Is welding two truck frames together an awful idea? (2024)

aczlan said:

Yep, you want something like this for your frame cuts:
View attachment 586079
Then weld it and weld a gusset over it that has rounded corners.

Aaron Z

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That type of splice is how I plan to join the front and rear halfs of the truck I'm building, a crew cab with an extended cab rear section added on, using the rear 2/3 of one frame, and front half of the other, with the splice going under the cab, just behind the trans cross member. Fish plates inside the rails, and likely an additional cross member, to add another 'rung' to the 'ladder'.

When they add to the rails of the Chev P-30 for the long motor homes the ones I have seen (owned a 41'er) are bolted with fish plates in and out. Attaching the tag axle was also all bolted assembly. Saw no welding was done. I would think a mag base drill would be the proper means of drilling the frame rails.

I do know that trailers sold for highway use are required to be welded by AWS certified welders and are inspected including spot check of weld by a certified inspector. DOT regulations cover that work. I learned that as a QC inspector in modular building manufacturing plants. I had to collect the DOT inspection reports on each unit for the record. All manufactured trailers have to have that cert to be licensed.

Ron

4570Man said:

I’ve got a Ford 700 that used to be a U-haul box truck. Someone else attempted to convert it to a ramp truck. I now have a GMC topkick lopro that used to be a Penske truck that I bought because the hood and seat that I needed is worth nearly half what I paid. The Allison and Cat from it might go in another project. I was thinking about cutting both trucks in half about the back of the cab and welding the Ford back on the Kodiak rear section. That’s assuming the frame rails are pretty close to the same.

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Here you go, click on the link and scroll down to Item 7.
Body Builder Manuals | Mack Trucks

I would imagine that most 'do not weld, cut bolt, grind, look at or alter' statements by manufacturers is more a matter of liability than practicality or reality. Makes perfect legal sense, but it would be rare that the metals are so exotic that they cannot be worked with in some safe fashion. As in the post above Mack says 'if you are going to screw with it, let us guide you through it'. That's good on them.

I, personally, would assume that if I alter a vehicle in some way that I accept the liability for anything that occurs as a result of that modification but i suppose in todays litigious society folks are going to want to sue the manufacturer no matter what.

Mag drills are nice but for drilling a frame, this is the way to go. Zip Cut don't remember why you where adding frame or cutting/putting together. The body builder info above from Mack is good info. On a straight frame if we where going to increase wheel base we would do a slid and add frame on the end.

With a frame drill adding a liner was easy. On inside i think it looks better. If you can go on the outside, you can have the machine shop punch the holes before they put it in the break, making it easier for drilling. When fish plating on a frame that is not real wide getting much of a fish plate in there and staying out of welding in the radius of the frame rail is hard. If I remember correctly they do not or it is not recommended to weld in the frame rail radius.

Whenever we had to extend wheel base on non straight frame vehicles we cut the frame at an angle welded, then either added liner or support on outside bolted.