Why no replies??

With all due respect back to you, Tim, your original post didn't give anything to go on, and I for one still don't understand your first sentence.

What shimmy? When does it occur? Is it in the front? Is it in the rear? Is it in the steering wheel? is it in the seat? Does it do it at a certain speed? Does it do it when you hit the brakes? Does it do it when you hit bumps?

You've got to give details, then maybe someone will have some answers, and caution, there will be a few who answer you whether they know or not.

Spdloader

It could simply be that nobody knows the answer. Maybe some more details.

In your original post: You titled 2002 F53 Chassis, but the first sentence says 2003. You have a Ford F53 Chassis You have a Ford F52 Chassis It shakes, but not enough to cause concern. It almost shook the unit apart. You had to slow down to 10MPH to stop the violent shimmy. Which is it?

No description of the "shake" or "shimmy" itself. Is it in the front? rear? both? Side to side? up and down? Can it be felt in the steering or brakes?

It's like saying - "My truck makes this noise. What's the fix?"

When did it start? I think that's a key question. Has it been like this since you bought it? Did you buy it used? If you've had it for a while and it started more recently, when did it change? Was it a gradual change? Did it occur after you hit a pothole, heard a pop, strained the suspension, changed tires, or anything similar? Does it make any noises that it didn't used to make?

CJB

Tim, I can think of only two things right off, and they may not be at fault, but, in the driveline you have carrier bearings that support a looooooong driveshaft. My dumptruck acts the same way as you describe when the carrier bearing needs to be replaced. It once shook the A/C condenser box loose from the firewall doing it. The other thing is maybe you have a bad u joint.

TransSurgeon is the best trans guy in this newsgroup, maybe he'll have an idea, or at least a mathematical formula explaining why yours does what it does.

(lol jk TransSurgeon) Good luck,

Spdloader

It sounds like you are getting help from the RV group, but just don't want to take it. You might have to take matters into your own hands and get it fixed outside of warranty.

I used to have a Ford van that did the exact same thing, and it turned out the idler arm bushings were worn. That that was back in '72 and I don't even know if trucks have idler arms anymore. But if they do, it'd be something to check out.

CJB, Thanks for your reply.. It always rode great on smooth roads and it felt like a city bus when going over the concrete expansion joints etc. It shimmied just a little but I thought it was normal for a big vehicle. Yes, it drove this way from the beginning. It's only or second summer using it. WE bought it new in 2003 but I was laid up and didn't use it until the next summer. We've got about 22 thousand miles on it. (it's in kilometers so that's not an exact conversion) No, the violent shimmy ie shaking happened when bumps were a certain frequency. I didn't really see the bumps. Route 4 in Nova Scotia. I had it aligned a wheels balanced and rotated last season. and had it checked out by the Ford dealer before the trip this season. Hope this helps. Tim fm Ct

Would this happen in only 20+ thousand miles???

Hi Al, No that's not quite the way it is. Fact is some one mentioned a service bulletin but due to computer and operator error. I lost it. The rv newsgroup is great but it wasn't 2002 Ford f53 specific. Seems to me, if it takes a third party product to solve a shimmy problem. I'd rather hear from Ford owners first' Some of the RV group replies dealt with other brands of RV's and I don't know if they were 2002 f53 chassis. You might be right though... it may take a third party product to fix it. I hope not. I hope Ford steps up and fixed it. Tim fm Ct

Thanks Frank, Don't forget though the whole front end was checked before our trip. Also, I've heard more stories about the roads of Nova Scotia, but the bumps weren't big visible bumps. After the incident, I could see them just as the sun was setting and the light cut across the highway. Thanks again

So the answer is that it's always had this problem but it's getting worse and worse. That's not good. Have you talked to anyone else who has the exact same coach and chassis as you? I'm going to go out on a limb and say that it might well be a harmonic, aka oscillation, problem. Everything in the world vibrates at a particular intrinsic frequency depending on its mass and dimension, among other things. Bigger things tend to oscillate at lower frequencies. I'd imagine that the long solid walls, ceiling or floor of a motor home would have a pretty low natural resonant frequency. And because of their size, they'd probably really vibrate badly if you happened to set them in motion.

If you remember anything about the Tacoma Narrows Bridge disaster, you may remember that as a classic example of an oscillation problem.

Now, the problem MAY be that you have something in the suspension or drivetrain that oscillates at a frequency to which the coach is resonant. If you can find the source of the initial oscillation, then you can probably stop the coach from oscillating. Someone suggested that it may be a carrier bearing. That's possible. It could be about anything in the drivetrain. It could be a bad shock absorber that allows the suspension to pitch at just the right frequency, etc.

In cars, sometimes a vibration will occur that feels like a tire out of balance but is actually a part of the drivetrain that is out of balance. They require a dynamic balance in which the wheel is spun while still attached to the car so the entirety of the running gear is tested for balance. If such a thing were available for something as big as your motor home, I'd be interested in trying it.

I hope for your sake I'm dead wrong; I think I'm right about a running gear problem starting an oscillation of either the chassis or (more likely) the coach. If you can contact someone with extensive knowledge of your exact setup, I think you may be more apt to find the fix.

CJB

Brand new parts can be bad right from the start. Or, improperly installed.

So, Yes, it can happen in only 20+thousand miles, or less.

Spdloader

I had two trucks long, long ago that did the same thing. One was a 1960 International Scout. The other was a 1974 Ford 4x4. It was the front wheels that shimmied. It would start if I hit a bump just right. The only way to stop it was to slow down to a crawl. The steering wheel was nearly impossible to hang on to. What cured it was some sort of shock absorber that one of the suspension places here put on.

I would certainly think they could with enough time. I also think that the RV manufacturer should be able to help you even quicker. Surely you're not the first to express such a problem. People with specialized knowledge of something are usually quicker to diagnose and fix that thing. An RV is a special application.

Frankly, that's why I'm worried. I think the problem may lie in the actual mating of that chassis to that coach. Perhaps they just don't work well together. When you said that the problem has been there to some extent all along, that was a red flag to me. What I think is going to happen is that the coachbuilder is going to tell you that it's a problem with the chassis, and the chassis builder (Ford) is going to tell you that the chassis is working precicely as it was designed. It's entirely possible that the coach is simply ill-designed to work with that chassis.

Maybe I'm wrong...

CJB