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Shimmy / unstable feeling at freeway speeds

Mike Junior

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Hello all,

I’ve had my ‘21 f150 xlt 2.7l for a few months now and have around 4500 miles.

Right from early on I realized that the truck has a very unstable / shimmy feeing on the freeway occasionally. Really more often than not though.

It’s mainly when driving in a straight lane, and it feels like the truck shimmy’s back and forth. Almost like a strong head wind is pushing it all over, but it won’t even be windy.

There is no shake or feedback in the steering wheel when it happens. And nothing in the front end seems to be loose.

I thought the tires could just need to wear in, but after 4500 miles there’s been no change.

My other theory was that the front air dam lowering is causing more wind resistance and/or a weird aerodynamic effect.

Anyone else notice this or have any ideas? My 2018 f150 was super stable at any speed. I’m a bit disappointed.
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psambrose

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I don't have this problem. Have you checked the obvious? Lug nuts tight, proper air pressure in all tires, tire defects, etc?
 

imnuts

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Any modifications you may have made to affect the suspension/wheels/tires?
 

Pedaldude

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Sounds like an alignment issue, one possibility is improperly set toe. Most cars and trucks will have a tiny bit of toe-in (negative toe) for stability. If they are set with zero (neutral toe) or toe-out (positive toe) they can feel very unstable on the highway. Caster angle can also cause the same symptoms. Like when you have the shopping cart with the messed up front wheel that acts crazy.

I test drove a SuperDuty that had a bad front alignment and it felt super squirrelly on the highway, almost dangerously so. When I got out of it, I could smell the front tires and you could feel how much hotter they were than the rear tires by just feeling the sidewalls. I was pretty adamant about the issue to the salesman and they did wind up having to adjust the front axle.

If anything, the front airdam helps stability but definitely check the obvious, like air pressure and the lug nuts. Though, the TPMS should warn you about the pressure and if it were loose lug nuts, your wheels should have fallen off by now after several thousand miles. A bent wheel can also be possible, though normally that would cause the steering wheel to shake, but I don't know if that's true for the newer electric power steering.

If I had to guess, it would be improper toe, maybe caster. Either way, it's a simple enough fix for the dealer. Have it looked at soon, since it's a safety issue and it can also negatively impact tire wear.

Good luck!
 
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Mike Junior

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No modifications that would cause this. All I did was floor liners and bed cover.

I took it to the dealer to be looked at. They say they put it on the alignment rack and it was within spec. Their only suggestion for next steps to to schedule an appointment to drop it off and take a loaner vehicle, so that they can remove the steering rack. Just what I want to do with my brand new truck

I rotated my tires to see if that would change anything. Cant say for sure yet if it helped and will have to drive it more.
 

Pedaldude

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I took it to the dealer to be looked at...
Did they give you a printout of the specs and what your truck's numbers were?

Ford F-150 Shimmy / unstable feeling at freeway speeds 0E35695F-57F2-480A-AA20-B1BE3A997BD6
Ford F-150 Shimmy / unstable feeling at freeway speeds 5C513983-CBF9-46AB-9DDA-8AA761E3CF54
Ford F-150 Shimmy / unstable feeling at freeway speeds DABBE58B-5E81-4C6D-833F-35FCAB97537B


Because, while it sucks to think about it, especially when it comes to a safety issue like an alignment, some dealers are scumbags and will spend more effort avoiding to fix an issue than expending the costs and time to fix it.

The dealership I bought my truck from couldn't even fix the alignment of my doors and spent months and several visits just bullshitting and gaslighting me about how Ford is working on the issue and that I'm 'on the calendar' for what should be a simple issue. Though maybe they were just completely incompetent, since I have a copy of an email from a Ford regional service engineer saying that they have to adjust the hinges and brand new doors wouldn't change anything, because that's what the dealership says was wrong with my doors, that either they or the cab were the wrong shape! I took it to the next dealership closest to me and they fixed my doors in less than 15 minutes.

Long story short, I wouldn't trust what any particular dealership said and if they claimed that there was nothing wrong with my truck, when I knew there was, I would visit a different dealership.

For something like an alignment, I might even just visit an alignment shop to just have them printout what the current settings were.

Then if the alignment truly is in spec, take it from there and look into other possibilities, a bad steering rack is potentially very dangerous and I think there's already been a recall for certain ranges of VINs. I wouldn't worry about having to have it replaced if it needed to be, since it's a serviceable part along with all the other suspension and steering components. I would only be concerned with if it actually needed to be replaced in the first place.

Another possibility, while remote, is that the rear axle is out of line with the truck and if the technician wasn't paying attention, they might not notice because the static numbers might not look very off, when driving down the road, the entire rear end could be what they call 'dog tracking.' One way to check this out is to have someone drive behind you on a straight road.

Ford F-150 Shimmy / unstable feeling at freeway speeds BD526123-CBD9-47BF-9F1E-8B5388BFC7C1


Good luck!
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