68 3/4 speed trans tunnel insulation installation

[David M.]

Anyone have any info on how to go about installing the (under the car) trans tunnel insulation in a 68 small block stick car?

The trans, Bell-housing, clutch, shifter and support brackets are out for service and going back in soon. The OEM triangular fasteners are in tact. I've bent them back out, but this significantly reduces the space to allow the insulation to fit up into the tunnel. Does the insulation simply need to be bent and man handled? Bending it to the extent I need to get it to fit will cause damage to this new piece. Any in site on proper installation and how to deal with the triangular faster tabs will be greatly appreciated. I do have new fastener tabs I can rivet into the floor if needed.

TX Dave.

[Gene M.]

Re: 68 3/4 speed trans tunnel insulation installation

David, unless you replace the steel pointed sheet metal parts the second bending is going to be shorter than the original. I made new metal pointed securing plates and made the pointed legs a bit longer to give a better secure of the insulation than the originals did. It made for more surface area in contact to keep the insulation from tearing and splitting. Just a suggestion........but it does require getting the interior carpet out of the way to install new rivets.

[Patrick H.]

Re: 68 3/4 speed trans tunnel insulation installation

I've put a couple of these in place, and reattached a couple of originals.
I may have had to tweak it a bit, but not as much that would have to be "bent and man handled." Usually I install one side and then the other, and be prepared for it to want to fall off no matter what. It takes some slow bending of the pointed retainers to get them to hold it in place.

[David M.]

Re: 68 3/4 speed trans tunnel insulation installation

Ok great info. Im not fully understanding the pointed sheet metal fasteners. I have new ones from CC. So do you push the fasteners through the insulation first then try to find the drilled out original rivet holes? Then rivet from the interior side. The cars on a lift about 15 miles away so I cant verify the direction on the rivets from memory. So I guess what Im saying guys is can you spoon feed the installation technique?

TX
Dave

[Patrick H.]

Re: 68 3/4 speed trans tunnel insulation installation

Are the original fasteners still in place? I've personally never removed them or replaced them.

If you have for some reason removed them, then I'd first install the new ones onto the body of the car. The tabs of them then get pointed straight into the transmission tunnel, if that makes sense, and pierce the insulation.
Once through, bend the tabs out to retain the insulation. You will want to use a drift, brass or steel, to tap them flat and retain as much of the insulation as possible.

If you have the old one, set it in place and look at the old mounting holes. Don't install it, as the tabs WILL break off if you use them too often. Not that I'd know...



Thanks to Alan Struck for the photo.

[David M.]

Re: 68 3/4 speed trans tunnel insulation installation

That makes sense. My trouble is the triangular sheet metal tabs which are all present (I have new if needed). With the tabs bent out the insulation is way too big to get into position past the tabs before piercing through. In other words the tabs wont allow flush mounting of the insulation to the floor to accurately pierce the insulation into its final location. From what I demise I need to bend the hell out of the insulation to get it into position before sending it home on the mounting tabs.

Sure wish I could have watch one of these go down the line in 68 to see how the factory did things. I cant imagine the hair pulling/loss in 67 when they were assembling the pre-production cars.

[David M.]

Re: 68 3/4 speed trans tunnel insulation installation

Well to close the loop here there isn't a clean way to install this preformed insulation with the body on the frame even with the trans removed. Mind you this car has the non removable trans cross member. It went in but I had to damage the tail end to get it in. I had to forcefully squeeze it together, you can imagine what happened after that. Then by the time I was done wrestling the trans in, it more or less looked like "sheet" or very similar to the tattered OEM I removed by the time the trans tail shaft bruised it up. What a POS design. That money would have been better spent on beer and dynamat. Id say one would be far better off affixing dynamat to the interior of the floor and not even bother messing with this poorly designed insulation. The rivets that come with the fasteners are not pop rivets. They are old school rivets with a stem and cap. Which need to be hammered in with a rivet machine in order to peen over the stem. The sheet metal fastener tabs and rivets are not doable in a DIY garage IMO. Now if this car had a removable trans cross member this story would be different. I can guarantee you it will have a removable cross member the next time the clutch and trans need to come out. My first tool out of the box will be a plasma cutter going directly at that obnoxious xmember.

[Patrick H.]

Re: 68 3/4 speed trans tunnel insulation installation

I wonder if it depends on the supplier or manufacturer of the insulation?
As I noted previously, I had no such issues with the ones I installed, but it has been a few years since I did one.

[David M.]

Re: 68 3/4 speed trans tunnel insulation installation

Pat,
The part appeared to be of high quality. I got it from Corvette Central. All of the correct contours were there. The installation seems to be the problem. The only way I can see a clean installation is with the body off the frame and/or with a removable cross member. With the cross member out of the way you dont have to thread the trans through that spot. Not to mention the shifter is in the way as well. With a removable xmember damage can be avoided by the trans tail shaft. This mod will also favorably aid in trans installation.

If I did this again I would remove the fixed xmember and install the removable kit. I would then remove the interior drill out all the old tin fasteners. Then locate the correct positions for the fasteners in the insulation and pre-punch them through it. With the tin fasteners affixed or at least pushed through (and maybe not bent) the insulation, I would then put the insulation into position and pop rivet the fasteners and backers all in one motion. Then bend the tabs and be done. I dont see any way of using the OEM style rivets. It could possibly be accomplished with two people. One holding a backer tool on one side of the tunnel then one using a rivet or pneumatic hammer on the under side.

Another option would be to affix it with fender washers. Locate the insulation where you want it. Drill through it and the floor. Then using high grade SS304 washers and good large headed pop rivets....rivet through the washers insulation and the floor simultaneously.

Option 3. Remove all the OEM fasteners so the tunnel is smooth and find an adhesive designed for that environment and glue it in. Large strides have been made in adhesives today. This would be the cleanest method IMO.

Option 4. Dynamat. Though Im not sure the application would be right under the car. I think its designed for sound attenuation in the interior and not as a heat shield by drive train components. You still need to keep the heat off the glass floors IMO.

[Richard G.]

Re: 68 3/4 speed trans tunnel insulation installation

Here is a picture of the factory insulator I purchased in the 80's from GM.
Rick