Shortening a Frame
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Joined: Sep 2003
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Shortening a Frame
I recently bought a 1987 F 150 4x4 4.9 from my cousin. The bed is completely gone, now bondo can save her now. but everything else is fine. I also have another 87 F 150 2x4 4.9 that just died. the difference is my 2x4 has a perfect 6 foot bed on it, but the 4x4 had the 8 foot bed. (i personally like the way a short bed looks compared to the long bed) anyhow, in order for me to put this bed on i need to shorten the frame, i have all the part i need, from my old truck. ie. drive shaft. my question is how hard is it to shorten the frame i know its got to be perfect. any tips or does anyone know of how much a job like this might cost?
Senior User
Joined: Jan 2004
Posts: 161
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From: The KeyStone State
Take a good look at the frames, IIRC the 4X4 and 4X2 trucks have the same frames.
I'm not a fan of welded frames.
You WILL be better off just swapping over the necessary components to the 4X2's frame. I'm sure it'll cost less than welding.
Technically, you're truck will need a reconstructed title either way.
Shortening the frame can be a liability.
Post Fiend
Joined: Oct 2003
Posts: 6,214
Likes: 13
From: New Jersey
yes, shortening or lengthening the frame can be a liability, however it can be done.
What you do is cut the frame where its straight, so you can line the two pieces up properly. Its much easier to do this with the body, axles, and everything else off.
Once you make your four cuts, you have to insert a slightly smaller "C" channel on the inside of the frame on both sides, so the frame just isn't butt welded together. It should be tight enough that it will stay without welding, but not impossible to get in there. Clamp it in tight, and MIG or TIG weld the entire perimeter of the inner "C" channel as well as any plug welds you want to do.
Lengthening is the same, except you're inserting two pieces of "C" channel same size as the frame to lengthen it, and two slightly smaller like above for strenght.
I lengthed an 81 crewcab about 6', and put a large toolbox the size of the bed on top of the section, with a door on each side.
What you do is cut the frame where its straight, so you can line the two pieces up properly. Its much easier to do this with the body, axles, and everything else off.
Once you make your four cuts, you have to insert a slightly smaller "C" channel on the inside of the frame on both sides, so the frame just isn't butt welded together. It should be tight enough that it will stay without welding, but not impossible to get in there. Clamp it in tight, and MIG or TIG weld the entire perimeter of the inner "C" channel as well as any plug welds you want to do.
Lengthening is the same, except you're inserting two pieces of "C" channel same size as the frame to lengthen it, and two slightly smaller like above for strenght.
I lengthed an 81 crewcab about 6', and put a large toolbox the size of the bed on top of the section, with a door on each side.
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