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Gearbox tunnel - sealing, heat and noise insulation

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Sealing, heat and noise insulation on my GT6 gearbox tunnel. 

Plastic (vac formed, not injection moulded) tunnel from Rimmer Brothers. 


Lined, 100%, with 12 mm thick Pyrosorb-S is a class "0" accredited cellular acoustic foam. Safe and easy to install. Includes self-adhesive backing. 


Then skinned with Aluminised Heat Barrier

Flexible high temperature insulation. 

Woven glassfibre sheet laminated to heat reflective aluminium foil. Approx 1mm thick. 

Used Heat Resistant Adhesive from Woolies: Alphabond AF178 High heat resistant.

Rated up to 120 degrees centigrade. 

Ideal for vinyl roofs, headlinings and lining carpets. 


All gaps in the heat barrier are taped over with 3M 1436 Aluminium Foil Tape - 50mm x 50m.  Ref17:  MI-3M-1436-50 

Aluminium foil combined with high tack rubber adhesive and easy release liner. Holds and seals on a variety of surfaces. Offers excellent flame, moisture, weather and chemical resistance for a variety of demanding applications in aerospace, automotive, marine and many other segments. 

Seal to body changed to SRS15, Sponge Extrusion 'U' Section, 16mm (5/8") wide 14mm (9/16") tall. 

Stuck to tunnel with Loctite ???? Superglue. 


Rear seal to prop-shaft tunnel: 

Used same SRS15 sponge extrusion and Loctite ???? Superglue, water and heat resistant. 



James Paddock tunnel fitting kit (JPR919FK) 

Two screws added (per side) for fastening to bulkhead. 

Oil fill/level plug: 

From bulkhead - 6”. 

From floor top face - 2”. 

I’ll upload pictures later on. 

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If your taking that much trouble to keep heat out of the cabin, chek that ALL the many holes in the bulkhead are sealed, and that the cover seals well.

ALL the heat comes from the radiator as hot air, NONE from the gearbox and exhaust pipe, and I can prove it!


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Good job! I'm also going to insulate the bulk head to cover all the holes! I'm told bulk head insulation cuts noise by 2db. Might have been JohnD said that, can't remember. :wacko: Got to find a way to get the rubber boots on top of the clutch and break pedals back into their mountings. 


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Sound insulation?  Not me.

How will you insulate the bulkhead?

There are three ways that heat travels, Radiation, Conduction and Convection, and the gratest of these is convection.     Radiation is stopped by a sheet of paper, metal is a good conductor, but as any one knows who goes out on a cold, windy day, the "wind chill factor" can make it appear much colder than it is.     The radiator produces vast amounts of hot air that will find its way into the cabin through holes or gaps, but if they are sealed, it won't!    The holes don't need welding up, just filling with a durable rubber grommet, seal strip or similar.    I suppose that a layer of plastic insulation sheet would be as good a blockage, but a LOT more expensive!



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I'll use Silent Coat on the bulkhead same as the inside of the tunnel, I bought too much for the tunnel so I'm going to use it. My main concern, as you say, is covering holes and the SC does the job. And I think some olive oil on those troublesome rubber boots.


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