Tech- Fabricating frame-to-body mounts, part 1

I don't expect everybody to run out to their driveway today and copy this tech piece, it's fairly involved and requires some expensive tools. But I want to present it so you know what's possible and how it's done. Just because you don't do heart surgery doesn't mean it's not interesting, right? This is a typical cab mount on a pickup truck. Most classic cars that are body-on-frame construction are similar. The frame is on the right, and the hoop-like mount is welded to it. A bolt passes through a big washer, a rubber/steel biscuit assembly, and into the floor of the body above.

Here is what they look like after time and corrosion has taken their toll. Pretty gruesome, right? You can see the hoop-mount is half rusted away. The biscuit assembly is not really resting on anything. The floor pan looks bad but is pretty solid. I think I can save this.

Cranking on the bolt produced some promising turns, but after a few, it got completely loose and would not come out: something was broken. At the factory, these bolts are assembled up into a threaded plate. After rust fuses the bolt to the plate, the bolt will break, or the plate will just spin. The car manufacturer does not care that you can't get these out; they will, however, be happy to sell you another car.

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I had to cut the bolt head off with an acetylene torch. The biscuit came off, but the rest of the bolt was still stuck on the threaded plate above the floor pan. The threaded plate actually rests in a pocket between 2 layers of steel floor, so you can't just lift up the carpet and pull it out, it's in there good. Now what?

More destruction. I took a big holesaw and cut an access hole right through the floor from inside the vehicle over the mounting area. It's big, like 2-1/2". From there, I could pull the plate and bolt shaft out. Here you can see the rusty devil itself. It looks like I made more work, but sometimes it takes work. After I'm done, I'll weld or screw a patch over the hole, seal it, and it will be the best part of the floor. It actually does look like heart surgery now.

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I shop-vac'd a ton of junk out of the pocket area. It's not owner negligence or anything, cars have lots of pockets like this that collect road junk and deteriorate. Rust happens.

Here are the remnants of the biscuit assembly and the rusty parts that fell off. Boooooooo! I ordered replacement items for all of this. In part 2, I will fabricate a new frame hoop-mount out of steel plate, and weld it onto the frame. I'll assemble the mount parts and restore the whole area. A challenging and fun project. Thanks and stay tuned.