lightning

lightning

Well-Known Member
So, my 110 CSW is actually fairly quiet for a Defender.
At 65mph it's showing 80-85db on my meter.
I wonder if l can make much improvement on this. I already have under bonnet soundproofing, soundproofing mats on top of the seat box, and also on exposed metal surfaces under the back seats.
Plus it seems to have fairly heavy duty carpet as standard on the floors and transmission tunnel.
l've got heavy rubber floor mats over the carpet in the front and rear.

l wonder if any further noticeable improvement can be made. l've seen adverts for dynamat footwell and seat box insulation amongst others and it's not cheap.

I've checked with a db meter while driving and the noise comes from everywhere, particularly the transmission tunnel.

The foam pad is in place under the rubber gear lever gaiter, but does anyone do a shaped transmission tunnel soundproofing?

And is it worth putting soundproofing in the foot wells? (on top of what's already there)

I put the Defender in neutral at 70mph and let the engine idle, noise levels inside didn't change much maybe 2db on the meter.

l don't want to waste hours taking all the interior out to fit £300 of sticky back dynamat if it's not going to do much.
 
lightning said:
So, my 110 CSW is actually fairly quiet for a Defender.
At 65mph it's showing 80-85db on my meter.
I wonder if l can make much improvement on this. I already have under bonnet soundproofing, soundproofing mats on top of the seat box, and also on exposed metal surfaces under the back seats.
Plus it seems to have fairly heavy duty carpet as standard on the floors and transmission tunnel.
l've got heavy rubber floor mats over the carpet in the front and rear.

l wonder if any further noticeable improvement can be made. l've seen adverts for dynamat footwell and seat box insulation amongst others and it's not cheap.

I've checked with a db meter while driving and the noise comes from everywhere, particularly the transmission tunnel.

The foam pad is in place under the rubber gear lever gaiter, but does anyone do a shaped transmission tunnel soundproofing?

And is it worth putting soundproofing in the foot wells? (on top of what's already there)

I put the Defender in neutral at 70mph and let the engine idle, noise levels inside didn't change much maybe 2db on the meter.

l don't want to waste hours taking all the interior out to fit £300 of sticky back dynamat if it's not going to do much.
Click to expand...

When I done the rebuild, I put silent coat on everything I could, apart from the foot wells as I don’t have carpet to cover it and didn’t want it in the engine bay. I think the biggest single improvement to sound deadening came when I done the doors. I only used silent coat on mine, but also used a sound absorbing mat on the Puma. It made a huge difference to the doors closing (never been it while it was driving though).

The gearbox tunnel is easy to remove if you want to coat the underside, I have, but not sure how much of a difference it’s made.

I read a lot of threads about noise reduction when rebuilding mine, one thing that came up was to use some 10mm foam along the edges of the bonnet. It seals the wings and apparently made a massive difference. I will see if I can find the thread and link to it.
 
lightning said:
So, my 110 CSW is actually fairly quiet for a Defender.
At 65mph it's showing 80-85db on my meter.
I wonder if l can make much improvement on this. I already have under bonnet soundproofing, soundproofing mats on top of the seat box, and also on exposed metal surfaces under the back seats.
Plus it seems to have fairly heavy duty carpet as standard on the floors and transmission tunnel.
l've got heavy rubber floor mats over the carpet in the front and rear.

l wonder if any further noticeable improvement can be made. l've seen adverts for dynamat footwell and seat box insulation amongst others and it's not cheap.

I've checked with a db meter while driving and the noise comes from everywhere, particularly the transmission tunnel.

The foam pad is in place under the rubber gear lever gaiter, but does anyone do a shaped transmission tunnel soundproofing?

And is it worth putting soundproofing in the foot wells? (on top of what's already there)

I put the Defender in neutral at 70mph and let the engine idle, noise levels inside didn't change much maybe 2db on the meter.

l don't want to waste hours taking all the interior out to fit £300 of sticky back dynamat if it's not going to do much.
Click to expand...

Couldn’t find the post, but found a part number for a genuine seal. Maybe it will help?

upload_2021-3-4_9-7-20.png

item #16
 
Thank you that's really useful, l've never seen that seal in a Defender bonnet, maybe it's ROW specification

EDlT
Fitted to early 90/110 and now appear to be obsolete but some suppliers have stock, however the rubber strips are £85 each !!
 
Last edited:
Putting dynamat all over the place doesn’t do much. It just stops flat panels from creating noise but doesn’t actually block noise coming from the engine, outside, etc. If you’re looking to insulate the cabin follow the instructions on this site (https://www.sounddeadenershowdown.com) but it’s quite involved. I did my whole bulkhead while I had the dash off and it certainly reduced the engine noise getting in but also made me realise how much noise is coming from elsewhere.
 
lightning said:
Thank you that's really useful, l've never seen that seal in a Defender bonnet, maybe it's ROW specification

EDlT
Fitted to early 90/110 and now appear to be obsolete but some suppliers have stock, however the rubber strips are £85 each !!
Click to expand...

you could probably just get some generic rubber profile strip and rivet it on. Maybe that P shaped stuff
 
Twinnie said:
Putting dynamat all over the place doesn’t do much. It just stops flat panels from creating noise but doesn’t actually block noise coming from the engine, outside, etc. If you’re looking to insulate the cabin follow the instructions on this site (https://www.sounddeadenershowdown.com) but it’s quite involved. I did my whole bulkhead while I had the dash off and it certainly reduced the engine noise getting in but also made me realise how much noise is coming from elsewhere.
Click to expand...

also with a flat panel you don’t actually need to cover the entire thing. A big square of the dynamat in the middle stops the panel vibration and harmonics
 
That’s a nice shout with the bonnet seal - I did t even think of that.
Op I did similar to gent above. I haven’t done seatbox or rear yet but did all bulkhead and front floor and trans tunnel in silent coat and then put some bridge waterproofing membrane ontop which was just thin rubber sheet. Also did the silent coat under bonnet sheet which was more like a sponge. I did this ontop of normal silent coat. The difference was really noticeable.
Also have an Ashcroft gearbox with an extended ratio 5th which I’m bloody chuffed with :p
Biggest noise I notice now is the rear - when mud pings off my wheels it sounds like it’s inside the car! I’ll be ripping rear out and doing the rear on silent foam then ‘acquired’ some thick, probably 2 inches, closed cell foam which I’m going to put under the headliner when I re carpet that.
When people say say deadening is a waste of time they haven’t done it right as mine was massively different just from doing half the car!
 
Oh I did that thick closed cell foam in trans sticks opening too to shut it off if that makes sense!
 
resto_d1 said:
That’s a nice shout with the bonnet seal - I did t even think of that.
Op I did similar to gent above. I haven’t done seatbox or rear yet but did all bulkhead and front floor and trans tunnel in silent coat and then put some bridge waterproofing membrane ontop which was just thin rubber sheet. Also did the silent coat under bonnet sheet which was more like a sponge. I did this ontop of normal silent coat. The difference was really noticeable.
Also have an Ashcroft gearbox with an extended ratio 5th which I’m bloody chuffed with :p
Biggest noise I notice now is the rear - when mud pings off my wheels it sounds like it’s inside the car! I’ll be ripping rear out and doing the rear on silent foam then ‘acquired’ some thick, probably 2 inches, closed cell foam which I’m going to put under the headliner when I re carpet that.
When people say say deadening is a waste of time they haven’t done it right as mine was massively different just from doing half the car!
Click to expand...

Spray the underside of your rear arches with a thick coat of wheel arch liner spray?
 
l've done some investigation today and it seems that if there is already reasonable soundproofing (such as heavy carpet) then there's little benefit from adding any more.
For instance noise levels in the drivers footwell (vehicle stationary, engine idling cold) with no rubber mat or carpet were 74db
With a mat it went down to 71db, with a carpet around the same.
With a mat AND carpet, around 71db

Putting sound proofing material on top of the metal transmission cover under the centre cubby box reduced sound levels in the vicinity by around 2db
Using sound proofing on both sides of the cover was similar...2db

However, there was a significant 3db drop in noise level (actually noticeable while driving) from using a carpet and rubber mat on the second row floor, rather than just a carpet or mat on its own.
(db meter on top of the cubby box with the microphone facing the rear)
Under bonnet soundproofing pads made no measurable difference to noise levels with the scuttle vents closed, but with them open it was about 1db
Every little helps!
l've ordered some rubber D seal for the bonnet/wing gap and will report on that when l've fitted it.
 
Last edited:
Awesome. Do share when you’ve got it. You should definitely silent coat the bulkhead if you haven’t! Just do it when you have to take out the dash for something else!
Mines not even noisy under 50 compared to other older trucks/tippers lol. I tell you what though, d1 ratio transfer box or a long 5th is a huuuge difference. 70 on dual is happy enough and no stress. I have music loud though and if I had a passenger without it loud it would probably seem noisy. It’s a selfish motor in more than one way!
 
Well worth doing what you can to get a drop of 2 or 3 dB. It doesn't sound like much but a drop of 3dB halves the power level or doubles the amount of time it takes for noise to damage your hearing.
 
Today l fitted some D strip along the sides of the bonnet.
This reduced noise levels around the front wings by around 2db. Not sure if that was worth doing.
However, putting some D seal along the rear edge of the bonnet (between the bonnet and scuttle panel below the vent flaps) reduced the noise levels by around 10db measured at the rear of the bonnet.
This made a noticeable difference to noise levels when driving with the vent flaps open and a smaller but still measurable difference (around 3db) with them closed.

That was with the sound level meter on the dashboard.

So, l would say not sure it's worth bothering with the bonnet side seals but adding D seal to the rear of the bonnet made a worthwhile improvement that you can actually hear when driving.
 
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