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Rooncicle

Interior help - fiberglass over hole in tranny tunnel

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PO of my 74 tii stuffed in a dingy e21 carpet that I finally ripped it out to replace with a stock carpet. Quiksteel'd screw holes, removed tar, rust reformer on surface rust, & painted with rustoleum protective enamel. Getting ready to lay down B-quiet mat but I have some concerns.

 

PO put a large gash (3'' at the widest, 6'' long) the driver side tranny tunnel - I'm guessing while doing the 5-speed swap - which was originally hidden by that stock sound deadening piece, and filled in with spray-on insulating foam. The sound deadening was disintegrating from a years of a heater box leak, so I pulled it out and chucked it which maybe I shouldn't have. Decided to remove the foam and fiberglassed the hole, but now I'm wondering if the tranny tunnel gets hot enough that this would be problematic.

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How close to the exhaust pipe is it? other wise I wouldn't think the tranny would not make that much heat I don't think it would ever get hot enough to boil water but that's just a guess. Look at the resin can it should give the max working temp or maybe you'd have to go online but the info should be around. 

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The exhaust pipe isn't close, so that wouldn't be an issue. But I just got off of the phone with a quality body shop - which I should've done before going crazy with the fiberglass - and the guy simply recommended getting a steel plate, forming it to the curvature, and using some jb weld + self-tapping screws. He also recommended that I mark the spot on the sound mat so if I need to access the plate later, it will be easy to find. Easy enough.

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1 hour ago, Rooncicle said:

getting a steel plate, forming it to the curvature, and using some jb weld + self-tapping screws.

I've used this technique to repair rust holes in the floor, but I used wet patch roofing cement on the perimeter of the patch, and fastened it in place with pop rivets.

 

Used in the way proposed above, the JB weld will crack due to torsional loads on the body because it isn't flexible like the roofing cement is.  And unless you're planning the patch as an access, pop rivets will hold better than sheet metal screws.   

 

mike

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11 minutes ago, mike said:

I've used this technique to repair rust holes in the floor, but I used wet patch roofing cement on the perimeter of the patch, and fastened it in place with pop rivets.

 

Used in the way proposed above, the JB weld will crack due to torsional loads on the body because it isn't flexible like the roofing cement is.  And unless you're planning the patch as an access, pop rivets will hold better than sheet metal screws.   

 

mike

 

Thanks, Mike - I'll go that route

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I wouldn't use JB weld for that.I would use something from the RV world called Eternabond.  You can get in a double sided version.  It's pressure activated, and self healing. 

 

Although if it were me, I would weld in new steel.

 

Jose

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@DaHose @mike

 

related note: after stripping the inside of the tar mat to hunt down any rust that might be lurking, I painted the floor, space under the back seat, and tranny tunnel with rustoleum protective enamel. The rustoleum site says this paint can tolerate up to 200F. There shouldn’t be any problems due to heat from the exhaust, right? 

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If the flooring metal is reaching 200°F then the original bitumen sound deadener would have become a sticky mess.

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@jimk I thought I already responded, but I guess not. When you say floor, are you including the tunnel? Being so overly cautious that a 2-day job turned into a 2-week job. I don't want to finish making the interior pretty just to have a paint crisis on the freeway.

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The factory floor sound dampening material next to the tunnel would have shown melting.

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@DaHose I just got the roofing cement today and it says allow 30-60 days to cure before applying the reflective coating... how long did you allow the stuff to cure when you used it?

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