gearbox sound insulation.

[pfenlon]

As far as I know, the insulation for the gearbox on TR cars has been over the top of the tunnel and also the carpet over the chosen insulation.

On my 64 MK1 Spitfire 4 I brought over from California, which was Bog standard, I found what can only be called a Bag (plastic) stuffed with some sort of insulation material,

which just seemed to rest on top of the box.  Must have been an ST thing,  if it worked???, I wonder why they didn't use it on the TR cars, I have a fibreglass tunnel, and looking for an

insulation to quieten the revolving mechanicals.

[John Morrison]

Hi Pete,

How are You?

Becareful what you fit, I had something similar to what you describe,

and itcame instuck, and knocked an inhibitor switch connection off.

John.

[MilesA]

21 minutes ago, pfenlon said:

As far as I know, the insulation for the gearbox on TR cars has been over the top of the tunnel and also the carpet over the chosen insulation.

On my 64 MK1 Spitfire 4 I brought over from California, which was Bog standard, I found what can only be called a Bag (plastic) stuffed with some sort of insulation material,

which just seemed to rest on top of the box.  Must have been an ST thing,  if it worked???, I wonder why they didn't use it on the TR cars, I have a fibreglass tunnel, and looking for an

insulation to quieten the revolving mechanicals.

Pete

Recollection a bit hazy but I think the 'Bag' went inside the gearbox tunnel on my old Spitfire. Someone may here may be able to confirm though....

Miles

[Spit_2.5PI]

Yes, the fibre-filled bag sat on top of the gearbox in the Spit. It's my belief that it was there as heat insulation (it would be nearly transparent to sound), and that sound insulation was provided by the "cardboard" tunnel itself plus the carpet on top.

Cheers, Richard

[Chris Bottomley]

On the original fibre tunnel on my GT6 the insulation in the plastic bag was stapled onto the inside of the tunnel moulding. I am pretty sure that this was the standard Triumph installation, the Bond Equipe I had in the early 1970's had the same insulation.  On the GT6 I replaced it with SilentCoat insulation sheets on the inside of the tunnel, it seemed quieter and cooler afterwards.  I used the same type of insulation sheets on the inside of the plastic tunnel in my TR6.

[Nobbysr]

Having owed a GT6 mk2 for many years I can confirm that there was a sealed bag of insulation which was  almost like saddle bags  where it was  taped to the inside of transmission tunnel to sit either side of the gear box . Its a double edged sword as if you  remove it  the interior  gets hot in summer and gear box temp increases. The gear box on spits and Gts all run hot  and the oil looses viscosity very quickly. The first thing i did was  i fitted  a larger main-shaft  tip fitted and the first motion shaft opened up to take a larger needle and bearing  and i fitted an oil cooler  the noise reduced and the overdrive  worked better. These bags often became oil soaked and fell onto the exhaust so i dumped mine and fitted modern isolation pads. One thing i did do one my 3A is have the extractor manifold and the pipe from the manifold to the first box ceramic coated and the temperature was reduced by 15 Celsius with better combustion  i wish it had been around when I had the GT6 .. the car was modified  running 1 3/4 strombergs, with a full stage 2 lightened and balanced engine and 1500 Spit Diff and i really regret selling it

[Darranh]

Likewise on my 71 Herald 13/60. The plastic bag was on the inside. They do virtually no good for sound insulation. The contents are light weight, they settle to the bottom of the bag and ideally need to be in contact with the underside of the tunnel. On my TR4 to reduce noise vibration and harshness I fitted mass load vinyl to the fibreglass tunnel (and the rest of the floor pan and back of fuel tank) and then waterproof foam to the outside before fitting the loop pile carpet. Works a treat keeping the high frequency mechanical noise out of the interior. 

[pfenlon]

On 11/22/2020 at 10:46 AM, MilesA said:

Pete

Recollection a bit hazy but I think the 'Bag' went inside the gearbox tunnel on my old Spitfire. Someone may here may be able to confirm though....

Miles

Thats what I meant Miles.

 

[trevor]

When I fitted my new 2-part tunnel I lined the inside with heat insulation mat to keep the heat out of the cabin , guess it’s helping with noise as well.