In cleaning up the frame today I ran across a "thing" that I cannot ID. I've looked in the master parts catalog - to no avail. It is shown circled in yellow in the first picture below, and then in two closer shots.

It is where the #1 crossmember meets the frame and the inside reinforcement. And, it is loose! The one on the passenger's side is a true rivet, but this one is odd. I'm concerned that it is supposed to be a rivet and needs to be tight, so I'd really like to know if any of you have something similar or a true rivet. Since the engine is going to be bit stronger I'm thinking I need to cut that one off and install a G8 bolt.

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My 84 F250 4x4 has it also, its a bolt that holds the steering box plate tight to the bottom. My truck has threads hanging down so its a blind nut setup.

Interestingly, the 91 F150 frame I have has a rivet in that place.

 

Well, ok. Thanks. But in my case it doesn't hold anything tight. It does have things aligned, but mine is easily turned by hand and rattles a little bit. So, I'm thinking I'll use a cutoff wheel on the Dremel and put a bolt in there. At least it would be tight.

 

I didn't check to see if there is a bolt head on the 84 truck. It may very well be a location pin.

 

My other '81 has the same thing but it is tight. No looseness what so ever.

 

looks like you got a bit of a crack there, bud

 

Where? I haven't spotted it and that could change everything. Please point it out.

 

right above the rivet (or is it a real cool shadow)

 

Which rivet? Can you describe the location?

 

She's a Huck bolt Gary, standard aviation fare.

Similar to a rivet, they are pulled up tight and the collar is swaged until the core bolt yields.
They should be tight, if they have worked loose they are no longer doing their job. The factory would have used them where it was easier and faster then a solid rivet or bolt due to head side access.
To remove it, just split the collar off with a cold chisel and punch it out.

A fresh grade 8 bolt with a light interference fit on the shoulder would replace it nicely

 

Na, it's just a small gap between the frame rails, for whatever reason they stopped the weld about half an inch from the end. Possibly they designed it to flex around this area of the junction and that's why it's not welded up as tight as it could all be.

 

Thanks, Brad. If by "shoulder" you mean an unthreaded portion the I understand. But I'm not sure I can find a G8 with that short of a shoulder, although I could run the threads down further on one with a longer shoulder. Anyway, looks like I'll be pulling that out and replacing it.

 

Yep, the unthreaded shoulder of the bolt that carries the shear loads.

If there's no shoulder, then it's a machine screw, but you probably knew that

 

If they ran a complete bead with that weld there'd be no place for rust to start, then what would we do with our weekends? ~Bill

 

Yeah, I'm surprised that given the North American climate and the salted roads, these chassis were not put together with a potting compound between the surfaces, or even better hot gal dipped once assembled.

But where's the fun in that