Noisy Demon trunk lid?

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French demon

French demon

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Hi all,

For a long time now, I hear a loud noise in the trunk while driving, especially on bumpy roads. Like if an heavy thing was bouncing into the trunk.
It is very unpleasant
Despite my searches, I didn't find where this noise comes from.
It's not the spare tire, jack or tools, not the exhaust, not the gas tank, not the rear seat, not the package tray...

I suspect my trunk lid. I have the early flat model, the one without a rib in the middle.
Rear.jpg

The lid is in an excellent shape, but is it possible that the inner liner hits the outer steel sheet causing this noise..?

I will try driving with the lid removed, but wanted to know what you think about that?

Cheers... :)
François
 
Check the rubber bushings on your leaf springs, shackles and shock absorbers.
While you're checking the shocks, make sure the pins are still tight- I have seen them work loose from the shock crossmember and/or from the shock plates.
 
Did you know the spare tire holds the gas tank up . Anyway check the trunk hinge springs your rubber insulator is probably off and they are hitting.
 
Oldmanmopar said:
Did you know the spare tire holds the gas tank up . Anyway check the trunk hinge springs your rubber insulator is probably off and they are hitting.
Click to expand...
You mean the torsion spring? Yes they have "rubber hose " that goes over them... :thumbsup:
 
Professor Fate said:
Check the rubber bushings on your leaf springs, shackles and shock absorbers.
While you're checking the shocks, make sure the pins are still tight- I have seen them work loose from the shock crossmember and/or from the shock plates.
Click to expand...

I forgot to write that the shock absorbers are brand new.
I will have a look at the leaf springs bushings, but the noise seems to come from the trunk, not from under the car.

Oldmanmopar said:
Did you know the spare tire holds the gas tank up . Anyway check the trunk hinge springs your rubber insulator is probably off and they are hitting.
Click to expand...

Do you have a picture of these hinge spring rubber insulators? I don't know what you are talking about...

:thankyou:
 
Also, check inside the trunk along the sides where the dropoffs leave a gap between them and the quarter panel- errant tools and other objects have a nasty habit of falling in there and driving you crazy as they bounce around...
 
French demon said:
Do you have a picture of these hinge spring rubber insulators? I don't know what you are talking about...
Click to expand...
1727273795419.png

They're a couple of rubber sleeves that keep the springs from slapping against each other. If they're missing, a couple pieces of fuel or vacuum hose will suffice.
 
If it is actually the trunk lid inner liner hitting the outer steel sheet causing this noises you suspect, you would likely be able to feel/hear the movement of it by you simply pressing down on the lid after being closed. If there is excess movement causing noise, likely causes are bad seal, or incorrectly installed springs, hinges, latch issues, or trunk misalignment. Nonetheless you could begin checking by simply temporarily placing a few clean soft wash towels between the lid and trunk opening perimeter. This should generally rule out trunk lid movement caused noises and you would avoid all the work of actually removing the lid like you mention doing.

Also, this is not an idea for many/nowadays, but here is something we would do in the old days to quickly/easily figuring this out would be to find a volunteer to jump in the trunk while taking her out for a quick spin. They could listen to identify the cause in person. In modern times you can put a GoPro camera in the trunk, and or alternatively remove rear seat back with liner, and bring someone along to do some observing from cabin passenger seat while you drive. Good luck.
 
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If the noise sounds tinny, I would suspect that the sealer between the exterior sheet metal and the underside support bracing has separated. If the sealant has turned loose, try this experiment, fold a couple of pieces of cardboard and put it between the bracing and the sheet metal. If the noise goes away, there is the problem.
 
MOPAR4Me said:
Also, this is not an idea for many/nowadays, but here is something we would do in the old days to quickly/easily figuring this out would be to find a volunteer to jump in the trunk while taking her out for a quick spin. They could listen to identify the cause in person. In modern times you can put a GoPro camera in the trunk, and or remove rear seat back with liner, and bring along a passenger to do some observing while you drive. Good luck.
Click to expand...

As I don't have any Go-pro, I will try to find a volunteer :lol:


Demonracer said:
If the noise sounds tinny, I would suspect that the sealer between the exterior sheet metal and the underside support bracing has separated. If the sealant has turned loose, try this experiment, fold a couple of pieces of cardboard and put it between the bracing and the sheet metal. If the noise goes away, there is the problem.
Click to expand...

The sound isn't tiny. It's loud....
And it's impossible to put a cardboard piece between the bracing and the sheet metal : no opening except the ones for the wing.
20230810_104749.jpg
Sticker.jpg
 
should be 2 sleeves if I recall I have 2 on my 70 Dart I realize it isn't a Demon though...
 
Dartswinger70 said:
should be 2 sleeves if I recall I have 2 on my 70 Dart I realize it isn't a Demon though...
Click to expand...

Maybe I should have two. To avoid the upper spring to slap under the package tray.

But the noise seem louder than a spring slapping on a sheet metal.
Something like a heavy object bouncing on the trunk floor.
But my trunk is empty.
:rolleyes:
 
It could be something under the car, like exhaust etc. or something that fell down in the trunk extensions of the quarter panels...
 
Remember what I said the spare tire holds the gas tank tight. The straps holding the tank are mounted to the brace on the bottom of the spare tire well. The long bolt for the spare tire pulls up on that brace using the spare as the support. That is why driving with a full tank of fuel without a spare fastened could cause the tank to drop. And if the well floor is rusted the tank falls out. Also check your top shock mounts in the trunk . Or it could be the tail pipe hitting the tank or the frame,
 
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I tried to push and pull the gas tank up and down, but it doesn't move at all.
The exhaust pipe and muffler don't touch anywhere and the shock absorbers are brand new.
My trunk floor is healthy
IMG_20200815_151926.jpg
DSC_0570.JPG

I really don't know where this noise comes from.
I will try to add another sleeve onto the torsion spring of the trunk hinges.
 
French demon said:
Hi all,

For a long time now, I hear a loud noise in the trunk while driving, especially on bumpy roads. Like if an heavy thing was bouncing into the trunk.
It is very unpleasant
Despite my searches, I didn't find where this noise comes from.
It's not the spare tire, jack or tools, not the exhaust, not the gas tank, not the rear seat, not the package tray...

I suspect my trunk lid. I have the early flat model, the one without a rib in the middle.
View attachment 1716307714 I
The lid is in an excellent shape, but is it possible that the inner liner hits the outer steel sheet causing this noise..?

I will try driving with the lid removed, but wanted to know what you think about that?

Cheers... :)
François
Click to expand...
New Shocks? I've had new parts be defective or fail. I would look at them again if you can't locate the noise
 
Cause to the noise, I thought of faulty shocks and I replaced them some weeks ago (during springtime). But with both the old or the new shock absorbers, the noise was and is still there.
 
Here's what happens when I push with my thumb on the trunk lid.
The smooth outer metal sheet is elastic. It's noisy and also hits the inner bracing (the space between them is thin, maybe 2 or 3mm)
The median rib on mid '71 trunk lids is probably how Chrysler fixed the problem.



Now, how correcting this problem?
I though about using expansive foam but there's no way to access the noisy area.
Noise.jpg

Another solution : drilling a little hole into the sticker and the inner sheet. Sticking a nut and with a screw, slightly pushing onto the outer sheet to immobilize it and by the way turn it silent.
I don't know if I'm very clear but I do not see any other solution.
 
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If your going to drill a hole and if you use expanding foam you may get a bulge on the outside. If use used silicone caulk to pump in that might quiet it.
 
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