I posted a similar thread in the Sierra forum, but this one is much more visited. So here goes....
1.) Got a newborn and the 35 inch Toyo M/T's are a lil loud rollin on the highway when we go to visit grandma. Plus it would be nice if the cabin of my rig where just plain more quiet. Does anyone have experience with Dynamat? Ive ordered two door kits, and I'm gonna start there to see if I get any results before I gut the interior of my rig and do the floors, firewall and backwall. Everything I have found so far says that its a great product and people are happy with the results produced.

2.) Another thought: I ripped this idea off Magna Charger from their supercharger install instructions. They have a step in the install that says to fill the fender with Touch 'N Foam, which is a home improvement all-purpose insulating foam. They claim that this is to drastically reduce noise, most likely around the intake from the compressor of the supercharger. My thought is that this would aid in damping unwanted noise from the road, or at the very least, from the engine compartment. Any thoughts on negative effects from this foam? (im scared it will expand for some reason and blow the fender out, who knows).

 

I did that in a hollow core steel door one time and it pushed the skin out. I wouldn't risk it if it were me.

 

Magna Charger seems to think its alright. How strong is this stuff? It seems unlikely that foam would win against a metal fender.

 

I"d go dynamat over the spray foam. The foam is hard to control where it"s going to go and what it"s going to stick to.

 

the foam is in addition to the Dynamat. Im just not 100 percent confident it wont damage something.

 

I wouldn't do it. Knowing my luck I would cover up something I needed to get at like wires or something or get in a fender bender and the damage being much worse since the foam wouldn't allow the fender to collapse. Just a thought.

 

...or a steel door...

I'm sure you could do it if you just did a little at a time.

 

I'd worry more about fixing the fender after. I don't immagine it would be any fun to try to do sheetmetal work on a fender full of foam.