• portable drill
• 1/4" drill bit
• ruler/tape measure & sharpie
• metric socket or nut driver set
• phillips #2 screwdriver
• flat blade screwdriver (for prying)
• automotive grease
• wire cutters and wire strippers
• electrical tape or shrink wrap
• solder and soldering gun (optional)

2+ hours

Initially, GM used a very poorly designed power window regulator in the C4.  This regulator, commonly referred to as the "ribbon style" was prone to failure, and wisely redesigned midway through the 1986 production run.

The early style regulator, show at left, has a sealed motor, and can't be easily serviced.  If the flimsy ribbon doesn't break, then over time, the grease on the ribbon attracts dirt and hardens, packing grime into the motor, slowing it down and eventually overloading it.  Both of my units were slow and noisy when I purchased my car, and made it seem cheap and old.  It wasn't until one of the ribbons snapped, and the entire window crashed down into the door innards, that I finally decided to upgrade.

The newer style regulator, at right, uses a "scissor style" assembly, driven by a steel gear.  It operates quickly, quietly, and doesn't depend on a thin nylon ribbon to carry the weight of the window.  They can be purchased for anywhere from $120 used to $500 for a new set.  The only modifications required involve drilling two carefully placed holes in the bottom side of the door, and a very simple modification of the passenger side motor wiring harness.

Put both windows in the down position.  For safety reasons, disconnect the battery's negative terminal or pull the courtesy and power window fuses.

We'll start out by gutting the driver's side door.  First, slide the manual door lock lever forward.  Now get a finger behind the front edge of it, and pry the plastic piece outward towards you.  If it feels like you're going to break it, or your finger, you're on the right track.  This is the most difficult part of the entire process.  After that little piece comes flying off, push the lock rod rearward, and slip it up behind the clearance cut into the plastic surround, otherwise it will get interfere with removal of the door panel.

The inner door panel is held on by phillips screws.  There are several spaced out along the lower edge of the carpet, one behind the door handle, three in the plastic that surrounds it, two in the arm rest hole, four in the speaker cover, and one on the back edge of the door panel near the hatch release switch.  After removing these, slide the door panel upwards and it should come loose.  Be careful, since there are still electrical harnesses attached to it.  Unplug the rear hatch switch's wiring, and the window washer control harness.  The door lock switch's plug must be pried out evenly.  I found this quite difficult to remove, so I took the extra step of removing the plastic door latch surround first.  To do this, first remove the two phillips screws that go upward into the courtesy light.  The arm rest pad also needs to be removed.  There are two molded-in teeth that clip it on to the door panel.  One is located about 1/3 of the way toward the back of the fat horizontal part of the pad.  The other is near the top of the inclined part up front.  Push the pad inwards towards the door panel while pulling up on the inside edge of the pad (in each tooth location).  Once this is loose, remove the arm rest plastic piece and set the pad aside.  The plastic door latch surround can now be dislodged from the door panel, and fished back through it with the wiring still attached.  Set the door panel aside.  The courtesy light plug is brown, and the door lock switch can now be accessed more easily.  Three pins protrude into the plug, so pry the plug off evenly, so as not to damage the pins.

After peeling away the clearn plastic cover, your door should look like the photo below.  The four wire harness plugs that needed to be removed are highlighted.

Next, the inner door metal needs to be removed next.  It's held on by hex screws, door lock/latch rods, and the wire harness clips.  First, detach the wire harness from it, and remove all the hex bolts and screws.  The two lock rod clips are circled below.  You'll need to get your flat blade screwdriver back there and pry the rods out of the plastic clips.

The door latch rod is held onto door handle by a small metal clip.  The clip can be slid partway off, allowing the end of the rod to slip up and out of the hole.  The lock rock is a little more tricky.  It loops through a metal pivot that also attaches to the door lock solenoid rod.  I simply bent the metal tangs enough to slip the lock rod out.  The door lock solenoid rod is attached to the pivot with a small nylon clip.  Rotate the clip slightly and pull the rod out the slit in the backside.  Make sure to lay the loose lock rod outward on the fiberglass, so it doesn't get interfere with the regulator's movement.  The inner panel should now be completely detached from the fiberglass door frame.  Push it downwards into the door until it clears the top edge of the frame, and slide it out.  You'll need to really slide it forward and around to get the lock rod disentangled from it.

The next, very important step is to remove the window stops.  There's one in front, a simplistic folded (and very sharp) steel bracket held on with one hex screw.  In the back, is a bracket with 'fingers' that engage the window regulator.  It is held on with two hex bolts (now only one, since the other was removed to pull the inner door panel out.  Also loosen the two upper felt pads that support inside surface of the window and slide them back away from the window.  You'll then need to hook up battery power so you can raise the window slightly.  The photo below shows the door with the inner panel removed.

I traced a line around each window bolt to aid in lining it up on the new regulator.  Now the three window bolts can be removed.  Carefully draw the window out of the the upper door slot.  A helper would come in handy here, to make sure the window isn't dragged against anything.  The window studs and the front window stop are attached to the window, but there are clearances in the upper door slot for all of these to pass through.

Move the window regulator back to the down position and unplug the motor.  The photo at right shows the door with the window removed.  The regulator assembly is held on by two nuts up top, two bolts on the bottom edge, and one on the side of the door, shown clearly in the photo.  Tilt the regulator back, and pull it out the side of the door, top first.  Make sure you don't let the wire harness sit in the door bottom.  Here's a pic comparing the old and new regulator side by side:

Now comes the fun part.  Bust out the drill, it's time to cut some holes in your Corvette.

From the hole on the middle of the door's bottom edge, measure 5-11/16" (that's 145mm for you French bums) rearward and mark a dot.  The holes should be measured center-to-center and be spaced equally from the inner door edge.  Mark another dot 2-15/16" (75mm) further rear from the other dot you marked.  The hole locations should look something like what's pictured to the right.  The factory hole in the center of the door bottom is where that masking tape ends towards the front of the door.  (Trust me, don't let the perspective fool ya.)

Drill a 1/4" hole at both marks.  If you're vette is lowered like mine, or if your drill is too long, you may need to jack up the side of the car a bit.  I got lazy and just started with a smaller bit, drilled at the slight angle, then started with the 1/4" bit.

Now lube up that new regulator and toss it in.

Here's a potentially important note worth mentioning.  The instructions I used stated that the forward-most window stud must be shortened by 1/4" (7mm).  I used a dremel cut-off tool to accomplish this, but upon installing the window and moving it up and down, I found it to be an unnecessary waste of time.  If you're the paranoid type, or it makes you feel any better about continuing, go ahead and shorten that stud.  But you're wasting your time.

And another tip before the window goes in.  The cone shaped front window stop can be a source of constant rattling.  It's free to pivot and rattle on it's attachment for God knows why.  Put a dab of glue on it to keep it stationary and quiet.

Here's a pic with the window installed on the new regulator.  I used the markings I made on the old regulator as a reference for relocating the window in the square holes of the new one.  It'll still take some adjusting to get it right, so don't slap the door panel on and slam the door quite yet.

Once the window is mounted in there, tighten up the upper felt pads, to keep the window from dragging against the door innards.  Put the window stops back in also.  And one more thing... if you bought these regulators used, you most likely don't have the bottom stops that go in the forward most hole on the bottom edge of the door.  I didn't have these pieces, so I cleaned off the surface and put two layers of heavy duty weatherstrip there.  If you leave it unprotected, the window regulator's track will hit the door's fiberglass bottom at the end of it's travel and make a big thud noise.  This picture to the right shows the placement of the adhesive weatherstrip.  Yes, I know it's ghetto, and will probably come loose eventually, but I used some glue, so hopefully that'll help.

You will need to cut the electrical tape back in order to plug the window motor back in, since this one is positioned further away.  There's plenty of slack in the factory wires to accomplish this. Now test out the motor, make sure it does its thing.  Move the wiring harness out of the way such that the door can be shut most of the way without it pinching anything against your door sills or dash.  DON'T latch the door yet, unless you're comfortable getting it back open with no door linkage in place.  Adjust the window stops and the three locating screws until it's positioned good enough to allow the door to close without the fully raised window colliding with the B-pillar or roof frame.  Now you can start reinstalling the door innards.  The inner door panel has holes smartly cut into it to allow access to the window adjustment screws.  The window stops, and upper felt pads will also need to be adjusted.  This is mostly a trial and error process, which took me about 10 minutes to complete.

The rest of the reassembly is straight-forward, simply the reverse of removal.  Don't forget to plug in all those switches you disconnected behind the door panel.  Also, don't forget to pull the lock rod back through the cutout on the plastic door handle surround.  If it's in the way, you'll spend all day trying to smash the door panel into place with no luck.
 

There is only one significant difference from the driver's side procedure.  After you get the window out, and remove the old style regulator, you will need to reverse the wiring to the motor ON THE PASSENGER SIDE ONLY.  The plug in question is shown below.  If you neglect to do this, the power window switch will work backwards on that side of the car.  Cut and splice the wires and wrap some electrical tape on it.  (If it's good enough for GM, it's good enough for me.  I always use high quality 3M electrical tape.)

Installation is reverse of removal.  Now, you'll be able to drop those windows in no time to conceal your illegal tint when those pesky police officers pull you over.