Shimmy - Help, what could be wrong?

[airline tech]

Hi Tim, I did get a 4 wheel alignment when I changed out the front and rear shocks (back in 2021). I did not get a 4 wheel alignment after changing out the leaf packs that I did in March. The truck was running fine up until I took it in to DT to have them put the other set of wheels/tires on.

I would check the rotors and ensure one is not slightly cocked sideways on the hub and or warped.
As this is the only thing that comes to mind, started just after wheel / tire swap and placed old back on - and still present
I am sure if you were to jack it and spin the tire, you would possibly see a side-to-side wobble of the tire as the wheel is not setting truly flush on the hub be it cocked rotor, or the rotor hub surface is warped.

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[dapakattack]

Are all your lug nuts still in good shape? If they are swelling, you may not be getting them seated properly.

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[got3fords]

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[RangerBill]

I would check the rotors and ensure one is not slightly cocked sideways on the hub and or warped.

I was thinking the same thing but found that the rotors are part of the hub casting (not a separate part).

 

[RangerPNW]

I'm leaning towards that darn two piece drive shaft... mine behaved for quite some time after I leveled my truck before it started to vibrate quite badly. How I personally was able to differentiate it from an out of balance tire was the location of the shake, it seemed to come more centrally in the truck rather than at either end. Got really bad when I hit 90 passing someone, the ass end of the truck felt like it was going to fall to pieces. Threw a Tom Wood's one piece shaft on and have been happy ever since.

Might be worth a shot, they're fast to get it to you and they have an excellent return policy if it doesn't fix your issue.

 

[Dieseldean1]

Hello All,

First off I want to thank @Fitzmotor (Mike) for allowing me to take up some of his precious time helping me try to figure this out when it first started. Now, I figured I'd take up the precious time of more forum members.

Ok, here is the issue. Truck has been driving fine for 30k+ miles. This is after adding Eibachs to the front and back (probably at the 7k mile mark 3 years ago) and doing the global leaf pack back in March. Just recently switched out my 17" wheels to an 18" STX set and this is when I started experiencing the issue.

The truck drives like a tire is out of balance (the steering wheel doesn't really shake and it doesn't seem to pull one way or another). Had the STX wheels Road Force Balanced, which showed that they in fact needed to be. Great, that should take care of it....NOPE! Truck still shimmies...especially noticeable in the 55-75 mph range. Ok, wasn't happening on the old set and maybe I got a bad wheel/tire that was causing the issue. Put on the old set last night. Ten minute highway drive into work this morning it felt better....not as noticeable a shimmy...drive home...it was back and maybe a bit worse...now feeling like there is something more suspension related.

I've checked the shocks, the leaves, and the torque on the U-Bolts and all seem to be ok.

I've never replaced the DPFE sensor....could that be it?


Thanks for the help everyone. This is a great group!

If the rotating assemblies are good, check rear driveline.
angles might be too steep- correct with a one-piece driveline.

 

[Jason B]

Can a 4 wheel alignment be done on a live rear axle? I was just at my dealer and asked for a 4 wheel alignment, after noticing the inside edge of the tread on both rears were wearing more, and they told me that 4 wheel can't be done, which I thought was strange. I had the tires rotated about 1,800 miles prior so I assume they were on the front when the problem started. So I got the front-only done. But then I'm also the guy that asked to have the power steering fluid changed in my Mariner. "Uh, sir, it's electric." ?

Yes, you can have a 4-wheel alignment, in fact that's the best way to go. There is no adjustments made on the rear. It's just to ensure the front and rear wheels are running parallel, otherwise your vehicle would have a slight 'crap walk' going down the road,

 

[Chris M]

...crab walk.
Which IS a crap walk for sure!

 

[Jason B]

...crab walk.
Which IS a crap walk for sure!

Ha, I was going to edit that, but I think I'll leave it in.

 

[dapakattack]

Yes, you can have a 4-wheel alignment, in fact that's the best way to go. There is no adjustments made on the rear. It's just to ensure the front and rear wheels are running parallel, otherwise your vehicle would have a slight 'crap walk' going down the road,

The Dealership offers a Thrust Angle Alignment (which apparently they can loosen the U-Bolts to get the axle squared up w/ the frame) which also includes a 4 wheel alignment.

I'm going to bring it in Monday morning and see what they can do.

 

[Ninong]

Rotate your tires and see if those changes anything. Good way to rule out tire/wheel issues. I second/third and fourth for an alignment check.

 

[airline tech]

I was thinking the same thing but found that the rotors are part of the hub casting (not a separate part).

I am talking about this - The Rotor Hub (Hat)
If this is distorted it will cause the wheel not to sit flush (O/B) side and not flush (I/B) side to the Hub Assembly.

Improper Torque Procedures are the main cause of this, and with the OP stating that the issue arose just after wheel / tire swap and then reinstall of original set - with same results leads me to this as a highly possible area of concern.
Sometimes even proper torque procedures can bring this on, it has to do with the memory properties of the metal and the heat that is generated by the braking action.

Warpage in this area does not ALWAYS cause brake pedal pulsation but will cause the wheel to wobble (side to side) when rotating.

Now with that said, yes it could be an alignment issue or driveshaft issue or worn suspension bushing's etc. but with the issue coming on just after swapping the wheels, I am focused on this point as a highly possible point of issue.

 

[TJC]

I'm leaning towards that darn two piece drive shaft... mine behaved for quite some time after I leveled my truck before it started to vibrate quite badly. How I personally was able to differentiate it from an out of balance tire was the location of the shake, it seemed to come more centrally in the truck rather than at either end. Got really bad when I hit 90 passing someone, the ass end of the truck felt like it was going to fall to pieces. Threw a Tom Wood's one piece shaft on and have been happy ever since.

Might be worth a shot, they're fast to get it to you and they have an excellent return policy if it doesn't fix your issue.

I had the same experience at speeds at or above 75mph. The entire truck shook violently, then dissipated as speeds dropped below 75.

Shimmy to me is different, sounds like a loose rim to me. but what do I know,

 

[sbrinkley]

I agree with @airline tech when your new tires/wheels were installed they weren't torqued properly (overtightened) and the rotors are causing the vibration. I would recommend a couple of tests to perform while driving. 1) Drive the vehicle up to speed and instead of using the brake pedal, use the emergency brake to stop. This will isolate the rear vs the front brakes. See if the vibration changes. If the rear rotors are out of round you could potentially feel a vibration (the only issue here is you are squeezing the brake shoes in the rotor hat so it would have to be pretty extensive to feel). 2) While driving at higher speeds and when you start to feel the vibration kick the vehicle into neutral and see if the vibration changes. This will help you determine if a u-joint is causing the vibration. The idea is to just see if you can get the vibration to change. The other option is to find a good mechanic shop and have them resurface the rotors with a on car lathe. I would almost bet that it would fix your issue. Good luck.

 

[airline tech]

There is another possibility, and it ties into what action was taken to swap the wheels , and that is the front end was raised off the ground.
This action pulls on the inner CV Joint via droop - this may have highlighted a wearing - CV Joint as it did not fully seat back into position when dropped back to the ground.

Just outside the box thinking.

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