Sound deadening for back wall of cab recommendations?

I know better than to block/plug cab pressure vents, but… Has anyone had any success with muting/muffling the noise from them?

I will be applying sound mat to the back wall soon, but with so much noise coming in through the vents, I wonder the point.

 

Many here do the "noodle mod", which is simply a pool noodle or 3/4" pipe insulation stuffed between the cab and truck bed. It doesn't completely block air coming out of those vents, but it does muffle noise. I have not personally done it, but it's on my to-do list.

Some people have applied sound dampening material over those vents but punched small slits in the material to allow pressurized air to move through.

 

From what I have read of the “noodle mod”, people either have zero problem/consequences, or corrosive damage to the cab. I’m thinking of re-engineering the results of said “noodle mod” while minimizing the downside. In addition to an exterior mod, I am curious about any successful muffling interior mods.

 

I noticed the pad that was attached to the back wall covered most of the vents as is(2/3). I traced some MLV and kept the same profile as the pad. The MLV was placed over the pad and I used the same attachments. It’s much quieter even with leaving some of the vent exposed.

It’s worth it to take the side seatbelt trim off and place some padding/mlv in there as well. Toyota has a TSB for rear diff whine and this is one of the steps in addition to cab mounts.

 

Did you happen to take pics during the process?

 

Thank you Jassco!

Do you have a preferred source for MLV?
I found this…but it seems a little expensive…
https://www.soundproofcow.com/product/quiet-barrier%C2%AD-md-soundproofing-material-sheet/

Do you have any pics of what worked for you? (Your description gives a pretty good idea, but pics always help)

 

I covered the back wall and rear floor with Dynamat and Siles 3/8" thick closed cell foam. I did not cover up the flap for the ports, but I did follow the outline of the OEM sound deadener that was there. Huge drop in road noise. But the flaps still make noise.

 

I used killmat on the all of the truck interior, I then put a layer of closed cell foam with an adhesive on one side. The plan was for MLV all over the truck but so far I have yet to figure out what strategy I will use on the aft doors. (Access Cab)

I then constructed a guard grill for the 2 aft vents using the mesh material from an old air filter. This is to prevent any foreign object from going inside the vents and getting stuck. I then put 2 layers of air filter foam over the vents as well as in between the upper and lower channels on the aft wall. This is to dampen the sound and still allow air out. I then used 1/8 mass loaded vinyl to replicate the blanket on the aft wall. I don't have a picture of my blanket installation.

Be aware that reassembly is long and painful when you add any thickness behind the interior panels. I originally made a MLV panel to go over the vents but I couldn't get the panels to clip in due to the added benefit thickness off the material.

I have yet to drive the truck since I am still reassembling and doing other mods but I will comment further once done. I did take a sound reading prior to adding all the sound deadening and soundproofing material so should be able to provide a before and after reference.

 

I'm in the middle of sound deadening my 2nd Gen and have been contemplating the air vent problem. What great timing! Your idea to use air filter material is brilliant. I'd like to bounce this idea off of you though..

The goal is to completely block noise, but leave the vents unobstructed to air flow. We want air to be able to flow in order to alleviate pressure changes, but we don't want to let sound in (which also happens to be pressure changes, albeit at MUCH higher frequencies). To solve this conundrum, could we place a "slab" of mass loaded vinyl (MLV) directly over the vents, but cut a "flap" that can freely "pivot" (like a doggy door) to allow air flow? The flap would allow air flow when subject to constant pressure changes, but would essentially not move at all in response to oscillating sound pressure.

Does anyone see any downsides to this? I understand these vents have something to do with humidity control, but I don't fully understand how? Would this solution inhibit this function of the vents?

 

I've used Resonix products before and will be doing so in my Tacoma in the coming month or two. The stuff is pricey but worth it. Nick is also a good dude, very helpful. https://resonixsoundsolutions.com/
https://resonixsoundsolutions.com/sound-deadening-materials-reference-information/

 

The flap would have to flap in both directions. I would think mostly they would have to “flap out” to allow the air to push out.

 

Sound waves just superimpose on the “constant pressure”.

 

Usually to block noise you create a full seamless barrier. Another option is to create lots of obstacles to diffuse the sound. Our issue with the tacoma is the width we have to work with to dampen the sound.

My first attempt to build a MLV barrier over the vents and then let the air go through the sides of the aft panel failed. The rear panel has a bit of room behind it but it also has numerous "standoffs" that index the panel and help with stabilization of it . When I tried to reinstall the aft panel, I couldn't get any of the red plastic clips to clip in... The MLV gets in the way.

I ended reproducing the thin oem aft panel sound damper with thicker MLV. I have butyl sound dampening material on the aft wall, a light closed cell foam over that and then I installed a metal grill over each vent. I then made a foam piece that air needs to go through that covers both around and in front of the air vent. The cabin is way more quiet but I can still hear some rear tire noise.

Maybe the foam tube between the bed and cab would help...

 

In other vehicles, I have found that using a “spray in bedliner” material to line the wheel wells helps considerably with rear tire noise.

 

Second Skin Damplifier Pro 2mm

 

I used cheap Amazon brand noise dampening on my back panel. all adhesive backed sheets. I noticed a little bit of an improvement in road noise.

$30 Amazon Basics Car Sound Deadening Mat, 14.5" x 10", Pack of 10

Amazon.com: Amazon Basics Car Sound Deadener, 14.5″ x 10″, (10 count)Pack of 1 : Automotive

 

I’m dealing with this issue now. I have a rear goose gear seat delete and today I did Kilmat and Siless foam pads on the entire rear wall:



I ditched that carpet like flap that was held up with plastic clips. I was all excited after I re-installed the goose gear back wall, went for a drive and I swear the cab is louder than before all the sound deadening material. Anyone have any advice? Do I need to put that OEM carpet-y mat thing back on?

It seems to me that the wind noise from the vents is far more noticeable now than it was before the sound deadening.

 

I know having the back seats in the upright position does a lot to muffle road noise vs having them folded down. By removing those seats you've lost a lot of insulation.

 

That or something equivalent. Most of the noise comes through the vent.

 

i tried that based on what i read at TW and i found it did nothing for me. I removed it to prevent it trapping grime and promoting paint damage since it was not doing anything for me.