Need opinions: Frame repair on GMT400

[GM Guy]

hey all,

I am looking at a project pickup. white 6.5L 5spd, 4wd this time. IDK what I am going to do with it if I buy it.

if I fix it up some to use as an on-road pickup, I got a problem.

it looks as if the cutting torch was a removal tool for the flatbed or gooseneck plate, and its left with this:


has anyone here welded on a GMt400 frame? I know on our Semi trucks, they seem pretty concerned about welding on frames, I assume due to it being a higher carbon content? are these frames pretty forgiving as far as patching, welding, etc?

I was thinking of getting a piece from my K2500LD junker, but am concerned about frame thickness. they are different in thickness, correct?

as far as strength, how weak would this be even after being repaired? I may be putting a B&W turnover ball on to add some strength in the area.

Finally, if I ever want to find a donor frame, I should be OK with one from a automatic gasser, correct? as long as its a K2500HD RCLB? Is there a way to tell with the plastic label on the right side towards the front under the cab? I think its a 3 letter code.

any input appreciated, thanks!

 

[GM Guy]

more problems, looks at this pic.



pretty sure the front bed mounts have been hacked off too.


I guess those can be welded on too, couldnt a guy cut these on a flat smooth line, and cut at the same line on a junker, then weld on and fishplate it on both sides to brace it?

some peoples kids....

 

[Will L.]

For the bed mounts, yeah cut straight and two fishplates, welded.


For the top flange, when people would bring me that into my truck equipment shop, i would not even touch it. Liability through the roof. The problem is the frame is trying to flex upward right where the missing part is. Heavy load, rough terrain, or a wreck are going to stress the area.

If it were my truck however I would: cut a staight line along the top. Cut outward 45* front and rear so it is missing a parallelogram. Beveled edges so it is welded with 100% penetration. Flapper wheel down to flush. Inside and outside gloves (c bent mild steel the same thickness of the frame). 6" beyond the repaired area in both directions. Using grade 5 bolts, flat washers, mechanical locknuts to vice the frame inbetween the two gloves.

The shock mounts, line mounts, and all th riveted goodies in the way need to be modified to fit the new inside glove. Bolt through any original holes in frame, Normally 4 bolts on each side in a trapezoid pattern is best.

 

[swinters]

I've welded a bunch of these and they're not a big problem. The key is plating to move the stress away from the weld. On semi trucks you're usually dealing with alloys and it's a lot trickier. There's a really good Army manual on repair of frames that I have in digits (.pdf) but am not sure how to post it or whether that's even allowed. You could do a search for TB 9-2510-242-40 and probably come up with a download. Should tell you everything you need to know.

 

[swinters]

For the bed mounts, yeah cut straight and two fishplates, welded.


For the top flange, when people would bring me that into my truck equipment shop, i would not even touch it. Liability through the roof. The problem is the frame is trying to flex upward right where the missing part is. Heavy load, rough terrain, or a wreck are going to stress the area.

If it were my truck however I would: cut a staight line along the top. Cut outward 45* front and rear so it is missing a parallelogram. Beveled edges so it is welded with 100% penetration. Flapper wheel down to flush. Inside and outside gloves (c bent mild steel the same thickness of the frame). 6" beyond the repaired area in both directions. Using grade 5 bolts, flat washers, mechanical locknuts to vice the frame inbetween the two gloves.

The shock mounts, line mounts, and all th riveted goodies in the way need to be modified to fit the new inside glove. Bolt through any original holes in frame, Normally 4 bolts on each side in a trapezoid pattern is best.

Sounds like you done this before! One thing a old-timer showed me when I first started working in truck shops is when you use bolts on frames, drill the hole and then tap it, run the bolt in and then put a locknut on it. Best method I've found to get the tight fit that you need on a frame bolt.

 

[tanman_2006]

I'd do a frame swap using the LD frame worst case scenario. For a gooseneck pulling truck you should be fine, tongue weight seems to be the killer of 1500's...... Will's idea sounds solid though.

 

[gmctrucksrock]

If it was me I would weld patch in and then cut an piece longer than patch out of another frame and add it to spot over lapping same roll in frame corners where ever there is a rivet on base frame make holes bigger on over lapping piece and lay on top also keep two to three inches of each side so the L shape is given it strength, I'm in the process of doing same thing on under side of frame of a wrecker from rear spring hanger to forward cab mount, My cousin taco-ed the frame of the first wrecker by tieing two trucks bumper to bumper which then frame folded up right between cab and wrecker bed, not to say that it couldn't be done again but the under side of frame will be doubled, I'm going to plug weld it in three spots the bolt it about 6 - 8 different places to allow it to flex and not break welds

 

[WarWagon]

:rant: Frames are going for the cost of scrap metal at junkyards. Why would you get one you have to majorly F with and then deal with the liability? Towing is hard on frames requiring all their strength. A busted frame on a company pickup is not repairable solely for liability reasons. You are not indestructible yourself and living through a near fatal accident takes years of recovery and maybe you have full use of all your limbs again if you are really lucky.

Any wreck is bad enough risking all you own. One after a repaired frame gives up has any other parties involved coming after you for everything they can get. I have seen businesses go under after a low rider job breaks on the freeway at freeway speed...

In AZ insurance companies do not have to pay out for negligence like not wearing a seat belt. Not lowered my rates any, but...

 

[Will L.]

Sounds like you done this before! One thing a old-timer showed me when I first started working in truck shops is when you use bolts on frames, drill the hole and then tap it, run the bolt in and then put a locknut on it. Best method I've found to get the tight fit that you need on a frame bolt.

I owned a truck equipment shop for a day or two. Built bomb disposal trucks, surveillance vehicles, swat vehicles, custom load semis, up-armored vehicles of all kinds, etc. Down about 3500 frame mods of all types. the old timer had a theory used by many.
re: tapping frame or glove - Only problem is the tapped threads create a starting fracture inside the metal that goes bad in time. Different heavy equipment companies tried it over the years as well as a few car mfrs.
The reason for grade 5 is it has proper tension capacity, and stretches rather than shears. Clamping force of 1/2" diameter bolts x 8 of them, if your gloves are made the right size, you will be plenty tight. When lateral torsion will create a problem you insert an internal rectangular glove, using captive nuts inside and enclose the outside glove with a interior cap plate.


Doing a repair like this then using it commercially? nope. More bad stories than you could think of. WW is right about insurance ability to deny liability, and not by state it hits federal laws. My company built every tow truck and boaster truck for the largest tow co in Vegas, as well as over half for their next 3 sized competitors in the time I was in business. The stresses on towing frames are not crazy bad, its just the service time that makes it so much worse being maxed 25-50 % of the time.
If things go bad you might not go out of business. One of the fuel companies that was my customer, later becoming my employer, had 13 deaths to their liability in just 1 year span that I am aware of. many before and many after. They just pay out the nose for insurance and bonding. Be careful.

 

[GM Guy]

Thanks for all the replies guys, I was mostly wondering if this could be done safely.

For a farm beater/ service truck that at most would support a service body and pull a car trailer with a combine tire on it, I may go ahead and repair the current frame.

But its looking like for a cross country gooseneck rig, I am best off with a frame swap. I am aware of the safety implications, there is a reason I keep the ABS working and have a high quality brake controller, I do like good brakes.

on the topic of a frame swap, are 2500HD and 3500SRW the same frame? if not, the 2500HD is surely heavier than the 2500LD, correct?

was I correct above in my statement that finding a frame with a matching plastic label would be correct? (the plastic label on the right side, under the cab, in a hole in the frame) if so, I am sure there is a gasser automatic job kicking around a junkyard that I could frame swap.

thanks guys!