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Shimmy in steering wheel

2004 Dodge Intrepid.70000 miles.Shimmy in steering wheel. Seems to come and go at about 7 second intervals.Suspension,tires,balance,alignment all check OK. One mechanic suggested steering rack valve problem.Could the computer possibly have anything to do with the 7 second interval? Thank you.

No doubt your mechanic checked tie rods, bushings, ball joints, etc but they’d likely cause a shimmy all the time. Weird that it seems to have a heart beat…
I wonder if your steering belt is slipping or your steering pump has having some sort of issue where you have a situation where the power steering basically goes on and off periodically. Since you’re holding the wheel, you try to compensate for this, it fights you back when it turns back on and causes shimmy. It could also be that there’s some blockage in the pump or steering rack.
The above is a shot in the dark but maybe make sure your steering belt is tight. You could replace your steering fluid to see if that helps. Those would be relatively cheap things to try.

Thanks for the input RemcoW. I also found that the shimmy goes away on acceleration. Not sure how this ties in.

It narrows it down to your , chassis, drivetrain or tires. My own experience is that an out of balance wheel, a tire with an internal fauklt, or a worn chassis component at any of the articulating joints can set up a rhythmic oscillation. The whee;s & tires can be double checked on a machine that does “road force balancing”. The rest can be checked by any good chassis specialist.

My money is on a worn out tie rod end or ball joint.

That was my initial thought as well but one would imagine the mechanic would know to check for that.
You’re probably right, tho. It seems like most mechanics don’t know where to start unless the car throws a code.

My money is on the steering rack, as far as I know it is a complete replacement, not a valve repair. Hope I am wrong. A good mechanic should be able to diagnose thee problem, try 2 or 3 or even a dealer to get the proper fix.

Thank you all for your comments.An inspection at the dealer found a tie rod end that needed replacing.Had it replaced. Not really any change.The shimmy might be slightly less when braking but not by much.I’ll try to find a shop that does “road force balancing.” I’m still in a quandary about this and the three mechanics I went to so far were not too much help. One suggested flushing the power steering system and if that didn’t work I’d have to change the steering rack at around $850. I’d like to have more confidence before I spend that much.

I seriously doubt of it’s the PS rack. I’ve never heard of a spool valve (the “valve” mentioned in your original post) malfunctioning in a way that would cause a shimmy. You could, if you like, find out for sure by removing the PS belt and seeing of the shimmy disappears. Be aware that your steering will require a lot more effort and avoid areas that might require a sudden evasive maneuver (like residential meighborhoods), but it is a method of checking.

+1 That would be the acid test.

It does seem to point in the pump’s direction, with it going away when he accelerates. Of course, that could be because the shimmy is just higher in frequency and may not notice it as much.
So try this: put the car in first gear and see what happens when you briefly drive it at - say - normal road speed. It’d be interesting to see what happens at higher engine speeds - not higher road speeds. Note we’re not talking highway speeds, of course, but see what happens to that shimmy at 20 mph. If it disappears, the pump may not be pumping well at lower engine speeds. That thing may be on its way out or maybe the fluid isn’t doing the job anymore.

Edit:
Btw, just noticed: that mechanic did look at the brakes and rotors, I hope? You mentioned all the other front end parts but I don’t see brakes. That’s usually the first thing, besides tires, that causes a steering wheel to shimmy (albeit not with that weird 7 second interval).

How about rotating the tires and see if it goes away? A separated belt inside the tire can cause a shimmy.

“Suspension,tires,balance,alignment all check OK” he says.

I had the tires rotated and nothing changed.They did turn the rotors down when I had new brakes put on around 8 months or so ago.I really can’t say if the shimmy started after the brake job or not.I don’t think so or I would have connected the two right then.

Wheel bearings may be flat spotting.

Perhaps, but the reason I suggested what I did was that it would not be the first tire problem detected on a road force balancing machine that didn’t show itself with a regular spin balancing. The tire could still have an internal seperation not showing up on a regular spin machine.

Now that you mention it, tsm, I had a C-1500 that seemed to shimmy at about 45 mph while it was OK over or under that speed. I twisted and pried on every part of the front end and replaced several pieces because they had a “perceptible” amount of play but the shimmy remained. My brother, who doesn’t know how to open a car’s hood, asked my why I was driving on a bad tire. I never could see what he saw but I replaced the tire in question and the problem disappeared. He swore that a weak belt was visible to him(?) Go figure.

Brother got X-ray vision? I’m jealous!
Pass my kudos on to him.

There is a rare circumstance where you have 2 tires that vibrate in and out of sequence because of the slight differences in diameter. In essence, it’s that neither tire has a large enough vibration by themselves to cause a steady vibration, but together they add - then subtract - and the result is a vibration that comes and goes.The shimmy timing seems to be about right for this.

Try moving one or both of the tires to see what happens. If the problem goes away - or doesn’t - then you’ve narrowed down the problem.