I guess this very well could be my first real mod on my 4runner other than putting on a rack or getting FJ Cruiser Trail Edition black wheels. So, a little bit of background before I start. I'm kind of weird. I only drive manual transmissions, and after searching high and low for a few months I came across my 1999 Highlander, black with grey leather interior. I purchased it from another member on T4R. Hooray for the Internets. Boo on Toyota for stopping production of manual transmission 4runners for the US in 2000.

I read a story one time about an elderly man in Canada that went to rent a car and the rental agent had to teach him how to drive an automatic because, although he was in his 80's, he had never driven an automatic before. Only manual transmissions his whole life. I could be that guy. I'm that weird.

I've decided that my 4runner pretty much has to be my forever car, and very well may be the last manual transmission 4x4 I ever have the pleasure of driving. That means I'm entitled to spend stupid amounts of money on a vehicle that is 14 years old, and has a street value of less than $10k, right?

First (money sink time waster) project up is turning this thing from tin can into silent vault. Right now with the Highlander suspension, I hear every boom, bang, clank, and shudder the road has to offer. Toyota did a really crappy job of sound insulating the rear half of 4runners, and the stiffer suspension adds to the drama. I'm going to fix that.

If you have any suggestions, questions, or comments, please let me know. I'm not an audiophile, but am pretending to be one at the moment. Your help will be much appreciated. And I also have no experience doing this, so I'm expecting the results to be amateurish and comical (or totally awesome).

I'm dividing this process into 6 steps as outlined below. I will create a post for each step. I will document how I perform work OR provide links to where I was able to learn how to execute whatever steps are necessary. No reason reinventing tutorials that are already available.

Step 1: Baseline Testing
Step 2: Material Selection
Step 3: Vehicle Prep
Step 4: Installation
Step 5: Vehicle Reassembly
Step 6: Performance Testing

Reference Posts

Vendor List
Soundproofing Build Threads and Tutorials


Also a quick shoutout to Skidmarcx. His soundprofing project was inspirational and can be found here.

Purpose: Determine performance of stock sound deadening materials and methods by testing vehicle under normal road conditions.

Methodology: Use a sound level meter to record decibel level readings under the following conditions

Engine - No Load


Engine - No Load
Details: Using a sound level meter, 5 measurements were taken. Measurements included minimum and maximum decibels recorded over a 5 second period of time. Control consisted of measuring ambient noise inside the cabin with the vehicle turned off an all windows up. Engine was turned on and warmed up to record idle sound. Results are as follows.



It is interesting to note that the engine is actually quieter at 1500 RPM than at idle (700 rpm). Also, the engine is quieter at 3500 RPM as opposed to 3000 RPM. Guess the engine balances itself out slightly better at those RPMs.

Purpose: inventory and cost of all materials used for project.

Dampening / Resonance Reducing Products

MLV (Multi Layer Vinyl)

CCF (Closed Cell Foam)

CLD (Constrained Layer Dampening)

Misc. Supplies and Installation Tools


Note: Thanks for all the suggestions and interest in this thread. I'm going to create an inventory of potential vendors and in a reply post below. Keep all the suggestions coming!

Purpose: document all activities required to prepare vehicle for sound deadening material installation.

Purpose: Installation of all sound deadening materials

Purpose: transform vehicle back into normal working condition.

Purpose: Determine effects (improvements, detriments) of using sound deadening material over stock.

very cool.

are you going to do the $900 is parts and materials (semi-pro or pro) way?

In 2007 I did my whole interior with rubber roof liner (per Yotatech articles) and it has worked great. The cost was about $140 in materials.

The goal is absolutely to spend way too much money. I'm still investigating tons of options on materials. I came across some lead core flooring materials from Cascade Audio Engineering. Evidently that retails for about $230 for a 12 sqft roll. But yeah, tons of options I'm looking at right now. Analysis paralysis.

Excited to see your progress! I did this about 6 months ago on mine... Spent around $400 using Second Skin... Have fun!

I will hopefully have my runner rolling again by the end of the month. I will post up some "after" spl measurements when I do, so you can get a feel for the effectiveness of the materials I used.

Subscribed for updates. Im mostly curious how much the project ends up being. I would LOVE to do this, but 900.00 is way steep for me. But, if its around 300.00 then I think I could talk myself into it.

Just as you said, my 4Runner is my favorite vehicle Ive owned, expect to drive it for a long time and even plan on giving it to my kid (maybe, I might still keep it) and he is only 1.

I use the Stinger sound dampener for $120. Was enuff to do the roof and the 1/4's and some of the floor. I am planing on buying another box of it to do the rest of the floor board. But from what I can tell the noise coming from the roof and rear half has gotten quieter.

If you have a smart phone, there are decibel meter apps that you can download. Maybe this will help in determining before and after comparisons. Good luck with your project!

I used Raammat and Ensolite on my WRX and was impressed with the products. The Raammat damps panel resonances and the Ensolite decreases sound transmission.

RAAMaudio - Automotive sound deadening products

- Matt