 5 miles when it does it...and after going on the freeway and driving all day it hardly ever does it. With the exception of last week I drove on the freeway for 30 miles to my wifes work, got off the freeway, drove through the city for a few miles and I made a right turn on a residential street and it did it going maybe 15 to 20mph and I almost hit a parked car!

Everything I have searched for so far is all death wobble on lifted trucks and bump steer ect ect. Never seen a thread on this until I came upon yours.

I am also going to check on Bob is the oilguy forum and see if it is OK to run something like Marvel Mystery Oil in the power steering pump to free up a sticking valve if that might be the problem.

 

I replaced both u joints took it for a drive and it still did it! So I call my friend up who is a Master mechanic and he came over and I let him drive it all over the place until it did it again and it did. He said 100% positive PS pump! So I replaced the pump yesterday and drove all over the place no problems. Then I just got back from a 1 hr drive this morning no problems. I asked him why the PS pump would cause this and he told me when Hydraulic Pumps start to fail whatever they are controlling will jump around...this created feed back in the steering wheel.

This made perfect sense because I have seen pumps going bad in fork lifts before and when you lift something with the forks they would jump and jerk the whole time they was going up. Pumps dont have to be making a bunch of noise either to be going bad!

I will be driving this all week and if my problem comes back I will post back...but I think the issue has been figured out.

 

This is great. When you said you were going to replace the u-joints I thought about it some more but they wouldn't have just acted up sometimes and they didn't explain the hydraulic whine noises. My suspicions rested on either the pump or the box and I've heard stories about people that have changed the box and still had the problem. I think the pump doesn't have enough pressure to efficienty control the steering box and that explains why it is better when it warms up.

 

Has anybody replaced the power steering pump and cured this problem? It seems to be narrowed down to this as there are stories of the steering box being replaced but the problem still exists. This seems to affect GM products also.

 

I have a 02 Excursion with the exact same symptoms. I have perceived rolling resistance (drivers side front tire) when the problem occurs. If it's the power steering pump it could be that the pump is creating additional drag on the engine. This could be perceived as rolling resistance. I think my problem is something else. In trying to diagnose the problem I replaced the front driver’s side wheel hub. With the new hub I noticed that if I turned it backwards it would intermittently grab the axle and pull on it. You could see the axle extend out just a little each time it happened. When this happened the axle and hub would bind causing the axle to engage with the wheel hub (not the 4x4 locking hub) for about a half turn. If this were to happen while driving, the result would be exactly what has been described. I think the problem is somewhere between the end of the axle and the universal joint (i.e. from the tire to the far side of the u- joint.) Anyone having death shake with a 2x4?<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

 

Well,
I changed the vacuum pump last week and have been problem free .............. until today!
The problem returned. I will be replacing the ps pump next week. I need to get this thing fixed! I think we all should start gathering information on the trucks that are having this problem.

My Excursion is four wheel drive with 133,000 miles, 6.0 diesel. Don't know if this problem is on any 2w drive trucks. When I first noticed the problem the first thing I checked was the ps fluid. It was not even on the stick. I poured in over a pint to get it to read on the stick. After filling the problem went away for a short time, but came back. I have had almost all the front end parts that can be changed, changed. I did notice when I removed the front hubs to replace them, I drove the truck and could never get the problem to happen. My automatic hubs did not work all winter and when I needed it, I manually locked them. This is why I drove the truck without the hubs before I replaced. I thought the problem was with the hubs.

The only thing that I have left to change is the ps pump.

 

One of the very first things I tried was removing the locking hubs. Mine was worse without them. After the installation of the new wheel hub didn't change anything I swapped the locking hub with a locking hub from my 2003 Ex. (Wife’s is the 2001 with the problem, I have a 2003) My 2003 is fine with her old locking hub but her Ex started trying to kill her again after about a week. Has anyone replaced the stubby part of the axle? (from the U-joint to the wheel.)

If anyone gets a safe opportunity, let the truck roll with the engine off when the problem occurs. I think that would answer the PS pump question.

Good luck all.

 

The pump is what I have pinpionted. Please let us know if that fixed it. You might have ruined the pump by letting it run so low.

 

I will shut the engine off while rolling as soon as I get an opportunity and post the results.

 

I shut the engine off after it did it today and it didn't stop darting but it was out of 4WD so the u-joints should just be sitting there doing nothing.

I just looked at the u-joints and they look good and have no binding or loosness. They spin freely also. Someone else here replaced they and the problem persisted. Maybe the low pump pressure started the darting and continued in the steering box after I shut it off. I guess I'll have to wait as I don't want to start randomly replacing things like the dealers do.

Bingo! that was it! ............charge them for everything.

 

pitman arm? sometimes they look good and they are worn guess i would have lost money on my guess of the steering box, hade a gmc do this to me reading the post about the sub reminded me