Undercoating and decrease road noise?

[Gator Smiles]

In the Southeast, most new Toyota's have a regional installed accessory package which includes undercoating. I recently heard someone claim that a nice benefit of the undercoating is reduced interior noise due to sound deadening effect. Has anyone heard this or is my internal B.S. meter accurate.

[adjmcloon]

I have heard that undercoating will help with that, but you would also have luck double-layering dynamat (or some sound deadener) inside all of the doors. I plan on doing this with mine, because the road noise is over the top on my '04....we traded out of an '07 Tahoe and I really got used to how quiet that vehicle was. Some dynamat ought to help though.

[cheepyankee]

too bad they dont include undercoating here in the NE salt belt. I'm planning on doing it in the spring. It does seem like all the road noise comes from the wayback. I'm going to do the rear fender wells, which is the first place to rust anyway. Maybe Dynomat the tailgate.

[kathyricks]

Originally Posted by Gator Smiles

In the Southeast, most new Toyota's have a regional installed accessory package which includes undercoating. I recently heard someone claim that a nice benefit of the undercoating is reduced interior noise due to sound deadening effect. Has anyone heard this or is my internal B.S. meter accurate.

Undercoating does little to quell road noise. It does, however, help a smidgen to quell body vibrations. An outstanding undercoating is Henry Plastic Roof Cement which you can buy at Home Depot. It stays slightly flexible and won't crack for years. On Toyota's most of the road noise comes in through the doors because Toyota uses plastic door panels and doesn't use any, or hardly any insulation in the doors. So the doors need a sound ABSORBING material (not dynamat which is a sound barrier material) glued to the inside of the door skin. The best material for this purpose is 3M Thinsulate Accoustic Insulation, but it's not available to the public. The second best material is compressed fiberglass acoustic panels. They're available on ebay, but are 1 inch thick which is too thick for some doors so sometimes you have to cut them back to 1/2 inch. Alternatively, you could use water heater fiberglass blanket material available from Home Dept. The third best material to use is cotton shoddy padding. It comes in rolls on ebay and sometimes in home depot and is sold as either a water heater blanket or as an underhood engine compartment blanket.

[darryl-3]

Much of the noise you hear when driving comes from the pillar areas, which are rarely sound insulated. They channel noise to the upper part of the truck. High end cars usally use expanded poly (much like the thinsulate above). Ive used heavy shoddy pad (shreaded cotton fiber) or spray foam. Use in the A-pillars (between the windshild and drivers door) and B-Pillars (Between the front and back doors) if you really want to quiet things down.

[indycar89]

Originally Posted by darryl-3

Much of the noise you hear when driving comes from the pillar areas, which are rarely sound insulated. They channel noise to the upper part of the truck. High end cars usally use expanded poly (much like the thinsulate above). Ive used heavy shoddy pad (shreaded cotton fiber) or spray foam. Use in the A-pillars (between the windshild and drivers door) and B-Pillars (Between the front and back doors) if you really want to quiet things down.

So you drill into them or what?

[darryl-3]

If you remove the interior panels, B-pillars usally have access due to seat belt clearance holes etc, A pillars on many cars have grab handles holes or wire harness holes or sunroof water drain or for antenna's / onstar etc. you can gain access. Most all have holes for attachment of the interior trim.

For the shoddy pad just cut and attach it to the inside of the interior trim, hot melt glue (high temp) works just fine for this app. Put spots of glue on the panel and them press the shoddy onto the glue.