The installation instructions that come with the windows are worthless, and do not seem to apply to this type of installation. I haven't found any YouTube videos that could help, either. Fortunately, I was able to enlist the aid of an auto body fabricator who had done similar installations in the past. We figured out how to do this one together, with a little trial-and-error along the way. I had made the template beforehand, and the positioning, marking, and installation process took less than three hours for both windows. Hopefully, the details provided below will enable someone else to do an efficient, error-free installation.
1) Figure out how all the parts will go together:
The reversible aluminum retaining ring ("trim ring") will go on the inside of the van. It comes with pre-drilled screw holes. For mounting the sliding window in the 1/4" thick plastic panel in the van's sliding side door, the plain side of the ring will need to face the interior of the van.
Remove the shiny aluminum clip that is crimped in place to hold the two free ends of the retaining ring together for shipping . This can be most easily done by using a cutting wheel to slice through the "spine" of the shipping clip. The split in the retaining ring will be positioned at the bottom of the window. Use a piece of painters tape to temporarily hold the two free ends together in alignment after the shipping clip is removed.
The window frame holding the glass and screen will attach to the outside of the van. It has two narrow grooves that run around the entire perimeter of the frame, facing the van's interior. The innermost groove is for the spline that holds the screen in place. The outermost groove is for the screws that will clamp the retaining ring to the window frame, compressing the sealing gasket and holding the window in place.
2) Figure out where in the door panel the window will go:
Because the opening in the van's sliding door frame is tapered toward the rear, you will want to position the window as far forward as possible. I suggest having the fixed glass portion of the window toward the front of the van. The way you position the window will determine which part of the window frame will be the top. Label your windows as driver or passenger side, and indicate the part of the frame that will be the top. Use the black rubber plugs that are provided to seal off the top four weep holes on the outside of the window frame.
3) Make a template for the window cut-out:
Use the edge of the first angle to the outside of the pre-drilled screw holes in the retaining ring to mark a piece of sturdy paper, tracing all around the ring. Cut out the template, then fit it inside the retaining ring where the window frame will go when the two pieces are screwed together. Make your final adjustments, paying particular attention to the fit at the radiused corners of the window. The template should measure 14.0 inches by 21.5 inches. Tracing around its edge onto the panel should add about a tenth of an inch to those dimensions. The finished height of the cut-out should be 14.1 inches, and its length 21.6 inches, for a snug fit.
4) Position the template:
Hold the retaining ring in place on the inside of the panel, toward the front of the van, avoiding the door's structural elements, and fix it in place with a piece of tape. Position the template inside the retaining ring, and attach the template to the panel with painters tape. Leave an equal amount of clearance around the top, bottom, and front end of the template. Then, drill a hole through the template and the panel near the front end of the template to help locate it on the outside of the panel.
Remove the template and transfer it to the outside of the panel, using the hole you drilled to position it correctly. Be sure to keep the same orientation as when the template was on the inside of the panel.
Measure from the top edge of the panel to the top edge of the template; it should be the same distance, front and rear. While keeping the hole in the template and the hole in the panel lined up, rotate the template so its top edge will be parallel with the top of the panel. Since the plastic panel is tapered from front to rear, the bottom edges won't be parallel, but installing the window frame parallel to the top of the panel looked best to me.
5) Cut out the opening for the window:
When you have the template positioned the way you want it, hold it in place with some tape, then lay down a swath of wide painters tape from beneath the edge of the template and far enough away from the cut line to prevent scratching the panel when you run your jigsaw over it to make the cut-out.
Use a marking pen to draw the outline of the template on the tape, then remove the template.
Cut out the window using a jigsaw with a metal-cutting blade. You will need to first drill a large enough hole near the corner of the cut line to accept the jigsaw blade. Work slowly and precisely. Plan to finish the cut along the bottom, and attach a piece of duct tape to the top of the cut-out to hold it in place, keeping it from twisting and breaking free as you finish the cut. With a fine blade, there will be no splintering of the plastic, but there will be a lot of dust. Try to contain most of it with a drop-cloth, and expect to do a lot of vacuuming when the installation is finished.
After you have made the cut-out, check the window's fit. It is better to make the cut-out a little too small, and then enlarge it with a sander in the places where it is too tight.
6) Prepare the window for installation:
Lay the window on a padded work surface, and use the retaining ring in its proper orientation (with its split at the bottom of the window) to align the pre-drilled screw holes. Make sure that the free ends of the retaining ring are aligned and in contact. Starting on each side of the retaining ring split, drill shallow holes into the window frame groove where the screws will go, no bigger than the diameter of the provided #8 x 1/2" screws' tip, just to get the screws started. Then, carefully drive in the screws by hand to make tapped holes. Even though the screws are supposed to be self-tapping, it will be quite difficult to start them without drilling first. Work your way around the retaining ring in both directions, screwing in all the screws.
7) Install the window:
Remove the screws from the window frame. One person will need to hold the window in place from the outside, while another person on the inside of the van holds the retaining ring and screws it in place. Tightening the screws will pull the window frame against the panel, compressing its rubber gasket. No additional sealant, tape, or caulk will be needed.
Once all the screws have been started around the retaining ring, move in a circle turning each screw a little. Do this a number of times, moving on to the next one without completely tightening any of the screws at this point. Frequently check the positioning of the retaining ring, window frame, and the rubber gasket, as you tighten each screw a few turns at a time. You want the window frame to compress its gasket uniformly. Continue tightening little by little, until the exterior window frame is tight against the panel, which will create a waterproof seal.
When the window is in place, you will want to clean the glass. Because the window is tinted, do not use Windex or any window cleaner that contains ammonia. Invisible Glass is a product that is safe for cleaning tinted windows.