Welding on a commercial truck frame ????

dmw56 · Nov 10, 2008

A buddy of mine that owns a couple commercial trucks to haul gravel asked me about welding a bracket on for a hydraulic pump. I asked if it was a hardened frame because most I've seen say right on them "hardened frame DO NOT Weld".

I don't know exactly why, but my better judement says they put that on there for a reason and not to do it. There may be even DOT regulations about it. Is it because it will take the temper out and create a weak spot where the weld is? I'd like to give him a reason why it shouldn't be done other than "because it says not to".

maddog · Nov 10, 2008

I dont know about the hardened frame, but I have a shop neighbor that does large structurial steel stuff and used to work in a shop that did truck frame repair and modifications. He was hanging out and discussing the frame I am building for my Fiat. He said they would never weld verticaly on a frame, only horizontally.

Thats all I can tell you, hope it helps.

Bonehead · Nov 10, 2008

The vertical/ horizontal thing was the first thing I was going to say. But there is more, , alot of trucks have a tempered frame. You can take the temper out and cause it to crack with heat. The old ones were no problem, but you have to watch some of the newer ones. If it has holes, build brackets to the holes and bolt them in.

dogpatch1 · Nov 10, 2008

do you kno if its a workhorse chassis? i had to get certified in workhorse do to the fact that our main store works on travel/motorhomes. we are not even aloud to weld horizontally on the chassis. or drill holes larger than specified and they tell us where also. in my workhorse manual it states that all chassis made after 1991 are hardened. but i dont know if this is the same as your commercial chassis. its a pain when installing exhaust brakes or air tanks. also is it a p.t.o style hydraulic pump? is their anyway to mount them to one of the crossovers?

dmw56 · Nov 10, 2008

Bonehead said:
The vertical/ horizontal thing was the first thing I was going to say. But there is more, , alot of trucks have a tempered frame. You can take the temper out and cause it to crack with heat. The old ones were no problem, but you have to watch some of the newer ones. If it has holes, build brakets to the holes and bolt them in.

dogpatch1 said:
do you kno if its a workhorse chassis? i had to get certified in workhorse do to the fact that our main store works on travel/motorhomes. we are not even aloud to weld horizontally on the chassis. or drill holes larger than specified and they tell us where also. in my workhorse manual it states that all chassis made after 1991 are hardened. but i dont know if this is the same as your commercial chassis. its a pain when installing exhaust brakes or air tanks. also is it a p.t.o style hydraulic pump? is their anyway to mount them to one of the crossovers?

Yes, that's what I thought. I don't know if it's a workhorse frame but it is a pto driven hydraulic pump. I told him it is best to make a bracket and bolt it to the frame or make a "crossover" which is bolted to the frame and weld/bolt the pump to that. I just don't like the idea welding a tempered frame.

Thanks Guys.

hillbilly4008 · Nov 12, 2008

I gotta agree with the guys on this one. Make sure he bolts his stuff on. I do 99% of my work on commercial trucks, and the only time i ever weld to the frame is when im doing the pivot point if its a rollback or a dump body. All tanks, cylinders, bodylocks, hoists, booms, hitches are bolted on. Most of the time its real work to drill holes through truck frames, especially double frames, but its the right way to do it.
We lengthen and shorten truck frames by welding em back togeather, but thats a whole other subject.

Unkl Ian · Nov 12, 2008

A Tempered frame is similar to a spring. It can flex repeatedly without breaking.

By welding, the heat destroys the Temper around the weld area,
creating a soft spot. So that area can work harden and crack.

Same reason you don't heat coil springs to lower a car.
There is a very good chance they will work harden and break.

ascenttm · Dec 21, 2008

In Michigan you can't weld on a frame unless you are certified, at least that's what the DOT says. I know of a guy who welds lots of trucks and he only uses low hydogen rods. Like everything I see in front of the axles is bolted.

marco · Jan 9, 2009

HillbillyS is spot on.I did it for years at Janell Truck Body in RI.Those trucks were delivied up and down the east coast and insp by the DOT before leaving

Huryinhoosier · Jan 9, 2009

Unkl Ian is correct....I worked for Freightliner for years we never welded on anything other than the aprons.

southerniron · Apr 18, 2009

build a bracket and bolt it to the frame ..i used to work for a fab shop that mounted cranes and piggy back fork lifts on tractors and trailers ...and we werent even allowed to tack on a frame .. the **** will crack !! seen it happen ! you can get away with welding behind the axles like the last 1 foot of the frame .. we did with auxilary out riggers . all of the sub frames and fish plates would be bolted .. and that is a pain in the ass ..100+ 5/8" bolts

deiselrodder · Aug 16, 2011

Its against DOT regs to place an unauthorized weld on a commercial truck frame.

dmw56 · Aug 16, 2011

deiselrodder said:
Its against DOT regs to place an unauthorized weld on a commercial truck frame.

That's what I figured.

Crossfire · Aug 17, 2011

Frame welding

We have a fleet of 38 trucks,all with pto driven pumps. All are bolted on units.The only time I weld on a frame is if I find a crack and then just weld and double plate with bolts.The best unit I have is a Heil unit that has the pump and tank as one unit with shaft driven pump on front of tank.Holds about 30 gallons of fluid and controls packer units and dump bed cylinders.It is mounted on 2 cross members bolted to the frame.[

Torch · Dec 2, 2011

everything you need to know about modding a truck frame
http://ratrodsrule.com/forum/showthread.php?p=251020&posted=1#post251020

found it on the net and saved it. started it as it's own thread so it's easier to find and point to.
If someone wants to edit it and make it a sticky go for it.

meteorman · Jun 1, 2013

Help. I am now wondering if the 1978 dodge m400 chassis used hardened steel or not. I stripped it down and didn't see any warnings on it not to weld. How can I tell if it was hardened? I think I saw that they started using hardened steel in the 90's. anybody know?

Welding on a commercial truck frame ????

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