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          It's not an easy task messing around with the windshields on the pre-Advance Design trucks (pre-1947). Because they open outwards, they have a frame. And that frame has a seal. And that seal can be darned tricky to replace. Not anymore! Here's Mike to walk you through the ...

Windshield Gasket Replacement for pre-War GM trucks
By Mike Reese
1940 GMC 250 Stake / Flatbed
1951 Chevy 6100 Dump
1951 GMC 350 Fire Engine
1951 GMC 720 Rescue

Kempton, Pennsylvania
<<<click on images for larger view >>> February 2009

Replacing the rubber around the windshield

As with most old trucks, over time the windshield rubber becomes dry rotted, cracked and eventually leaks. On my 1940 GMC one-ton flat bed / stakeside, this was the case even though it was always garage-kept. I decided winter was the perfect time to replace the rubber.

I removed the windshield and went to work on the bed of the truck. It was at this point that I thought, "Well as long as Iím this far, Iíll get the glass replaced."

First, I removed the windshield connector and top and bottom tee connectors. Next, I removed screws that hold the inner and outer center division bars (the longer screws go on the top and bottom of the center bar) and carefully removed the outer bar with care as to not to destroy the rubber seal that is part of the center bar.

I cut the windshield rubber at the top and bottom to separate the frames after I removed the screws that hold the frame together. The frames were rusted to the windshield connecting bars which slide into the frame to give it form and structure. I was able to save the frames but the bars needed replacement.

After the frames were separated, I dug out the remaining rubber on the outer frames channels. I carefully removed the glass and headed to the glass shop.

The glass shop installed and sealed the glass in the frames and joined the two pieces with new connecting bars and screws but they would not install the rubber gasket that goes around the frame. I asked for some tips and I was told to spray the rubber and frame channel with Windex and they gave me a long narrow-tipped plastic tool to use for pushing the rubber in as I go.

The rubber I bought had glued ends and that is a good feature because you can get it not glued so when you get it installed, there are no issues. I found it to be fairly easy to install it using Windex but in places the rubber was loose in the channel, which would allow water to get in the channels and it would leak. So after some thought, Iíd try it with some 3M super seal weatherstrip and gasket adhesive so I removed the rubber and was starting over.


I got everything laid out on my seven foot long kitchen table that I thought I would need. It was a brain test trying to determine where would be the best place to do all this, where I'd have enough space and plenty of elbow room.

Here's my tool and supply list:

  • two 1" plastic putty knives
  • latex gloves
  • box of Q-tips for wiping any excess 3M sealant
  • pack of women's make-up remover pads for wiping break cleaner
  • plastic tool from the glass guy

i then taped both sides of the frame [ picture ] to keep from making a mess on the rest of the window and painted frame. This 3M stuff can end up being messy if not careful.

Since I was doing this alone, I needed some help so I used a wood clamp to help hold the window [ picture ]. I slid a rubber hose over the exposed clamp so not to scratch the painted frame.


Here Goes

It was time to get started. What I learned the first go at it was to have the frame sitting on the table the same way it sits in the truck, and position yourself to work from the "cab side" of the frame. I started at the top right corner and laid a bead of 3M in the channel all the way across to the left radius and left the sealer skin over. (The directions say to put a bead on both the pieces that are to be bonded but I didnít, figuring that any excess will find a place to fill any voids.) I found that if I inserted the rear side of the rubber in the channel first and put some forward pressure with my thumb, and use the tool to push the outside of the rubber into the channel, it helps in getting the rubber over the lip and seated -- which you can feel it seat. .

Iím left handed thatís why I started at the upped left corner.

I laid about 4-5Ē on top of the frame and started pushing until it was seated. I worked a few inches at a time until I got to the top left radius The rubber is easy to get in the radius but is tougher to get fully seated. (Thatís where the plastic putty knife comes in handy.)

Once around the radius, I stood the frame on end, on the floor, and continued. When I got to the lat radius, I moved back to the table top. I had to really stretch the rubber up and over the channel. I tried to have the glued end of the rubber in the bottom center of the frame but I guess from working it, I was on the right side when I was finished. On the bottom, where the two frames meet, the rubber wanted to roll inward and it opened up the area at the center division bar. So I filled the area with 3M and laid the frame flat so that the weight of the window held it in position.

Where the division bars meet the frame, fill that area top and bottom with 3M real well so water canít seep into the channel before you seat the rubber. Any excess will ooze out [ see the picture at left ].

At the last moment, I used lighter fluid to clean up any excess 3M instead of brake cleaner. I was surprised that I didnít make a mess nor did I get 3M all over me.

I noticed that in some places, the gasket is tight. In other places, I can wiggle it. That is from the differences in the window frame from when they stamped it.

When I put the rubber on the first time, it took about and hour. When I did it the second time, it took less than the first quarter of the Steeler-Ravens playoff game. And I thought having the window frames powder coated (instead of regular spray paint), would make a better finished job.

I bought the rubber and division bars from Jim Carter (and don't forget Jim's Stovebolt Discount) with the ends glued together which ended up being a real plus.


Looking back it wasnít as hard as I thought it would be.



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