As most everybody here who has more than a couple of hours welding experience, knows, a proper weld will be as strong or stronger than the parent metal.
The heat treated big truck frames do have stickers saying not to weld to them and for good reason.
They can be welded to, but to maintain the original strength, would require heat treatment beyond the abilities of most welding shops.
Not because they cannot heat treat, its just that they don't have a way to get the frame in the kiln.
Regular truck frames are tough, but not hardened. A well done weld should not be any problem at all.
The main way a proper weld could fail is to crack just past the weld. You see this a lot especially on thin pieces of steel. The weld holds, but the parent metal cracks right next to it.
This is caused because an arc weld dumps a lot of heat into the metal real fast. And then, in a thin piece, the heat goes away quickly.
This caused a stress riser because the metal changes to two different hardnesses in a very narrow area.
In one place the metal is fairly soft having been annealed, and right next to it, it is really hard having been hardened by the high heat and quick quench.
It breaks right at that border.
Thats why when welding thin pieces, you often need to reheat the weld and the area around it with a torch to let the transition zone spread out.
Also, a BIG gotcha, is that a lot of the newer truck have plastic fuel lines.
In 1989, when I had my brand new 3/4 ton truck cut in half and shortened to SWB specs, it all went great. I wound up with a SWB 3/4 ton truck.
As I took it out on it maiden voyage to the farm, I switched to the back tank just as I turned off the highway.
When I pulled up to the gate, A HUGE cloud of white smoke enveloped me. I shut it down and jumped out.
Turned out a tiny piece of weld spatter had bounced all the way across the underside of the truck and melted its self into the back fuel line.
When I turned on the back tank, the pressure caused a stream of gas to shoot across under the truck and hit the cat dead on........
Lots of fun.
I carefully switched back to the front tank, eased into the yard, and went looking for a splice kit.
So watch the splatter.
J.
The heat treated big truck frames do have stickers saying not to weld to them and for good reason.
They can be welded to, but to maintain the original strength, would require heat treatment beyond the abilities of most welding shops.
Not because they cannot heat treat, its just that they don't have a way to get the frame in the kiln.
Regular truck frames are tough, but not hardened. A well done weld should not be any problem at all.
The main way a proper weld could fail is to crack just past the weld. You see this a lot especially on thin pieces of steel. The weld holds, but the parent metal cracks right next to it.
This is caused because an arc weld dumps a lot of heat into the metal real fast. And then, in a thin piece, the heat goes away quickly.
This caused a stress riser because the metal changes to two different hardnesses in a very narrow area.
In one place the metal is fairly soft having been annealed, and right next to it, it is really hard having been hardened by the high heat and quick quench.
It breaks right at that border.
Thats why when welding thin pieces, you often need to reheat the weld and the area around it with a torch to let the transition zone spread out.
Also, a BIG gotcha, is that a lot of the newer truck have plastic fuel lines.
In 1989, when I had my brand new 3/4 ton truck cut in half and shortened to SWB specs, it all went great. I wound up with a SWB 3/4 ton truck.
As I took it out on it maiden voyage to the farm, I switched to the back tank just as I turned off the highway.
When I pulled up to the gate, A HUGE cloud of white smoke enveloped me. I shut it down and jumped out.
Turned out a tiny piece of weld spatter had bounced all the way across the underside of the truck and melted its self into the back fuel line.
When I turned on the back tank, the pressure caused a stream of gas to shoot across under the truck and hit the cat dead on........
Lots of fun.
I carefully switched back to the front tank, eased into the yard, and went looking for a splice kit.
So watch the splatter.
J.
Please point out where I am wrong. Whats your point? Point out where I'm talking about what I don't know then get back to me. OR keep running you mouth just because you feel you need to.
Just enjoying the melee! 
