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Truck frame rust repair...

13K views 17 replies 9 participants last post by  maverickmechanic13 
#1 ·
Hello everybody!
One of the trucks (SUV actually) that i own is a lifted 92 2 door GMC Yukon. This past winter i noticed my back bumper started rotting through really bad (popular phenomenon in NE ohio due to all the salt). In the spring, i decided to remove and replace the rusty bumper. Easier said than done. With the bumper removed, i noticed the frame perches that hold the cab supports failed, and the body mounts fell through. No problem - i can alway take some angle + plate and make magic happen...
after cutting off what was left of the cab perches, i noticed the frame itself was paper thin for the last 8-12" of the rail's legth, on both sides, moreso on the passenger side. i started cutting and sawzalling in hopes that i can find some decent metal to pick a starting point, but it turns out that that the leaf spring shackle was a hope and a prayer away from ripping off the frame.
So... my dilemma is - on the passenger side - how does one replace / beef up that frame section? leave the existing paper thin frame in place and start adding plate, angle and reinforcement fish plates over top of whats there? Do i cut a template out based on the driver side frame rail and mirror it for the passenger side and work off that? completely cut that frame section and start anew?

Any help would be tremendously appreciated ...

P.S. the tiny kitty is giving me the silent treatment... he doesnt wanna talk...
 

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#3 ·
You want an opinion from a guy out in sunny California where I have 50 year old cars with zinc plating still on the body bolts and I can unscrew them without so much as a grunt with a 3/8 ratchet? I say that truck is a goner, dump it, get another, it isn't worth fixing.

Brian
 
#6 ·
im not in a rush to fix it. the truck is just a toy. It is not a daily driver. Unfortunatelly rust is a problem we have to deal with in the north east. Scrapping the truck is the easy way out. I'd like to fix it and fabricate something for it. All im asking for is an opinion on how to repair it.

I looked at a few frames in the bone yard... not much better. by the time i cut out a frame section from another truck... i can fabricate the same piece from new steel... and be better off.

I guess my question is - where to cut and what to use, from an experienced person's point of view.

Thank you for all the info.
 
#12 ·
im not in a rush to fix it. the truck is just a toy. It is not a daily driver. Unfortunatelly rust is a problem we have to deal with in the north east. Scrapping the truck is the easy way out. I'd like to fix it and fabricate something for it. All im asking for is an opinion on how to repair it.

I looked at a few frames in the bone yard... not much better. by the time i cut out a frame section from another truck... i can fabricate the same piece from new steel... and be better off.

I guess my question is - where to cut and what to use, from an experienced person's point of view.

Thank you for all the info.
I hear you, that's your choice, sorry I ranted in my "editorial".

Brian
 
#7 ·
If it's just a toy and you want to fabricate it. Back half it and 4 link it. You'll get a little more travel that way also... You can repair it any way you want but those rails are shot so your going to need to replace the entire rear section and not just patch.. If you keep the geometry the same with the shackle hanger, it will be golden... If I was that deep into it tho, I would back half it, 4 link it and be done with it. Repair the body mounts accordingly
 
#8 ·
Find a spot on the frame that is good (or atleast the best) and use that for a guide to your thickness (guessing 3/16" to 1/4"?). Then get a flat piece of metal that thick and either cut out the pieces and weld it up or brake the bends to match what you are replacing. If looks aren't as important as function, then you could probably use channel iron as replacement pieces and save a lot of time and money in fab. Just be sure to plate or box the areas you repair to ensure safety and strength. Never put a straight up and down weld on a frame, as you will almost certainly have a crack form on either side of the weld. When you cut out the bad area either cut it at an angle (45 degrees) or use an off set cut method (cut down to the center, then cut straight back,then cut down). If you don't mind shipping costs and changing everything over, you could probably find a rust free replacement frame in another part of the country for a little more money. If it sees a lot of off road use, you could use the factory frame to get measurements and dimensions and build a custom chassis out of round or square tubing if you have the skill level and time. Several options just depends on which way you wanna go.

Here's an example of an off set cut on a frame.


Kelly
 
#9 ·
I'm with Kelly ....Those guys on the west coast are a bit spoiled doing the easy stuff all the time...so when it comes time for real work all of a sudden they turn french and run....:mwink::mwink: only kiddin .....the french dont always run...:D
Usually I'd say jack it up and get under there .but it looks like you got that part covered and you dont need jack stands either so...so visit www.carparts .com and see whats out there we have bone yards here that are full of that stuff and all in great shape...getting it there is the hard part..
One thing I would do is inspect the truck very carefully to see if theres any tellteale signs of more rust in the body ,as you found out with your bumper replacement, things have a tendency to snowball ,and you could be opening a big can of worms...
 
#10 ·
I agree with Martin. The frame is thick, mostly everything else is not. What does that tell you? As mentioned, we are spoiled in CA with rust free cars. Heck, I fixed a couple patches on my Mustang and other than that it's like a brand new car! So with that said, if there's other options with a lot less rust I would jump on that.

In regards to people in CA running away from rust...it's ok as long as we have guys from your state running TOWARDS US to get CA cars. :D
 
#11 ·
I have sold a couple of cars that went to other parts of the country, one to Michigan and the other to New York, both of those cases they were blown away when they got their "new" car and looked it over. They contacted me telling me they had never seen a car so nice in their life! So yes we are spoiled. This truck is FULL of rust, it isn't a classic, it's just a truck, replace it, it's not worth "working on", goodness knows anything you realistically isn't "repairing" it. Not unless you are going to do what John is doing to his 53 Chevy convertible, which is simply not realistic with this particular truck, it's "just a truck".

My opinion, that's all.

Brian
 
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#13 ·
Ok, let me say I understand where you guys are all coming from,especially the west coast guys that don't have the rust issues that the NE and MW have. Is the truck worth saving? that is a question only answered by the owner. Personally if it were mine, I would try to find a better chassis and body with a bad engine or trans and swap in the mechanicals of the one he has. However, if he wants to fix it that is his choice. Maybe it has some sentimental value, or he is wanting a project to work on without spending the money to buy something he is un familiar with that is hard to find parts for. Look at it this way, if he fixes the frame and body on this truck, he will gain loads of invaluable experience, and have something to be proud of that he can say he built. Will he have more money in it than it is worth? Most likely yes, but if we all based our choice of projects on monetary value, we would all be building SC Cobra's, Shelby mustangs, 427 vettes, and COPO cars.

I did have a thought as I looked through the pictures again. To the OP, if you decide to repair this truck, when you get the frame repairs completed I would take the time to completely box the frame. My reasoning for that is this, if you look at the "C" channel design the frame has now, it is nothing more than a shelf for the salt, dirt, water, and whatever else the tires can sling to lay on and rust. If you box the whole frame, then the junk has no where to sit and form rust, preventing (or at least helping prevent) the problem in the future. Also on the rear bumper, if you didn't mind using a painted factory bumper, or a custom home built one, I would also box in the back of the bumper in regards to the theory with the frame. Then use a bed liner product on the frame to help protect it against corrosion.

When you get the frame taken care of and in good shape, then start on the body. When you get the mounts, floor pans, and other panels fixed on the bottom, you could spray a bed liner product on the bottom of the vehicle to help in postponing the rust problems again.

Just a few random thoughts FWIW

Kelly
 
#17 ·
A new roll over

Were are spoiled Up here in the rockies too. I would look for a almost new roll over truck for the chassis. How is the rest of the body for rust. ? My nephew from N Calif sold His Mopar rag top a couple years ago that he won a second place trophy at the GNRS On line to some one back east. He said he tried to be very honest showing lots of picts and shots with the car up on his hoist. There were a few spots of surface rust underneath. The guy that bought it was elated,He said it was a lot better than what he expected for a 50 year old car.
 
#18 ·
Thank you everybody for the input. I haven't been able to do much lately due to rain and work. Hope to get back at it soon.
I decided i m going to cut the thinned out section where the 4 hanger bolts go through and make a new section that starts a few inches ahead of the hanger all the way to the back based on a mirrored template from the other side. ill recreate the top section of the frame from a piece of plate and when its welded in place ill fish plate it with another section of plate that would overlap the patch and add some angle sections at the 90* bends of the frames c-chanel.
for the driver side ill just cut a patch plate to weld to the inside of the frame, with added angle sections for reinforcement. Also, ill reinforce a few more sections while im at it. Ill post some pics as i get to it.
 
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