I took my 55 F350 to a local tire shop today to have the front wheels balanced. The truck starts to shimmy at around 45 mph. Sometimes if I can speed up quickly past 45 mph and get up to 50 to 55mph I can avoid the shimmy. The guy said my wheel bearings might need replaced as checked them with the wheels off the ground and that might be the cause of the shimmy. The one wheel needed 1.25 and the other needed .75. They charged me only $16.

On the way home it still shimmied when I got it up to speed.

So would worn wheel bearings cause a truck to shimmy?

 

Yes, a loose or worn wheel bearing can cause a vibration. If they balanced the wheels on the truck, I would have expected the tech to adjust the wheel bearings if he determined them to be loose. Just because a wheel bearing is loose does not mean it is worn out. Have you ever cleaned and packed the bearings on the front of that F350, Abe?

 

I would repack the wheel bearings and properly set the locking nut.
A bad wheel bearing typically howls and gets quiet on corners as you load it up.

Kirk

 

No, I have not.

 

Abe,
you should!
good luck.
Greg

 

Yes, I will. I just have to decide wether to do it now or in the spring. It is going into storage next week.

 

Glad I found this thread. I seem to have a shimmy at around 60 but not at 65. I think it might at some other speeds as well. I need to see if I can find patterns.
Well really, I just need to check my wheel bearings.

 

And of course, you and BJ made certain the axle bearings are getting lubricated in the new rear end? Lubrication is at the correct level, right? And, if your fronts have not been checked since you've taken possession of the truck, time to do so.

 

The wheel bearings are definitely a great place to start, but if that doesn't solve it, it wouldn't hurt to check your tie rod end condition also and get the alignment checked as well if you haven't already. These trucks can't tolerate any appreciable wear at all in the tie rod ends if they are used on modern roads. With the way the steering linkage is set up, any wear or looseness at all in the tie rod ends stacks up to affect only the right wheel and can manifest as a shimmy. As far as the alignment goes, you should have about 1/16" toe-in and somewhere between 2 and 4 degrees of caster with manual steering. Any amount of positive caster up to about 7 degrees is actually OK and will help the wheels return to center and make the truck feel more stable in general at speed, but over 3-4 degrees can make it a real handful to steer at low speeds without power assist. It's hiding somewhere in the bearings, steering linkage, or alignment. A little poking around under the front end ought to turn it up!

 

Thanks guys for all the advice!

And Joe, now with the new rear end and gears you are going faster so you are finding more problems! But you'll fix em.

 

BJ filled the axle. It makes sense to check it after driving a few miles to make sure the oil has made it to the bearings.

Good info. I replaced the tie rod and ends about 1500 miles ago. At that time, I took it in to get aligned. They couldn't do much with camber and caster. I have caster of 5.1 and 7.0 and camber of -0.6 and -0.3. For the caster, I have shims with the big end toward the back. If I remove those will it bring my caster closer to where it needs to be? I think that is what I read, but I'm not confident. I think they are 2 degree shims. As I'm watching youtube to learn, caster won't impact shimmy especially at my number, correct? Time to go crawl under the front...and back to check fluid levels....and see what I can see.

 

Don't mistake wheel hop or bounce due to bad shocks or an out of round tire with shimmy. I know Abe's question was about wheel bearings but this all is about drivability and safety.

 

Good point, I know mine is definitely a shimmy. When BJ picks his truck up from the body shop, he will stop by my place to install glass. If the weather is ok, I will throw him in the truck and we can discuss what we are feeling.
I plan to check the bearings before that though...I hope...off to Olive Garden to take my daughter out for birthday lunch, so not today. The closest Olive Garden if 45 minutes away.

 

Your camber numbers are fine for a straight axle truck - which is good because the only way you can correct them is to literally bend the axle. Your caster is a bit surprising, though. Up to a point, more is better when it comes to caster. The unfortunate side effect is that the more positive caster you have, the farther the wheels have to lift the front of the truck when you steer away from center and low speed steering effort goes up considerably. If you can deal with the way it steers at low speed right now, I certainly wouldn't remove the wedges just to get closer to 3 or 4 degrees. What concerns me the most is the 2 degree difference from side to side. Caster should be exactly the same on both sides and 2 degrees is a huge difference. Your caster numbers in and of themselves shouldn't cause a shimmy, but the difference potentially can! It can also cause a pull to one side and other general funkiness in the handling. There is apparently a bit of twist in one end of your axle if you have these numbers with the same size wedges on both sides. You can probably correct this by changing the wedge on the 7 degree side and attempting to match it to the 5 degree side. Pull the wedge and determine exactly how many degrees it adds. It should be marked, but a few quick measurements and a little geometry can determine its angle if it isn't. If it is in fact a 2 degree wedge, then leave it out on that side and have your alignment rechecked. If it's a 4 degree, try replacing it with a 2 degree, etc.

If correcting your caster difference doesn't eliminate your shimmy, then you might take another look at your toe setting. Larger truck tires have more leverage and can generate more force pushing the front of the wheels apart as they roll down the road. If you don't have enough toe-in, you can actually end up with a toe-out condition as the wheels push apart at speed and that can cause all kinds of squirreliness - including a shimmy. 1/16" to an 1/8" of toe-in is the standard toe setting, but with a larger truck like yours, you can sometimes get away with 3/16". Keep an eye on your tires for the first few hundred miles if you try this. Too much toe-in can cause them to scrub and wear funny on the outside edge.

Last thing - chasing stuff like this is when it's really handy to have an inexpensive caster/camber gauge. There are a few different types available. eBay is a good place to find them if you're interested. Fancy 4-wheel laser alignment equipment is necessary for modern cars, but you can do a really good alignment on an older vehicle in your garage with just a caster/camber gauge, a tape measure, and some patience!

 

Fantastic info! I will look at this more closely after I get the tie rod end straightened out.
Now I'm wondering if the shims were different and if I just put them back in wrong when I cleaned everything up the first time.