Hood Sheet Metal Thickness

AirBender · Jul 21, 2015

Huh....

jarvo said:
My truck hood flutters on the highway on the drivers side.I took it to the dealer and they told me there was a service bulletin on the hood,so they order the spray.After a month they received the spray and did the hood and tried to adjust it but it still flutters on the highway but only in the front drivers side.Go see the dealer for help.

As I mentioned earlier, I too have this minor issue on the drivers side. But I'm sorry....a "spray" to adjust the hood? I must not be understanding you. :?
The service bulletin you mentioned just describes adjusting the hood riser and latches. What is this "spray" you speak of?

CaryBosse · Jul 21, 2015

AirBender said:
As I mentioned earlier, I too have this minor issue on the drivers side. But I'm sorry....a "spray" to adjust the hood? I must not be understanding you. :?
The service bulletin you mentioned just describes adjusting the hood riser and latches. What is this "spray" you speak of?

They spray or more typically, it is called "blow" a foaming agent into the hood that created a foam sandwich, adhering to the two pieces of aluminum of the hood and making it more rigid to reduce flexing.

AirBender · Jul 21, 2015

CaryBosse said:
They spray or more typically, it is called "blow" a foaming agent into the hood that created a foam sandwich, adhering to the two pieces of aluminum of the hood and making it more rigid to reduce flexing.

Oh wow...interesting. Thanks for the info CB. hmmm...I'll pass on that though. I think a fairly simple adjustment for mine will suffice.

white cat · Jul 21, 2015

My brother and I both bought new Canyon SLE's neither one of them has hood flutter, or has hood flex, with out pressing real hard. This is really weird that some have it and others do not.

CaryBosse · Jul 21, 2015

AirBender said:
Oh wow...interesting. Thanks for the info CB. hmmm...I'll pass on that though. I think a fairly simple adjustment for mine will suffice.

white cat said:
My brother and I both bought new Canyon SLE's neither one of them has hood flutter, or has hood flex, with out pressing real hard. This is really weird that some have it and others do not.

I think the flutter that is attributed to bumpers needing adjustment is easy to see how it could vary from truck to truck. The flutter that I think I am seeing that I think can be fixed by the foam should not be as variable from truck to truck. I don't see an adjustment at the rear that could "tighten" this up. Also, my hood is already pretty tight - you have to really drop it to get the latch to properly close.

GeneP · Jul 21, 2015

CaryBosse said:
I think the flutter that is attributed to bumpers needing adjustment is easy to see how it could vary from truck to truck. The flutter that I think I am seeing that I think can be fixed by the foam should not be as variable from truck to truck. I don't see an adjustment at the rear that could "tighten" this up. Also, my hood is already pretty tight - you have to really drop it to get the latch to properly close.

The "Flutter" that I see on my hood is the same area of the hood I took the video of. The sheet metal in the same area actually buckles up & down at +60 MPH speeds.

Not sure about the foam repair. I read in another post that the attempt to correct with foam just bulged the hood in that area from too much foam.

Gene

CaryBosse · Jul 21, 2015

GeneP said:
The "Flutter" that I see on my hood is the same area of the hood I took the video of. The sheet metal in the same area actually buckles up & down at +60 MPH speeds.

Not sure about the foam repair. I read in another post that the attempt to correct with foam just bulged the hood in that area from too much foam.

Gene

Let the service department do the foam, if they warp your hood, they replace it.

I can see where it might be possible with a foam that expands at a high rate might warp the hood. However, if the foam correctly adheres to the top and bottom "skins" of the hood, it will create a much stronger structural part without adding significant weight.

I wonder if the foam is fire retardant. I doubt it, but if so, it might have helped a tiny bit on the guy with the truck fire who posted earlier today.

LordXayd · Jul 21, 2015

Hi Cary, when I said pour, I was referring to when they pour molten aluminum into sheet mold.

Also, my 2008 Dodge Caliber's hood would not flex if a fat cat walked across it. It would flex if he leapt from it, but not in any fashion that would concern me. But you said that the exterior bed sheeting is flexingalso ? I think I'm going to have to test this myself in comparison to a Sierra. Part of the reason I'm waiting on the diesel is because I really want to try for a 20 year vehicle. A truck frame will last for 20 years, but a gas engine won't (unless you're a good mechanic and go easy on the truck). So I figured it was a good marriage, a truck with this Duramax.

But man, if the truck itself is compromised right on the factory floor, maybe I will go with that Sierra instead. I'll just have to see.

CaryBosse · Jul 21, 2015

LordXayd said:
Hi Cary, when I said pour, I was referring to when they pour molten aluminum into sheet mold.

Also, my 2008 Dodge Caliber's hood would not flex if a fat cat walked across it. It would flex if he leapt from it, but not in any fashion that would concern me. But you said that the exterior bed sheeting is flexingalso ? I think I'm going to have to test this myself in comparison to a Sierra. Part of the reason I'm waiting on the diesel is because I really want to try for a 20 year vehicle. A truck frame will last for 20 years, but a gas engine won't (unless you're a good mechanic and go easy on the truck). So I figured it was a good marriage, a truck with this Duramax.

But man, if the truck itself is compromised right on the factory floor, maybe I will go with that Sierra instead. I'll just have to see.

These are not die cast hoods, these are stamped hoods. Same process as a steel hood, with adjustments for the tensile and malleability of the aluminum versus steel, of course.

Just to make sure we are on the same page, I am talking about leaning against the fender to place a 40 pound piece of flagstone gently on the bed floor, I felt the fender flex as I leaned pretty heavily on it, but it popped right back out. Not sure if your "exterior bed sheeting" is the same thing I am describing. I do know my C1500 Sportside with fiberglass fenders never had any issues with flex on the fenders.

In that regard, you might want to read about the fuel cover issues some have had. These trucks are not built like a 1960s truck with sheet metal that anyone with a welding machine and a coat hanger could weld up a hole with. I don't think you will find much difference with a FS truck, you might also want to consider getting a FS truck before GM goes down the aluminum rabbit hole - all the "experts" who blow smoke on the internet claim GM and Ram are not far behind Ford in converting to aluminum.

I think the frame is still good - no one has suggested they have degraded the frames to that degree. Only Honda has stayed away from the body on frame design and gone to unibody construction.

gstaylorg · Jul 21, 2015

Anyone reading this thread that thinks this is "normal" for aluminum, just go back and look at the video again. It's almost as if the thickness of the stamped hood is not uniform. There is no way it should be deformed like that with just a slight push of a finger. I went back and checked mine last night after reading this and sure enough, there are places where it can be depressed much more easily than others. It was not nearly as easily deformed as the OPs, but way easier than it should be. This whole hood issue is bullshit and don't think GM doesn't know about it. Clearly, the thickness of the sheet is not uniform. It is not an issue of the support underneath, because the same spots on opposite sides of the hood don't do it, regardless of the fact that what's underneath is the same. Metal that is that weak will be deformed when the foam [so-called] fix is applied underneath and it hardens. This is what happened to mine, leaving a nice bulge across one of the hood ridges. Now I understand why. Sure, I could have them replace it. Maybe I'd get a good one, maybe another POS. Either way, the replacements hoods come from the factory unpainted, and have to be painted at the dealer. Even the body shop manager at my local dealer told me that no way would their paint job be the same as factory. Of course the color would match, but that's not all there is to a good paint job. It's a real shame that something as simple as a stamped piece of aluminum could detract so much from what is otherwise (IMO) an unbelievable design.

rjanuary · Jul 21, 2015

gstaylorg said:
...It's almost as if the thickness of the stamped hood is not uniform....Clearly, the thickness of the sheet is not uniform.

It's not nearly that easy. I would say with an extreme level of confidence that the thickness is extremely uniform since it is stamped. There will be slight localized differences, but not enough to make this profound of a change.
You need to look at the shape of the panel as a whole. The more curves/ridges you have in a panel (or a portion of a panel in this case) the stiffer it will be.

Try to push in the nose of the hood. It's extremely stiff due to the compound curves. The area around where OP is pushing on his hood is flat as a pancake, which is why you're seeing more flex there.

gstaylorg · Jul 21, 2015

Did you read what OP and I both wrote? Pushing on comparable spots (equidistant R/L of center for example) in areas where the the shape and underneath support are exactly the same don't yield the same result in terms of flex.

LordXayd · Jul 22, 2015

CaryBosse said:
These are not die cast hoods, these are stamped hoods. Same process as a steel hood, with adjustments for the tensile and malleability of the aluminum versus steel, of course.

Right, but I'm not talking about GM's end. I'm talking about before then, whatever contractor is smelting the aluminum ore and forging or pouring it molten into sheets (for later stamping). That guy. I dont think his process is uniform.

rjanuary · Jul 22, 2015

gstaylorg said:
Did you read what OP and I both wrote?

I did. Have you ever worked sheetmetal in a body shop? I speak from experience. I'm not saying it's not an issue. I'm saying that thickness has nothing to do with it.

EDIT:
This begs the question of "If not thickness, what's the issue" Without seeing the panel in person it's difficult to say definitively. If I were forced to make a determination it would be my guess that it has to do with the way the inner structure was skinned. For lack of a better term, the skin wasn't "stretched" enough when applied to the inner structure.
Best case scenario for this hood is exactly what was already stated. Expandable foam which will cary the load to the framework.

iTom · Jul 22, 2015

I don't know what the panic is other than some folks being distracted by it while driving. Aluminum flexes. So what. It's also extremely strong. Sheets are run thru roller presses and are not going to vary in thickness over .002-.003 if that much. Like a steel hood of recent times this aluminum hood is going to dent from hail,a golf ball or football as shown in the pictures. But it's also going to be much more resistant to creasing like a steel hood would from something like someone sitting on it. Aluminum just doesn't crease the same as steel. I'm not questioning the video at all. But I also wouldn't trust trying the expansion foam personally. Let the "experts" do it so they can be responsible when it bulges. So it flexes? As Cary Bosse pointed out it pops right back in place and that's what matters. We all want great mileage but we also want the metal to be like the tanks of yesteryear. It ain't happenin'. We work ourselves into a frenzy over this stuff from the mob mentality that this ain't right. Perhaps it's just because it's not what we're used to. With that being said it will be interesting to see how this turns out on the 2016's.

CaryBosse · Jul 22, 2015

I don't know where to begin.

Sheet metal used to make these hoods is not "poured" as it is made into a sheet, and it runs through a mill to bring it down to the desired thickness. iTom mentioned a .002 to .003 variation, but did not say what unit of measure. I am an old English (inches) guy, this metric stuff always confuses me. I would argue that you are probably looking at variations more in like 0.0002-0.0003 INCHES in the thickness of the metal these hoods are made from. Anything more than that and the press that stamps out the hood could never hold tolerance for the finished hoods.

I believe if there is truly a variation in the flex of the hood at different points, it is because the temper of the aluminum is not consistent. This could be caused by variations in the ovens where the aluminum is tempered, but my guess is that if there are variations, it is caused by work hardening of the aluminum: as you work aluminum, it will cause it to become harder and more brittle. My memory, that is failing at my old age, is that aluminum is much more susceptible to work hardening than steel.

In steel, you will hear people talk of cold rolled or hot rolled steel. The difference is that the steel is rolled between the rolls that define the final thickness cold, thus inducing more work hardening into the steel, or hot rolled, to reduce the amount of work hardening induced into the steel. Similar results with aluminum, though I don't have as much knowledge of that area. (I have never been involved in the actual manufacture of metals, I just had to order them, including steel, stainless steel, aluminum, brass.)

The process of forming a hood induces work hardening into the material. Anywhere the material is formed it will be work hardened.

I am not expressing an opinion of the acceptability of the flex on these hoods, but for what I have seen on my hood, the flexibility is probably not out of line with other hoods. I would be looking at the foam as just an added little structural support. It will also minimize how much you can use your fingers to flex your hood.

08Canyon · Jul 22, 2015

I think you guys figured out GM's Easter Egg built into the truck.

The hood is nothing but an science experiment and a metallurgy 101 crash course.

Suns_PSD · Jul 22, 2015

Peterbilt 379 hoods flex and vibrate significantly (like 1/2") the entire time you drive them for millions of miles with no damage what-so-ever. And they aren't damaged by fat cats jumping on them either.

This whole topic is a non-issue.

GeneP · Jul 23, 2015

Suns_PSD said:
Peterbilt 379 hoods flex and vibrate significantly (like 1/2") the entire time you drive them for millions of miles with no damage what-so-ever. And they aren't damaged by fat cats jumping on them either.

This whole topic is a non-issue.

Apparently GM thinks its an issue. I found a link with among other issues it address for this vehicle it addresses the hood. Some really good info I found here. Go to the very bottom of the page. It has instructions for injecting Kent® Ure-Foam Expandable Foam Sound Deadener into the hood. (Refer to #PIT5340)

Heres the link: Search Results colorado

Gene

LordXayd · Jul 24, 2015

I was at the GMC dealer today. I tested the hoods of a Canyon and Sierra. They were both fine. Little bit of flexing, but nothing to be concerned. The rest of the body is made out of steel, but I tested it anyway. The only paneling that bubbled noticeably was the doors, but still nothing to be concerned about.

I think Gene has a bum hood that needs to be replaced.

Hood Sheet Metal Thickness

AirBender

CaryBosse

AirBender

white cat

CaryBosse

GeneP

CaryBosse

LordXayd

CaryBosse

gstaylorg

rjanuary

gstaylorg

LordXayd

rjanuary

iTom

CaryBosse

08Canyon

Suns_PSD

GeneP

LordXayd

Top Contributors this Month

Recommended Communities