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Frame twist

Today I mounted the box onto my C10, everything going good until I started scrutinizing. The up and down gap between the cab and the box on the drivers side was at much more of an angle the passengers side, closer at the top and father away at the bottom. Then I sat down on a stool and sighted across the truck and it hit me , the drivers side of the box was way jacked up. So I got the tape measure out and rough measurements put the rear drivers side of the box 1.5 inches higher than the passenger side of the box. I started measuring on the frame and things arent too bad in front of the rear axle, but get closer to and then behind the axle they go south quick. The measurements on the frame mirror what is shown with the box.

So now Im faced with how to go about trying to at least get this in the ballpark. Does anyone have any suggestions?


Trying to be the best me, I can be
First question, do you see any evidence of previous crash damage? I've been doing heavy collision for a long time and usually twist like that is a secondary result of crash damage. First thing to do is to check the center section for squareness. Visually break down the chassis into 3 sections, front center, rear. Look for symmetrical holes and do cross measurements. I'd be willing to bet it's not square. Probably a condition we call "diamond". Even if it is square and simply twisted there is no way to repair it without being able to tie it down to the floor so you can either jack or pull down one side while holding the other side. Unfortunately without a way to tie down and pull repairing this is going to be out of reach for you at home. Best thing I could tell you, if it's a roller find a competent Body Shop that can pull it to get it back in alignment. It's not going to be difficult for an experienced guy with the equipment especially if the cab and box are off. Main thing is finding someone who is competent to pull it. That is going to be harder than you would think as competent frame guys are getting harder to find.
As far as I know its never been in an accident, but it was used as a work truck back in the day so its hard saying what kind of action it saw. I have done quite a bit of work to the frame, it was cut down from a long box and I put in c-notches. When we cut it down to be a short box frame everything was squared and leveled, but that work was under the cab. The c-notch is right over the axle and Im almost leaning toward the c-notch being the culprit. The more I thought about it that was the thing that stood out as it is in the area that things went south. When we put the c-notches in we cut the frame and just put them in, they used some existing holes so we never checked anything other then lining up the holes, its pretty likely something shifted in that process and was never caught.

I have brainstormed some stuff to try at home first. Like you said the main thing is finding someone competent to pull on it, and that is probably the part that has me most worried


Trying to be the best me, I can be
If that's the case Sprint then you are gonna want to undo what you did and re-do it. If it is misaligned from cutting the frame and re-welding then putting it on a frame machine and pulling it is not going to do any good. Going to have to get the notches right.
It sounds like verifying the notch is the problem is the right way to go. Sounds like you can adjust the spacers where you are mounting the bed to the frame to make it look straight if you trust the truck will ride straight to jury rig it. The people that might notice are just too close.
I've got to do some more measuring to figure out for certain.

It appears initially it's only up and down I have to worry about, the side to side of it looks right on.

I'm not opposed to doing some shimming but I'd like to get within a 1/4 inch before I consider that.


Trying to be the best me, I can be
I sure as hell wouldn't shim it, if it is 1 1/2" off.:eek: 1/4" would be okay. Get yourself a laser level and set it. (datum line) Measure to the laser as opposed to measuring to the floor. That should be much more accurate.
Bolted and welded along the top. I figure I'm going to have to cut the weld and unbolt it.

Before the c-notch rough measurements put the two sides within about an 1/8, after the c-notch they are a half inch off. I'm fairly certain this is where the problem is.

How good does SPI epoxy work over powder coat, no different than anything else? I'm trying to figure out how to do the least amount of damage and then dress it up when done.
I think we managed to trace down most of my issues. I found a combination of things adding up to what I was seeing.

1st thing is the frame is off a 1/4 inch, we blocked the frame level, and leveled a straightedge on the floor and more or less this is the measurement we came up with.

2nd thing is the floor in the shop is way off when you start scrutinizing it.

3rd thing is when we prepped the truck to set the box on we spun it 180 degrees using wheel dollies. The c10s of this era have a panhard bar to the drivers side frame rail right behind the c-notch. I think when we pulled on it to spin it around some load was transferred through that bar pushing up on the frame. Im under the impression that most of my issues were because of this.

4th thing is with the suspension. Im off a little here between each side, Im not sure why or where its off. It measures like its the coil spring, but they were swapped with no difference. Im wondering if I have a trailing arm off slightly. I put a temporary shim in one side and everything lines up really nice. I still havent really decided on anything final on this until I get on a better surface and get full weight on it, if anything I might make a more permanent shim if needed.

Given all that we tried installing the box again last weekend and it was smooth sailing for the most part, a couple 1/4 inch shims in various spots and everything lined up pretty good. My body lines from cab to box lined up good horizontally and vertically. All the mounting bolts ended up for the most part just dropping right in.
good for you. I just found out why my Chevelle was so hard to push finding a 3/4 inch bend in one of the axle tubes from the center. I knew it was a truck rear end, did not expect it was from a tow truck. Hard to push pigeon toed cars.

Glad you found the answer.
I'm very relieved to have found what I did. It's no big deal to cut and chop on a frame, but it's a hard pill to swallow when it's in powder coat and you have hopes of driving in the next few months. I know I've been sleeping alot better this week, lol.