Freeway vibration is unnerving!
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Joined: Aug 2001
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From: Summerville, SC Near Historic Charleston
dcovell,
You must be an engineer who works for Ford.
How can you be so confident that the wheel base is what's causing the vibration unless you are an Engineer working for Ford!
BTW, the wheel base for the screw is not the same as the one for a Scab with the long box. The screw wheel base is the same as the Scab with the short box.
I've had a '00 Scab 4x4 with short box and never experienced the vibration mentioned here and now I own a '01 Screw and still no vibration and both have the same wheel base of 138.8 for the 4x4 and 138.5 for the 4x2. The Scab with the long box has a wheel base of 157.4 for the 4x4 and 157.1 for the 4x2.
I think you guess too much, get some info to back yourself up.
Jryager,
I think you are right on the rear quarter panels being something other than steel but I think they are a composite more like fiberglass but a member named logical knows this for sure. As for the hood, are you certain it's made of plastic 'cause mine sure looks like metal?
Everyone else,
As for the vibration, the most likely reason any car vibrates while driving is from the wheels being out of balance or out of round which cause the out of balance. The second most likely reason is from the driveshaft being out of balance. This is from experience and I'm not guessing.
IMO, the least likely reason is from the shocks since they are reducing vibration no matter what kind you have as long as they are in good condition. Some shocks work better at one vibration frequency and others work better at another one. Shock selection is not simple and no one can recommend one unless they know how a vehicle is going to be used and exactly what the payload is going to be and other factors.
Everything man made and natural has a vibration frequency that it doesn't like and it's called the natural frequency of the system. If a vibration in induced into a system that is close or near the natural frequency then the system will vibrate violently and will probably fall apart. I'm sure that's not the case here but I just wanted to say that and also to say that the Screw has a natural frequency too, one while it's at rest and a different one while in motion due to all the moving parts.
Vibration dampening is a classic engineering problem and the first thing to do is to find the frequency and magnitude of the vibration using instrumentation. Once the vibration frequency is known then the next order of business is to find out what is running at that speed, wheels, drive shaft, bearings, engine, transmission, belt driven accessory and the like. Once the rotating component is located that is causing the vibration then it's time to figure out why. Usually once the culprit is found it's pretty obvious why the vibration is happening but not always.
Another possibility is the aerodynamics of the screw, it too can cause a vibration and that also can be determined but a wind tunnel will probably be needed to prove that issue.
I know that almost no one has access to the kinds of testing equipment that is needed to test for the vibration and the dealer probably doesn't either but that's what is needed to solve this problem completely. So, get your wheels checked and look for missing weights on you driveshaft and after that then look deeper if you can't live with it and test it on a smooth road, not a rough one.
That's my $0.02
DaveMan
You must be an engineer who works for Ford.
Originally posted by dcovell
My truck virbrates around 60-70. At that higher speed I have never had problems.
It is due to the wheel base on the Super Crews and I eventually will be trying some diffrent shocks and maybe diffrent tires. Other than that I would say were stuck with this issue. I only have the problem in a few parts of the freeway where I live (San Diego) There are a few spot that are really bad but I don't drive on them that often at 60-70 MPH. Normally I'm going faster and theres no problem for me. I have a friend who has a f-150 extended cab with the long bed who has this exact same problem. That truck also has the same wheelbase as the SCREWs.
My truck virbrates around 60-70. At that higher speed I have never had problems.
It is due to the wheel base on the Super Crews and I eventually will be trying some diffrent shocks and maybe diffrent tires. Other than that I would say were stuck with this issue. I only have the problem in a few parts of the freeway where I live (San Diego) There are a few spot that are really bad but I don't drive on them that often at 60-70 MPH. Normally I'm going faster and theres no problem for me. I have a friend who has a f-150 extended cab with the long bed who has this exact same problem. That truck also has the same wheelbase as the SCREWs.
BTW, the wheel base for the screw is not the same as the one for a Scab with the long box. The screw wheel base is the same as the Scab with the short box.
I've had a '00 Scab 4x4 with short box and never experienced the vibration mentioned here and now I own a '01 Screw and still no vibration and both have the same wheel base of 138.8 for the 4x4 and 138.5 for the 4x2. The Scab with the long box has a wheel base of 157.4 for the 4x4 and 157.1 for the 4x2.
I think you guess too much, get some info to back yourself up.
Jryager,
I think you are right on the rear quarter panels being something other than steel but I think they are a composite more like fiberglass but a member named logical knows this for sure. As for the hood, are you certain it's made of plastic 'cause mine sure looks like metal?
Everyone else,
As for the vibration, the most likely reason any car vibrates while driving is from the wheels being out of balance or out of round which cause the out of balance. The second most likely reason is from the driveshaft being out of balance. This is from experience and I'm not guessing.
IMO, the least likely reason is from the shocks since they are reducing vibration no matter what kind you have as long as they are in good condition. Some shocks work better at one vibration frequency and others work better at another one. Shock selection is not simple and no one can recommend one unless they know how a vehicle is going to be used and exactly what the payload is going to be and other factors.
Everything man made and natural has a vibration frequency that it doesn't like and it's called the natural frequency of the system. If a vibration in induced into a system that is close or near the natural frequency then the system will vibrate violently and will probably fall apart. I'm sure that's not the case here but I just wanted to say that and also to say that the Screw has a natural frequency too, one while it's at rest and a different one while in motion due to all the moving parts.
Vibration dampening is a classic engineering problem and the first thing to do is to find the frequency and magnitude of the vibration using instrumentation. Once the vibration frequency is known then the next order of business is to find out what is running at that speed, wheels, drive shaft, bearings, engine, transmission, belt driven accessory and the like. Once the rotating component is located that is causing the vibration then it's time to figure out why. Usually once the culprit is found it's pretty obvious why the vibration is happening but not always.
Another possibility is the aerodynamics of the screw, it too can cause a vibration and that also can be determined but a wind tunnel will probably be needed to prove that issue.
I know that almost no one has access to the kinds of testing equipment that is needed to test for the vibration and the dealer probably doesn't either but that's what is needed to solve this problem completely. So, get your wheels checked and look for missing weights on you driveshaft and after that then look deeper if you can't live with it and test it on a smooth road, not a rough one.
That's my $0.02
DaveMan
Senior Member
Joined: Jul 2001
Posts: 513
Likes: 1
From: Raleigh, NC
Daveman,
Not sure about the hood, I recall seeing both plastic and aluminum. Plastic under, aluminum top... I'll take your word for it since I think your paint problems allowed you to see the metal (Sorry that happened)
I do remember reading something somewhere (I thought it was here but can't find it) that definitely said the rear quarterpanels were a plastic molded composite. Not fiberglass....
I'll keep looking.
Not sure about the hood, I recall seeing both plastic and aluminum. Plastic under, aluminum top... I'll take your word for it since I think your paint problems allowed you to see the metal (Sorry that happened)
I do remember reading something somewhere (I thought it was here but can't find it) that definitely said the rear quarterpanels were a plastic molded composite. Not fiberglass....
I'll keep looking.
Senior Member
Joined: Aug 2001
Posts: 1,609
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From: Summerville, SC Near Historic Charleston
Hey Jr,
I checked the hood of my '01 screw, it's not magnetic but it must be metal on top 'cause I can see where it wraps around and folds under on the edges, can't do that with plastic very well. I'm going to guess aluminum too as it would be strong enough and a good chioce IMO. The bed sides are also non magnetic, as has been mentioned, but the tail gate is magnetic. All the fender and door panels are magnetic as well as the front apron near the radiator.
Where's logical when you need him 'cause this is what he does for a living, for the Ford Screws no less, and he could clear it all up in a second.
Anything magnetic I'm assuming is steel, I assuming the hood is aluminum on both sides and the bed outer skin is made of a composite plastic similar to fiberglass.
For those who think or agree that one reason the Screw vibrates is from it being too light in the rear, look at the specs on the enclosed pdf file on page 28 and compare rear axle weight to front axle weight ratios and then comment on the screws.
http://www.fleet.ford.com/truckbbas/...001/f150cd.pdf
According to Ford, the 4x4 screw has a ratio, front to back of 0.719 (2124/2953) or 28.1% less weight in the back than in the front. On a short box regular cab 4x4 it's 0.717 (1888/2633) or 28.3% less in the rear than the front. Using the same 138.8 wheel base, that sounds close enough to call it the same from two totally different chassis with different wheel bases and the screw with it's composite bed panels. I'd say Ford did their homework!
Now lets look at a long box Super cab 4x4. It's 0.688 (1987/2886) or 31.1% less in the rear than the front, what a surprise for a long bed with a steel box! All the ratios are unloaded so each one of us will probably have different numbers but it's just for comparison sake.
Now with all that said, does that help solve the vibration issue of this thread, probably not but it ought to wake up some speculators!
DaveMan
I checked the hood of my '01 screw, it's not magnetic but it must be metal on top 'cause I can see where it wraps around and folds under on the edges, can't do that with plastic very well. I'm going to guess aluminum too as it would be strong enough and a good chioce IMO. The bed sides are also non magnetic, as has been mentioned, but the tail gate is magnetic. All the fender and door panels are magnetic as well as the front apron near the radiator.
Where's logical when you need him 'cause this is what he does for a living, for the Ford Screws no less, and he could clear it all up in a second.
Anything magnetic I'm assuming is steel, I assuming the hood is aluminum on both sides and the bed outer skin is made of a composite plastic similar to fiberglass.
For those who think or agree that one reason the Screw vibrates is from it being too light in the rear, look at the specs on the enclosed pdf file on page 28 and compare rear axle weight to front axle weight ratios and then comment on the screws.
http://www.fleet.ford.com/truckbbas/...001/f150cd.pdf
According to Ford, the 4x4 screw has a ratio, front to back of 0.719 (2124/2953) or 28.1% less weight in the back than in the front. On a short box regular cab 4x4 it's 0.717 (1888/2633) or 28.3% less in the rear than the front. Using the same 138.8 wheel base, that sounds close enough to call it the same from two totally different chassis with different wheel bases and the screw with it's composite bed panels. I'd say Ford did their homework!
Now lets look at a long box Super cab 4x4. It's 0.688 (1987/2886) or 31.1% less in the rear than the front, what a surprise for a long bed with a steel box! All the ratios are unloaded so each one of us will probably have different numbers but it's just for comparison sake.
Now with all that said, does that help solve the vibration issue of this thread, probably not but it ought to wake up some speculators!
DaveMan
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Joined: Jul 2001
Posts: 681
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From: Motor City Suburbs
The hood is in fact alluminum. Let me clear up the composite vs. plastic vs. fiberglass deal. The rear quarter outers (or fenders...or bodysides) are a "composite" material which just means it is a material made up of several materials. The floor and inside walls of the box are steel.
This particular "composite" happens to be about one third fiberglass (strands maybe one inch long). It is also about one third thermoset (which just basically means that you can't melt and reshape it) polyester resin (plastic). The other third is actually crushed calcium carbinate (limestone). It is formed in a mold at about 300 deg. F in a press that creates maybe 1500 tons (yes, tons) of force. Bored yet?
This same basic recipe is what many of the Corvette panels have been for years and still are.
Some call it plastic and I suppose they are partially right....some call it fiberglass and they are no less correct. Lots of people talk about a boat being fiberglass but they too are composites...just different recipes. I suppose you are just as correct to call it rock, but nobody does. But fiberglass alone won't make a class "A" body panel, or a boat for that matter. And plastic alone won't be strong enough to hold its shape. And limestone is..errr...well it's cheap.
So...it is a "compression-molded, mineral filled, fiberglass-reinforced, thermoset polyester composite material"
Oh yeah...they aren't that much (if any) lighter than steel fenders in this kind of application. Lower density thal steel but thicker.
This particular "composite" happens to be about one third fiberglass (strands maybe one inch long). It is also about one third thermoset (which just basically means that you can't melt and reshape it) polyester resin (plastic). The other third is actually crushed calcium carbinate (limestone). It is formed in a mold at about 300 deg. F in a press that creates maybe 1500 tons (yes, tons) of force. Bored yet?
This same basic recipe is what many of the Corvette panels have been for years and still are.
Some call it plastic and I suppose they are partially right....some call it fiberglass and they are no less correct. Lots of people talk about a boat being fiberglass but they too are composites...just different recipes. I suppose you are just as correct to call it rock, but nobody does. But fiberglass alone won't make a class "A" body panel, or a boat for that matter. And plastic alone won't be strong enough to hold its shape. And limestone is..errr...well it's cheap.
So...it is a "compression-molded, mineral filled, fiberglass-reinforced, thermoset polyester composite material"
Oh yeah...they aren't that much (if any) lighter than steel fenders in this kind of application. Lower density thal steel but thicker.
Last edited by logical; Dec 2, 2001 at 11:24 PM.
Senior Member
Joined: Jul 2000
Posts: 5,116
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From: Houston, by way of every major city in America.
If you guys think that is bad, you ought to try any freeway in Detroit. I'm talking road damage that bounces you into the next lane I was surprised my shocks survived that four weeks of hell!,,,,98
I was surprised my shocks survived that four weeks of hell!,,,,98
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Joined: Jul 2001
Posts: 1,247
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From: El Cajon, CA
NOPE not an engineer, for anyone. I work on computers for a living and yes I am making assumptions. But from what I have seen it has a lot to do with it. My SCREW and a friends f-150 with the same wheelbase (diffrent shocks, ones 4xs2 and mines 4x4, diffrent tires) we both get the freeway vibration in the same areas.
Not gona say I'm right or wrong, just posting my opinions.
Not gona say I'm right or wrong, just posting my opinions.
Member
Joined: Apr 2001
Posts: 94
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From: Southern California
I just expected my truck to be made of metal, to find out that part of it is plastic it was dishearting. I think it was just a mental thing, kinda like when I found out my old dodge 2500 was made in Mexico.
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Joined: Aug 2001
Posts: 378
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From: Houston, Texas
Originally posted by xdodgeguy
Here is a picture of the bed on my Screw after being hit. Just for the non believer that thinks it metal. I was bummed to find this out.
Here is a picture of the bed on my Screw after being hit. Just for the non believer that thinks it metal. I was bummed to find this out.
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Joined: Jul 2001
Posts: 681
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From: Motor City Suburbs
xdodgeguy-
Your picture shows the fiberglass reinforcement that I talked about in my earlier "lecture".
You are disappointed that the same technology used on Corvettes, the new T-bird, the current Camaro/Firebird, the Lincoln Continental, the Mustang...and dozens more was applied to your truck???????????? grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr....would it make you feel better if Ford had the supplier mix in some metal shavings so you could see it rust a few years down the road like steel could?
jryager-
The Bronco II liftgate, at least some if not all of them were composite...some cracking problems with them if I remember correctly (no personal involvement).
The original Windstar Hood up to '98 was composite, but I can't remember about the liftgate.
Your picture shows the fiberglass reinforcement that I talked about in my earlier "lecture".
You are disappointed that the same technology used on Corvettes, the new T-bird, the current Camaro/Firebird, the Lincoln Continental, the Mustang...and dozens more was applied to your truck???????????? grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr....would it make you feel better if Ford had the supplier mix in some metal shavings so you could see it rust a few years down the road like steel could?
jryager-
The Bronco II liftgate, at least some if not all of them were composite...some cracking problems with them if I remember correctly (no personal involvement).
The original Windstar Hood up to '98 was composite, but I can't remember about the liftgate.
Last edited by logical; Dec 5, 2001 at 03:53 PM.
Senior Member
Joined: Jul 2001
Posts: 1,247
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From: El Cajon, CA
Well I guess it all depends on how much it will cost to fix it. Is it cheaper to fix the composite vs the sheet metal? I don't care that much about the side not being metal, at least I don't have to worry about kids sticking magnets to the side of the bed...
Member
Joined: Sep 2001
Posts: 25
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From: Simi Valley, CA
Ok all- I've posted before about the vibration and I finally got the dealer to admit there is a problem. Of course this is after I dropped it off and said Im not picking it up until the vibration is gone... So a week later they tell me they can duplicate the problem and they put on a damper. The writer cant explain what a damper is or where it goes, just that the mechanic put one on and they want me to drive it. So Im going down there now to drive it- I'll let you all know what the effect is later today.
My question is has anyone else had a damper installed? Does anyone know pros or cons to this solution? My feeling is a damper just masks the problem but doesnt really fix anything and I'm worried that the vibrations, although masked, will cause wear issues down the road- like right after the warranty is up- then I'm on the hook for the parts. I'm no mechanical engineer, just thinking (worrying??) out loud...
Any thoughts from the gallery??
Thanks for your ideas!
Judd
My question is has anyone else had a damper installed? Does anyone know pros or cons to this solution? My feeling is a damper just masks the problem but doesnt really fix anything and I'm worried that the vibrations, although masked, will cause wear issues down the road- like right after the warranty is up- then I'm on the hook for the parts. I'm no mechanical engineer, just thinking (worrying??) out loud...
Any thoughts from the gallery??
Thanks for your ideas!
Judd
