Is welding two truck frames together an awful idea?

[dieselcrawler]

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

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'.

 

[kenmac]

I have no idea what they say today. But back in the 70's I worked in a truck shop. All truck frames were stamped ''do not weld or cut on the truck frame''
We had to drill holes and bolt the things we added to the truck frames

 

[Tractor Seabee]

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

 

[boomer1025]

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.

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

 

[sandfs]

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.

 

[Arc weld]

Truck frames are lengthened and shortened everyday. Make the cuts at 45 deg's. and use the correct filler metal and procedure. Not a job for someone inexperienced.

 

[truckdiagnostics]

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.

 

[drizler]

Can you simply chop it behind the cab where the usual 2 frames meet? Die grind out the piece of frame and then take a piece of structural steel that will sleeve fit . I know you can with GM 1500 frames. Drill some plug weld holes where the front frame laps over the inserted pieces and drive it in as far as it will go, about a foot then weld , fish plate . On mine at least that front frame is made of regular heavy steel that welds fine. It’s that rear section that rolls up like burned tissue paper. I just cut the lower 3/4 off and left the top rail as a templet for mounting alignment. It looks like a real hack job from the side but under that cosmetic is 1/4” filleted channel. Wire wheel , grind prime paint with PoR15 and undercoat. It will far outlast the truck.
Or use that method to make a long doubler to mate the OEM rear to the front. I did my 2000 with a plum bob and tape measure 4 years ago the first way using a piece of old structural steel that fit like a glove . The alignment guy told me he’s seen far worse right from GM . It’s primitive under there so making your own is incredibly easy compared to other things. Make your own cross members too from heavy pipe or boxed tubing. Easy welding too with no bed on . All your hangers will bolt right on or weld easily as needed.
Take your time and recondition , wire wheel, POR , undercoat everything including the underside of the box or bed. It’s a good time to address new brake lines fuel lines, gas tank straps even new fuel pump ect as It’s so easy to get at everything well standing right over it. Make it a project drink beer and have fun while taking all the time to do it right and above all ONCE. You’ll likely never have to get under there again.

 

[searcyfarms]

i will add that my neighbor worked 37 years at Ford in KC in their large truck division, he also has worked at another LARGE truck company here in KC after retiring from ford and is still working on them, everything from concrete trucks, fire trucks, semis, dump trucks, trailers, buses, they weld frames all the time and some heavy trucks are even double frames, when they roll over and twist frames they have to be cut out and replaced, there is plenty of welding done on them AND some are redrilled for spring hangars etc after doing the welding etc.....so i dont think you have anything to worry about welding and then sandwiching support on either or both sides to add structural integrity where the break/cut was, if you are anything like most of us moonlight fabricators, it will likely be over engineers because we all know if two bolts are good three is better, two welds are good three is better, lol!!!!

 

[4570Man]

While I feel like I could probably weld it I’d probably try to get the professional welder from the metal shop to come over and do it.