Join Date: Nov 2011
Location: Houston, TX
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Well, I have not done ANY of what I am about to mention YET, but here is what some of my reading and research has turned up. And while still a n00b to diesels, I'm not a stranger to cars, trucks and turning wrenches.
Most people that I have read about use Dynamat or something similar, either a competitors product or "peal & seal" type stuff which you can get a Home Depot or a hardware store. Peal and seal seems to work well enough and is much cheaper, but is not meant for enclosed spaces and stinks for a while. The smell does seem to go away but a lot of people are afraid to use it because of chemicals that are emitted when it heats up, can't say I blame them to be honest. Dynamat seems to work the best, but it is expensive. I have heard something called FatMat makes a good alternative and IS made for use in your car.
In addition to the stick on mats there are heavy composite metal plates, also sold by dynamat and others probably, that can be added to the middle of doors and panels to dampen vibrations and help reduce resonance. For this, a small piece in the middle seems to go a long way.
There are also sound dampening mats to attach to the underside of the hood. You can spray the underside of the cab with bedliner. There are heat resistant, sound damping sprays (lizard skin comes to mind) that you could spray the firewall with, probably in the engine compartment and inside the cab if you wanted to. You can go old school and use plain mass to absorb the sound with a sheet of lead if you can find it. A layer of that on the floor under the carpet and up the firewall should do a good job of blocking road and engine noise, but I have no data on how much and how thick the lead would need to be. A spray-in liner in the bed is supposed to quiet down some road noise from the back of the truck as well.
I have plans to improve the sound insulation in my truck this year, have some transmission and clutch issues to fix first though. But here is what I am going to do on my ride.
1 - Door seals. Either replace or the door seal mod with tubing
2 - Dynamat or FatMat in the doors, maybe use some of those metal plates in the middle too
3 - Dynamat or FatMat up the firewall. I may try to take the dash off to get up higher, have not decided yet. A number of people say this is easy but it looks like a PITA to me.
I may do the floor as well, more for heat shielding than noise and because I am going to take the carpet out to clean it anyway. I have heard that the under hood mats work pretty well but have not looked into them much myself. It seems that using the dynamat on the floor gives little return and the roof even less. Most of what I have read is that the two main sources are engine noise through the firewall and road noise through the doors and gaps in the door seals. You can do more work on the rest of the truck but it is hard to block out enough engine noise to notice the road noise coming through other areas.
FWIW, hope this helps. Helped me to write it all down if nothing else...