Square Body Rusted Rear Window Restoration: Custom Hand-Crafted Patch Panels

rusted square body window frame restoration

7 months away from the Project M install date at the Four Wheel Camper factory, I took a closer look at visible rust creeping out from the rear window on my 1983 Chevy K10, nicknamed #BigRedK10. 

Owning the truck at this point for about 4 months, I had just completed previous projects like adding new 37” tires to the old square body Chevy, servicing the rear Dana 60 axle and restoring the truck bed. While I was finishing up the bed, I started poking around the rear window. Curiosity grew to just pull the window entirely. What I found was completely overwhelming. Removing the rear window and the cargo light revealed that rust had almost totally destroyed the sheet metal beneath them. Much of the pinch seam needed to be replaced, along with the window frame itself. I had no idea the rust was this bad around the window when I purchased the truck.

Stuck with only basic shop tools like carpenter and auto body hammers, vise grips, various steel straight bars and more, I decided to try and tackle custom fabricating new patch panels to replace the rusted out metal and restore the rear window. I had no idea the window was in this bad of shape, and I had just spent almost all my budget purchasing the truck in the first place. 

With no previous experience, I spent 5 months obsessively working 7 days a week to level up my skills, restore the window frame down to factory spot weld placement, and ultimately, persevere. It wasn’t just about fixing the truck anymore. It also became a personal journey into developing new skills performing custom sheet metal fabrication and restoration to a high level.

Sheet Metal Fabrication for the New Rear Window 

Since I could not find square body rear window patch panels for sale, cabs are now scarce at junk yards locally, and replacing the cab at this point was well beyond what I could afford, the only option was to level up my craftsmanship skills to hand fabricate high-quality, custom patch panels made of of 18-gauge steel. 

The passenger side of the K10 square body window frame was amongst the most rotted sections, so it’s where I started. I used a paint strip tool to remove surface rust, treated the remaining with Rust-Mort, then chased that remaining rust, including pits with a Dremel tool until only bare steel remained. There were multiple holes I poked through around the perimeter of the frame where it was severely rusted, so the steel had been thinned out significantly.

My 1st panel was constructed of strips welded together then ground down. I used the existing section that I was going to remove as the guide to fabricate the panel BEFORE removing the original rusted section, to ensure the correct shape. It looked great, but after installing the panel I quickly realized it was structurally flawed as my welds did not properly penetrate. Bending and shaping the patch panels was the way to go for less welding and a much better quality patch. 

I decided to move onto the bottom window sill and revisit this first flawed panel once I made my way around the window frame.

Facing failure, I had to come up with a way to recreate the shape of the window frame. I got to work with vise grips, straight edges, hammers and more for 2 weeks, eventually coming up with ways to recreate the contours and angles to match the original bottom frame. A contour gauge ended up being a very useful tool for understanding and recreating the shape of the window frame.

Inexperience led me to think I could install the entire bottom frame in one piece, resulting in an entire length for the outer bottom frame sill. 4 separate pieces I hand crafted that were welded together. I quickly learned installing this all as a single section wasn’t going to happen, as the sheet metal below the bottom rear window frame becomes unstable and starts to move as you cut.  So, I chopped the one long piece back into 4 separate pieces.

Once I removed a section of the outer window frame with my Dremel tool and drilling out the spot welds, I cleaned out all the surface rust in the open space, neutralizing it with Rust-Mort, sanding it off then spraying this interior hole with rust reformer to protect the bare metal.  I taped off the spot weld holes prior to spraying to keep from contaminating the new future spot weld.

It took at least a few days to tune the first stretch of bottom window frame before it made for a good fit. Once proper fitment was achieved, I tack welded it in, and stopped there in case I had to shave away any welds to make adjustments.

Next, all the focus shifted to the 2nd and 3rd bottom sections of the window frame I ended up cutting out, prepping the metal underneath in the same fashion. I tack welded in these 2 lengths of patch panel, then arrived at the 4th and final piece to replace in the bottom section of the frame, fitting it into place for a complete, tentative (tack welded) restoration. It probably took me a few days per section, as I had to fine tune each piece with hammers, shaving down edges and sides, etc so they’d properly fit. Each section, I could feel frustration and anxiety wane, while confidence grew out of trial and error. I started to figure out different ways to manipulate the metal with different shaped hammers and objects.  

Next it was time to move forward with finish welding in the new panels. As it seems with every step, this was a lot of work. But in the process, I learned to identify and repeat proper weld penetration,  cutting down on tedious grinding time and touch up welding. The amount of grinding and touch up work I had to do was cut in half from starting on the passenger side, to the end on the driver’s side.

Since the interior pinch seam was in good shape, I was able to use it as a guide for the restoration process, and I reestablished the spot welds previously drilled out.  Mission accomplished custom hand-fabricating a new bottom rear window frame on my K10.

Restored Chevy square body cab rear window frame

Coming up in Part 2, there’s lots of work ahead, but I’ll finish restoring this window frame, take you along for the journey and show you how I went from what most thought was crazy and impossible, to success! Follow on YouTube for Part 2, coming up!

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