The Stovebolt Site Forums The Shop Area Paint and Body Shop 55 GMC repairing rusted windscreen frame

Hello forum,been away for awhile but back at it now.Have replaced both lower corners so far,Have a VG top half of a cab I am using for pieces to replace the rusted bits. The top over the windscreen is rotten so need to fix that.Thinking of replacing the whole roof including the upright pieces on each side at the front These are rotten also.I am thinking lots have been there before me.? Going slowly here as dont want to completely screw this up.Athab3

Here are some pics with a larger view,Trying to show my rusted areas and a view of the replacement top.Athab3

I have had to do those exact repairs. Lower windshield corner i actually fabricated myself. I had holes in the roof panel all the way around the cab near the drip rail as well as above the windshield. Replaced both the inner and outer roof panel. It actually went way easier than I expected. Run some interior bracing to keep everything squared away, keep the doors on so that you can make sure the new roof lines up with them, then just follow the factory body seams. You will need to drill out about 100 spot welds to separate the panels.

Do you have rust through all the way around the top of the roof? If it is just up above the windshield, they make those two patch panels now and you wouldn't have to do the whole thing. How bad are the A-pillars? if it is just surface rust I wouldn't mess with those.

Roof swap: https://photos.app.goo.gl/T86g0LLLPL5nZyJs2

Thanks Gumbi,The top is solid everywhere cept accross the top and the top bits of the A posts.There was mouse droppings and hornet nests in the void over the windscreen all accross and of course over time it caused the rot .The metal of the outer top is fine but will need some cleaning up. I had heard that these panels were available but havent seen them for sale online anywhere yet.Was thinking I could run a cut just below the eyebrow and use the piece from the good top.I did cut out the rotten piece over the windscreen but only the inner bit as the outer piece is fine.I will take some more pics of the A posts rot and the inner bit over the windscreen.Athab3

some more pics of the rust problem on my 55

some more showing the good" pieces.Athab3

Thanks Bartamos. Going to go slowly on this issue.Have another project, TR 6 Triumph ,my sons , on the go so will switch to it for a bit and ponder the rusty windshield frame for awhile. Athab3

Oh Oh lost bartamos's post

I didn't like my advice and re wrote it. Sorry buddy. Didn't mean to mess up the thread.

We have had others with this rust area. This is THE most dangerous and difficult fix you could have on that truck. The welding is not a problem. Welding is welding. You look like you are doing a good job. The problem with the TF trucks is the wraparound windshield. The shape. The sort of compound curves. That windshield is one of the most difficult to install. IF the opening is built by the factory to one side of the tolerance zone and the Chinese glass is built to the other side, it's a nightmare to get a fit that seals.

Cutting out pieces and fitting them is a little risky. The weld gap you leave/the fit-up you do is hard to measure. Hard to be sure you have maintained the opening to spec. Some days for this repair, I use the rule of thumb: Only repair the rusted area, don't cut anymore than is necessary. That's fine for all the rest of the truck. But some days in order to maintain factory shape, the pinch weld and windshield rubber fit, I think it's way better to install the whole window frame or whole top.

I'm sure you have ideas. I think the straight sections, bottom and top, would not affect the opening size. Except possibly the "Y" axis/Height. Easy to measure. The problem is replacing areas at the curves. One method is a template with registration marks in either side of the cut. Marks on the truck opening in places not being cut; and marks on the template that match. Use the template, with marks aligned, while tacking the patch. The cardboard template should lay ON the pinch weld and should match the opening curvature not the pinch weld, I'm thinking. If you have cut the truck already you can use the donor for the template. You must take all the measurements and templates you can before you cut.

You need a second donor to go back and measure as you patch.

As said, temporary support is need if you think your cut will cause movement/sag/etc.

Any area that does not affect the glass opening, would, of course, be a normal patch made from the donor or vendor.

Thanks for that Bartamos,Im gonna think and look lots before any cutting .Will make a template that fits in the opening with zip cut marks for reference ,they can be welded back in,.Athab3

I would almost recommend sheet metal templates tacked in place on the good parts of the pinch weld. THEN cut out the bad stuff and get that tacked in before cutting off the templates. That would serve two purposes, stiffening the opening and maintaining the correct shape. It would also give you something to clamp your patches to for welding. Cardboard is a little hard to weld in place.

That would only apply though if you're leaving the majority of the good metal in place, not for replacing the complete top.

Good Luck. Looks like you have a handle on it. Spending some time studying the situation is always good. Falls into the category of "measure twice, cut once."

Maybe this is what you already said. Not sure what a Zip cut is:

Another method on the curves would be to cut the donor piece "longer"/past the rust, place it on the truck and cut both at the same time. Then use "spacers" using the same thinckness cutting disc you used, while tacking....or registration cuts/marks. Check it all with the template and etc.

Many other countries do not have the same "auto insurance" we do. They NEVER total a car. They keep ALL crashed cars. The many, one or two guy, independent repair shops, get a donor for a whole section, including quarter panel with door opening, hatch opening, etc. They cut some of the damaged skin off/drill the spot welds, then "pull" the structure back to spec, weld and repair that hidden part, then they remove spot welds from the remainder bad skin. Then get the skin/sheet metal they need from the donor. Lay the whole piece on the car and cut them both at the same time, as I mentioned. Two difference there. Cars now are built with inner structure and outer skin, sort to speak, and secondly they have factory registration holes, or features, which the repair person uses to match up, as he cuts both at the same time. You get the picture to think about for your repair.

Zip cut is just a slot cut into the good metal that will remain.I use this method to get a datum to measure from when doing MGA inner sills.I found out ,sadly,long ago that a sharpie mark didnt stay on with sanding and priming etc.DUH!! What was I thinking.Like the sheet metal templates.Thanks Shop Shark Athab3

This could be something.