Shimmy - Help, what could be wrong?

[dapakattack]

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!

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[RangerBill]

I would describe a shimmy as a slight side to side movement of the truck as it travels down the road. Is this what you are describing? The EGR sensor when bad, causes an engine power surging sensation (some say bucking) at part throttle.

Does one of the above describe what you are experiencing?

 

[dapakattack]

Yes, I would say more of a side to side movement....especially noticeable at highway speeds.

 

[RangerBill]

Yes, I would say more of a side to side movement....especially noticeable at highway speeds.

A bad tire (shifted belts) or a bent rim would cause a side to side shimmy.

 

[RangerBill]

Usually, a shimmy is more noticeable at slower speeds.

 

[Grish]

Have you checked the drive shaft and the carrier bearing? Heard those are troublesome.

 

[DukeCanBuildit]

You might want to have an alignment done...again. Maybe even a four wheel alignment - Phil had a good explanation on what happens when the rear wheels are not aligned. Maybe someone on here recalls that post and can point you to it.

Also, bent rear axle maybe? You wouldn't be the first.

 

[dapakattack]

Have you checked the drive shaft and the carrier bearing? Heard those are troublesome.

Thanks Michael. When I was under there checking other things out, I didn't notice anything out of the ordinary with the driveshaft. However, as long as its not dangling....I wouldn't know what to look out for.

You might want to have an alignment done...again. Maybe even a four wheel alignment - Phil had a good explanation on what happens when the rear wheels are not aligned. Maybe someone on here recalls that post and can point you to it.

Also, bent rear axle maybe? You wouldn't be the first.

Thanks Duke. Yes, I plan on doing a Thrust Angle Alignment at the dealership.

Appreciate everyone's input. Will get it figured out eventually.

 

[shovelhd]

Are you sure that the STX wheels were mounted completely flush to the hub, and were both clean (no rust or grit on the mating surfaces) when installed? If one or more wheels are even slightly cocked on the hub, you can have perfectly balanced wheels that will shimmy down the road.

 

[Motorpsychology]

You might want to have an alignment done...again. Maybe even a four wheel alignment - Phil had a good explanation on what happens when the rear wheels are not aligned. Maybe someone on here recalls that post and can point you to it.

Also, bent rear axle maybe? You wouldn't be the first.

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." ?

 

[Rp930]

Jack up each front wheel and spin the tire. Does it look like it’s running true?

Could also be a toe issue on alignment.

 

[carnut122]

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!

Did you get a 4-wheel allignment after doing all of the suspension work?

 

[dapakattack]

Did you get a 4-wheel allignment after doing all of the suspension work?

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.

 

[carnut122]

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.

How many miles do you have on the truck?

 

[got3fords]

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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