While stripping my frame yesterday I discovered that I had a crack right under the front cab mount. It's a pretty good crack that runs from the middle of the top of the frame down to the large whole where I believe the brake pivot bolt attached to the frame. If it wasn't for the cab mount being bolted on both sides of the crack it would have just broken off (scary). Upon further inspection of the other side I realized that it had cracked also and the PO (probably years ago on some farm) welded what looks like a piece of another smaller frame inside the frame rail. It looks really tacky but it seems to be working. I did a little internet research to see how to fix the crack and from what I read I should drill a hole at both ends of the crack to stop it from spreading and then grind a 'V' into the crack and weld and grind it flat.

Is this the best method for repairing a crack in these old trucks?? Also should I be welding some sort of patch on it to reinforce it since it will be right in the front of the cab where most of the weight would settle?? If anyone has repaired this I would be very interested to know what and how you repaired your cracked frames. I'm keeping my fingers crossed that I don't find any more.

Thanks, Rodney

 

weld it then either box it or fish plate it . my cousins 53 has the same issue . he was planning on boxing the frame anyway so we made sure the frame was square , welded away, then boxed it up .

 

Rodney, didn't you decide to install the mustang ll ? you have to box anyway ,right?
Why not just extend the boxing plate like 55f350 mentioned? I would level the frame ,and carefully inspect those cab-struts for sagging. I am no professional weldor, but the method you described..drilling each end of the crack to stop spreading,then grinding and filling ,..has been used along time.Good Luck!
Double check those front cab mount struts for sagging before welding.

 

If it was mine I would do what you said and then fish plate it. I use to work for a company that built big utility trucks, as you can guess these trucks took a beatting.
If a truck came back because of a crack, like the one you are describing, we drilled
holes at each end of the crack, ground a v notch out, then welded it up. After that we would weld a fish plate on. For one ton trucks we used quarter inch plate, for the great big trucks we used half inch plate. Now this may overkill for your project, I hope this information helps you out. Oh buy the way we never had a truck to come back wear we made this repair.

 

Thanks for the responses. Yes, I will be boxing for the MII install. I guess it would be a good idea to box the entire thing (I was tossing around the idea anyway). Also, what exactly is a "fish plate"?

 

Hi Rodney
Looks as if you have the correct information on
your frame, The fish plate is just extra, the weld
should be stronger than any part of the frame
Take care

 

Hey lowtrkn2k; A fish plate is a flat piece of metal that extends passed your weld in both directions. The fish plate needs to be a little thicker than your frame, and it needs to extend at least 10 inch in both direction. the fish is shaped like a dimond, and needs to be welded all the way around. Your plate will look like a baseball dimond.
Dont just use a retangle piece of metal. I hope this helps you. If it were mine I would use quater inch plate. Even with boxing your frame you should still fish plate over your weld. good luck!

 

Got it. Thanks again I'll do that.

 

Good luck on your project, keep us up to date on it. Ive got a 60 one ton duely I plan on starting this spring. It will go all the way to the frame. I hope to get some pics on the forum soon.

 

Ground it out and welded it up:

 

Heres a picture of the "fish plate" that I used when I lengthened my frame.

One thing that I was told when welding fish plates on, you do NOT want to weld the corners of the plates. This will cause stress points that can allow new cracks to form.. so you want to leave about 3/8 to 1/2 inch unwelded each side of the corner.