'68 300 Stub Frame Repair

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mgm1986

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Been reading through previous threads about repairing or replacing the stub frame. I knew when I bought the car there was a rust issue in the stub frame, under the drivers door (Green arrow in first pic). The rest of the stub frame seems very solid but this area looks like it was maybe hit or improperly jacked up at some point as it is dented in on the bottom (where the rust is).

My plan is to repair this without removing the stub frame but I would like your input so I can make the best decision. It seems a good welder would be able to fix this by cutting out the bottom rust and welding in new metal.

Any thoughts or suggestions from those who have tackled this before?
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It's been a while since I've looked at my cars in that area, but it seems like the sections are made from two C-sections welded together? Might be easy to weld and all of that, PROVIDED you use the correct gauge/thickness and metal-specification of metal to weld back into the item. THEN metal-prep and paint with rust-preventative paint and apply a waxy corrosion-preventative coating for best long-term results.

Just some thoughts,
CBODY67
 
As a demo guy I can attest that it's real easy to do on a hoist. Lift car up. Cut rust area out no need to brace or anything. Cut it out, then trave onto some 1/8" flat steel and weld it in then cover with por-15. Real easy place to repair.
 
Cool, sounds like this could be tackled without removing the stub frame from the car assuming this is indeed the only problem area.

So the proper gauge steel is 1/8"?
 
Some may argue on the size.(the purists) but I've patched dozens with 1/8" you won't need to drop stub. Get up on lift and cut it out as nice as you can then trace it and the spots on the side of the rail do them the best you can, in the derby world we cut entire sections out and weld in 1/4" and make it look stock. And 1/8" is much easier to form and plenty strong to give you the support you need for a stub frame and slightly stronger than original anyway. If you can sand blast the areas with it in the car also it will show you more problem areas because where there is some. There will be more near by. Small blaster will work without getting into everything and it will.make welding in much easier as well with clean metal. Good luck and post pics as you can and we can help with any further questions!
 
mgm1986 said:
Been reading through previous threads about repairing or replacing the stub frame. I knew when I bought the car there was a rust issue in the stub frame, under the drivers door (Green arrow in first pic). The rest of the stub frame seems very solid but this area looks like it was maybe hit or improperly jacked up at some point as it is dented in on the bottom (where the rust is).

My plan is to repair this without removing the stub frame but I would like your input so I can make the best decision. It seems a good welder would be able to fix this by cutting out the bottom rust and welding in new metal.

Any thoughts or suggestions from those who have tackled this before?View attachment 627625View attachment 627626View attachment 627627View attachment 627628View attachment 627629View attachment 627630View attachment 627631
Click to expand...
My theory of why it rusts on the driver side is the position of the battery. The battery tray drains down into the frame rail.
 
If you've ever cut one of these stubs open to investigate they are very thin compared to even the 74-78 stubs or any other make or model from gm or ford of the same Era. Chrysler is thin in this style of stub. the imperials are different of this Era so that's a different discussion but as far as why these rust so bad in the rear legs it's lack of material thickness and they have several holes that capture road grime and moisture with no way to drain and it just eats away at them and being so thin it doesn't take long to do damage
 
It does seem like thin metal for a frame. And it definitely captured a bunch of stuff through the years. It was actually insulated really well though thanks to the mouse that made a nest up there and apparently never found his way out!

The battery tray theory is a good one. Oddly, the tray actually looks to be in good shape but I have no idea if it was ever replaced.

I’ll get things cleaned up and inspect the rest of the frame before deciding next steps but I like the idea that this could be fixed without removing the stub frame.
 
There is a company in Rhode Island that made stub frame patch sections they don't list C Body's on their website. They may be able to make them for you. autorust.com
 
mgm1986 said:
It does seem like thin metal for a frame. And it definitely captured a bunch of stuff through the years. It was actually insulated really well though thanks to the mouse that made a nest up there and apparently never found his way out!

The battery tray theory is a good one. Oddly, the tray actually looks to be in good shape but I have no idea if it was ever replaced.

I’ll get things cleaned up and inspect the rest of the frame before deciding next steps but I like the idea that this could be fixed without removing the stub frame.
Click to expand...
Thanks for this info Owen. I am looking at buying a 1971 Plymouth Gran Fury in need of stub frame repair and I am more optimistic after reading what you say.
 
Definitely, your the only one to judge what is "too much" there comes a time where it's easier to just start over with new stub but these specific style stubs are simple as can be to repair.
 
I have a great condition 68 stub frame from a Fury if you’re interested. PM me if you want to talk more and I can get you pictures, etc.
 
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