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  •  » Early Fastback - Trunk Area Sound Deadening

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    6/10/2022 11:47 AM  #1

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
    Posts: 2,210

    Early Fastback - Trunk Area Sound Deadening

    At highway speeds, with windows closed, the interior road noise coming from the rear is fairly high.  I want to install sound deadening in the trunk area of my fastback with a fold-down rear seat.  I believe with the fold-down rear seat, noise from the trunk area is more severe than w/o the fold-down seat, and also the coupe.
    So, when applying sound deadener in the trunk is it best to cover the entire trunk area or is some limited area (like the wheel wells) provide enough dampening of road noise.
    I am wondering other owners experience with reducing road noise at highway speeds. 

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    6/10/2022 3:58 PM  #2

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 11,746

    Re: Early Fastback - Trunk Area Sound Deadening

    Top of gas tank and floor of trunk

    Top of area over the differential.

    Wheel wells and backside of interior quarter panels.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    6/10/2022 4:55 PM  #3

    lowercasesteve
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    From: Auburn, Ca
    Registered: 4/01/2013
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    Re: Early Fastback - Trunk Area Sound Deadening

    I recently installed a Dynomat kit for my trunk.  It is as MS says - top of gas tank, above diff, wheel wells, and on either side of gas tank.  It was easy to install.  I also did the doors in another kit.  These kits only cover partially, and Dynomat says that is enough.  I have noticed a definite reduction in noise, but do not expect vast noise reduction, as there are a bunch of other sounds around - like tire noise, other cars/trucks, engine noise, mufflers, and the squeaks and rattles of a 50 year old car.

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    6/10/2022 10:48 PM  #4

    Nos681
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    From: Atlantic Mine, Michigan
    Registered: 7/14/2016
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    Re: Early Fastback - Trunk Area Sound Deadening

    I used ACC sound dampening material in my coupe.

    It is an asphalt type non adhesive…think shingles without the intentional rocks.

    Layout in sun for short period and will form easily.
    Can be stiff/crack in cold weather.
    I used it for cost and works for a driver type car.



    Another option is a rubber mat, kinda like the “WELCOME” mat.

    Tractor supply has large rubber mats for trailers /stalls for animals, about 1/4” thick.
    I used some to dampen the noise inside the aluminum truck cab of work truck.
    It reduces the noise, fleet decided to mount sliding drawers in interior…too noisy for me.
    Only problem I noticed in work truck, can still smell rubber on warm days or if heater starts warming up cab.

     

    6/11/2022 6:15 AM  #5

    Dkralc
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    Registered: 12/26/2015
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    Re: Early Fastback - Trunk Area Sound Deadening

    Asphalt based sound deadeners will smell like tar when they get hot.  Use a butyl based like Quadmat no odor.

    Last edited by Dkralc (6/11/2022 6:16 AM)

    www.quadmat.com  Butyl Sound Deadener & Insulation
     

    6/11/2022 6:33 AM  #6

    Don
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    From: Coppell, Texas
    Registered: 4/02/2013
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    Re: Early Fastback - Trunk Area Sound Deadening

    I did sound BLOCKING.   NOT just dampening   3 steps   1) for stopping vibration induced freq. Spread out  10 percent area Sound Dampening (ie Dynamat)  2) for blocking  low freq,,, e layer   =13.3333pxMass loaded Vinyl (MLV) - 1lb - Acoustic Barrier, Blocks Noise, STC Rating 26, Made in USA, 4'x10' roll 3) for high blocking freq a density foam on top of vinyl Lazy Dog Warehouse Neoprene Sponge Foam Rubber Sheet Rolls - 36in x 60in (1/8in Thick)  Then after this on floor I installed a rug with heavy backing material ( did this because just needed new rug and  cost affective) YES major job to do.   Think cocoon.  I did most areas and is still a work in progress, lots of small area need attention. Changed TA radials to Continental Extremes for modern tire noise reductions built into design.      Test results at HW  75 mph  ish ,,road surface changes,   dB levels.     Before 79 db  -- 82 dB.  Now 72dB -- 76 dB.  over same roads. Still more work needed but (T).    NOTE  MY personal loud old rock n roll music NULLIFIES everything,       

    Last edited by Don (6/11/2022 6:43 AM)

     

    6/11/2022 1:03 PM  #7

    DC
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    From: Marshall, MI
    Registered: 4/01/2013
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    Re: Early Fastback - Trunk Area Sound Deadening

    I used a foil covered stick on dense material and was happy with how much it helped.  Covered trunk floor, gas tank and all the flat surfaces in trunk and whole floor inside car. BUT, no one notices since I got no mufflers and I drive like I do!

     

    6/11/2022 5:35 PM  #8

    6sally6
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    From: Surfside Beach,SC
    Registered: 4/02/2013
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    Re: Early Fastback - Trunk Area Sound Deadening

    DC wrote:

    I used a foil covered stick on dense material and was happy with how much it helped.  Covered trunk floor, gas tank and all the flat surfaces in trunk and whole floor inside car. BUT, no one notices since I got no mufflers and I drive like I do!

    Great minds think alike!!!!!!!!!
    6sal6
     

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    6/12/2022 8:56 AM  #9

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
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    Re: Early Fastback - Trunk Area Sound Deadening

    Thanks to everyone for the advice. 
    Last year, I placed “Noico” Sound Deadening (80mil) across the area above the rear differential and it made a big difference to the noise level.  And I had already placed the “Ford” style OEM insulator above the gas tank.
    I’ll finish off the trunk floor, what I can reach in the wheel wells and quarter panels from the trunk.  If I need to do more, it will become a Winter project to pull the interior apart to reach those places I can’t get from the trunk.
    Thanks again.

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
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