Is welding two truck frames together an awful idea?

[4570Man]

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.

 

[Stimw]

You don't weld the frames back together!
Truck frames are hardened and welding will ruin the temper and crack/break.
You have a good fabrication shop make/break channels that fit inside the frame rails and you drill and bolt back together.
It's done all the time in truck shops installing additional equipment.
I had a Boom Truck that was a Ford Dump Truck that was cut and extended and a flatbed added with a 21' boom for delivering concrete block. It would haul 10 cubes. (cube is 4' X 4')

 

[RNeumann]

Typically it’s more than a butt weld and off you go. You will typically need some gusseting and a lot of measuring and jigging. I’ve seen some that are nice and some that are scary. Take your time, do the research and you will get good results.

What are you trying to “make”

 

[4570Man]

Typically it’s more than a butt weld and off you go. You will typically need some gusseting and a lot of measuring and jigging. I’ve seen some that are nice and some that are scary. Take your time, do the research and you will get good results.

What are you trying to “make”

I’m trying to cut up one perfectly good box truck and weld it together to make another box truck. Brilliant plan right? The alternative plan is to put my busted hood back on it, but my straight bench seat back in it which will work in this truck since it doesn’t need a cutout for the gear shift and not take the $500 worth of tires and put on my HD and not put the cat in my International truck.

 

[RNeumann]

Just a box truck!?!? U will be fine.....just keep it under 60mph. That, of course is sarcasm. In all seriousness frames are cut every day- RVs, ambulances etc. What little I’ve done with 4x4s on the frame I know you don’t want square corners if it can be avoided. Use ovals instead of rectangles for gussets and probably a Z or angle cut instead of a straight cut on the rails. But like I said before, do the research and take your time.

 

[aczlan]

Just a box truck!?!? U will be fine.....just keep it under 60mph. That, of course is sarcasm. In all seriousness frames are cut every day- RVs, ambulances etc. What little I’ve done with 4x4s on the frame I know you don’t want square corners if it can be avoided. Use ovals instead of rectangles for gussets and probably a Z or angle cut instead of a straight cut on the rails. But like I said before, do the research and take your time.

Yep, you want something like this for your frame cuts:

Then weld it and weld a gusset over it that has rounded corners.

Aaron Z

 

[truckdiagnostics]

What others have said. Cut it at an angle weld it together. If you have enough space on the inside frame rail, consider having a liner bent up that fits inside the frame rail, then bolt it. Not a real fan of fish plating, seen it done, on a box truck fish plating should work, but much rather see double frame. If you plan where you cut it don't see an issue. The problem you might run into is on some of the medium duty trucks the frame rails are not straight so it becomes more difficult. Good luck its do able.

 

[rangerfredbob]

I've been to a shop that did frame modification on heavy trucks, had at least 2 in the shop when I was there... they cut the frame as shown above then "fish plated" over the joint, I was only there for 2 days working on a street sweeper so don't know everything about it but the trucks they were working on were getting vacuum outfits like a Vactor truck...

 

[Paystar]

Back in the old days we welded class 8 truck frames to lengthen them. Just fish plated them inside and outside the rail where they were joined. These were on dump trucks that pulled pony trailers at grossing 140,000 pounds. I never had any issues with them after being welded.

But we normally tried to do it an an area of least load and stress.

 

[Alan W.]

Back in the old days we welded class 8 truck frames to lengthen them. Just fish plated them inside and outside the rail where they were joined. These were on dump trucks that pulled pony trailers at grossing 140,000 pounds. I never had any issues with them after being welded.

But we normally tried to do it an an area of least load and stress.

In my younger days I worked at Cherokee and Ive shortened and lengthened quite a few trucks for a rollback bed. Some were for the coal mines, triple framed behemoths. Staggered the joints and plated them. Never had a return and there is no telling how much those offroad trucks hauled.