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71-76 Eldorado convertible scissor top recover and repair

Started by MaR, June 28, 2021, 03:19:24 PM

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Several people asked that I make a separate thread from my '74 Eldorado convertible restoration thread of just replacing the top and working on the frame. With this as it's own standalone thread, it will be easier to find when searching. Since this is an excerpt, there may be an odd sentence or paragraph that was a reply to a question. It was several posts also, so it will take me a little bit to get it all copied over.


I was planning on started the seat upholstery over the Christmas/New Years holiday but I had an opportunity to buy a really nice complete convertible top assembly. I quickly shifted plans and grabbed the top before it got away from me.

It's an aftermarket replacement top of a good quality manufacturer and it came with all the actuator parts and new weather stripping. I paid less for all the parts than just what the weather stripping would cost.


With the new top safely stored away, I started taking my old top out of the car. The first thing I had to do was take all the interior panels I put back into the rear of the car back out. I then separated the top from the lifting arms. This top is what is referred to as the GM "scissor top". It was GM's first (I think) all electric top and was used on all full sized convertibles from '71-'76. The top fabric and it's roof bows bolt to the lifting arms and also clip to the body shell opening. I had to unbolt the bows and unclip the top from the body.

Here you can see why it's called a "scissor top". These arms are the main lifting arms and when fully extended, form the upper opening where the side glass closes into when the top is up and the window are closed. The ends of the arms lock into the windshield header with pins and the front bow (removed in this pic) has the locking handles to secure the top to the windshield header.

Here is a video (not mine) of an Impala with the same top being run up and down with no fabric on it so you can see how it works:

Normally when the fabric is on the top, there is a cable on each side that pull that back bow and 2nd bow in place. With no fabric on the top, there is no place for the cable to run.


My original plans were to just unbolt the entire top with the lifting arms and actuators all in one shot. It turns out that the whole assembly weighs about 250lbs so that was out of the question. With the top itself out of the way though, I could remove each lift arm out by itself which made the job actually manageable without gantry hoist.


Back to convertible top fun. Here is one of the lifting arms. With the mounting brackets and gearbox, I would say that it's easily 60lbs or more.

The lifting arms seem to be in very good condition with only some surface rust on them. They are exposed inside the car with the top up so they will need to be refinished. I started out by removing the very heavy duty mounting bracket. The bracket weighs about 20 lbs and that large bolt is a 1-1/8" hex.

Next I removed the worm drive gearbox from the arm assembly.

And here are all the parts of the lifter arm assembly. The push bar and middle joint of the arm are all riveted together and at this point, I'm not going to cut the rivets out as it appears that some of them were installed before parts of the arm were welded together.


The worm drive gearbox is very robust and it not an item that commonly fails. It gets it's input power from a central motor mounted between both arms and the power from the motor is transmitted via a steel cable similar to a speedo cable. Both arms are driven by the same motor and synchronization is achieved by manually closing the top with the cables unhooked and then hooking both cables up. The gearbox was not in horrible condition but all of the grease had hardened and it needed to be repainted.


The input shaft had to have the smallest roller thrust bearing I have ever seen. The OD of the bearing is about .375"

The top of the gearbox has a rubber flap that is supposed to help keep debris out of the inside but the bottom of the box had a nice collection of ground up bugs and leaves in it.

I put the drivers side actuator gearbox back together after I cleaned and painted everything.


I then painted the mounting brackets and mounted the actuator back into the bracket assembly.


My top frame assembly is in much better overall condition than the one on the top assembly that I purchased so I have decided that I will reuse mine and just move the fabric over from the old frame to mine. This will give me a chance to completely go over all the parts of the frame and to make sure that the top is as clean as it can possibly be. It does have some soot on the underside from the fire that was in the car it came from. Here is my front bow. The front bow on the top I bought is rusted on the ends so I don't want to use that. The only rust in mine is under the tack strip on the front edge.

I sand blasted it and all the rust came out. There was minimal damage and only two of the tack strip retainer tabs had any rust damage.

One of latching handles had always been a bit stiff. It turns out that the stamping that make up the body of the handle has a little bit of extra metal sticking up and it was grinding into the handle itself when opening the latch.

I ground down the bump and now the latch opens smoothly.


Since I already had the drivers side actuator and arm apart, I went ahead and took the passenger side apart also. It was very similar to the drivers side with minor surface rust and caked on grease in the gearbox plus the ground up leaves and bugs.

One thing that I don't know if I have mentioned before is that this car had almost every nook and cranny filled with dirt dauber wasp nests. If it was hollow and had an opening, there was a dirt dauber nest in it. Here is what came out of just the passenger side lifter arm:

And there is the lifter arm frame after sandblasting:

I hope to have both lifter arms with gearboxes and the front bow painted this weekend and hopefully all of those parts back in the car to start aligning them. I just got the new tack strip material in today and that was the last part I needed for this set of parts.


So the first coat of paint has cured on the front bow and I sanded the part that you can see when the top is up to give it a second coat.

And I gave it a heavy second coat.


I also cleaned, blasted and painted all the parts of the passenger side gear box.

I then put the gearbox back together.


The next parts are the latch handles. I have two sets so I'm going to just clean both sets up and put one set away as spares if I ever need them. One of them on the replacement top had a bent spring retainer but that was easy to bend back. I sandblasted all of them and I scotch brite wheeled the pot metal handles. All of the handles has a bit of casting flashing and general nicks and scratches that needed to be buffed out.

As of right now, the paint is drying on both sets of latches.


Since I have decided to move the replacement top material over to my existing frame, I needed to remove the material off of the old frame. There 6 separate parts that make up the top cover: the front seal, the top, the pads the rear curtain w/ the rear glass, the well liner, and the gutter. They come off the frame in that order so you start at the front and work your way to the back. Here is the front seal attached to the front bow.

With the weather stripping removed, you can see the staples that hold the corners down.

Once the corner staples have been removed, you can then fold the flap up and take out the remaining staples that hold the front seal on.

At this point, I realized that the 2nd bow was already loose and needed to come off before something got damaged. You can see that about 8 inches of staples had already been pulled out. This happened because the joints on the linkages that move the 2nd bow are worn out and the bow was binding up when it was opened.

I marked the center of the staple tack strip so I could center it back up and pulled the 2nd bow out completely.

Here is the bad ball joint on the 2nd bow and what a new one looks like.


With the 2nd bow out of the way, I went back to the front bow to get it completely removed. Under the front seal were more staples that held the top itself to the front bow.

Like the strip for the 2nd bow, I marked the center of both the front seal and the top for alignment on the other frame.

After all the staples were out along the front, I was able to peal it back off the front bow to expose the side flaps. The installer had glued the front flap to the front bow. It's supposed to be stapled only, not glued. I think I can clean all the old glue off though.

This front bow is bad. It's not completely scrap but it's close. The corners are rusted out and all the tabs that hold the tack strip in are rusted off and gone. Rather than replacing it, they just glued the tack strip in (poorly).

Another thing I noticed is that this was not the first replacement roof this frame has had installed. I could tell that the tack strip had been replaced with an aftermarket one but under the top, there were old staples and bits of an old top that had not been removed before this one was put on.


With the front loose, I went around to the rear of the top. I made some alignment marks on the top to get it lined back up with the rear curtain and started pulling the staples around the rear sides.

Another install issue that I noticed was that they did not use stainless steel staples and they were starting to rust.

I pulled all the staples around the drivers side an peeled it up off of the rear tack strip. You can also see a test spot where I scrubbed it to see how clean it will come.

Next, I folded the top frame up to expose the rear quarter window upper weather stripping. This piece retains the top around the window opening.

That section was supposed to just be held in with the weather stripping but it was glued also. I then moved over to the passenger side and did the same as the drivers side.

Next I had to remove the staples from the 3rd bow. It's very similar to the 2nd bow and just has a flap with a carboard insert to stiffen it up.

Lastly, there is a big zipper that holds the top to the rear curtain above the rear glass.


With the actual top off, next is the pair of pads. The protect the seam in the top and pad it from wear on the frame mechanisms. These pads are completely shot and they just fall apart in your hands. The only thing left of them is the upper liner. The foam and the heavy inner liner just crumble in your hands. They were screwed to the front bow, stapled to the 3rd bow and just the foam and upper liner portion continue on to the rear curtain where the foam is glued down.

Once the pads were off, the rear curtain with the rear glass is accessable.

The white part is the apron and is the only fabric part of the curtain that is visible when the top is up. It's stapled along the rear tack strip.

With the staples out of the apron, the curtain is exposed. It was supposed to be stapled down but the installer just skipped that step. I pulled all the staples around the sides to free the curtain from the rear tack strip.

The last thing holding the curtain on was a row of staples on the 3rd bow.

With the rear curtain out, next was the well liner. It did not have many staples holding it on.

Lastly is the gutter. It does what it sounds like it does and directs water to the body drains.


While I had been working with the rear tack strip, I felt like something was wrong with it. The tack strip material was loose in the track on the ends and when I got down to the gutter, I found that it was installed completely wrong.

The gutter is supposed to be stapled to the rear tack strip and just allowed to drape down on the outside of the tack strip. This installer stapled it on upside down and wrapped it around rear tack strip and let it drape down on the inside of the tack strip. This caused two problems: the gutter is now too shallow and lets the water pool up inside the gutter itself, and the water wicks that are supposed to go down the front of the inner wheel wells to the body drains were just cut off because they would have gotten caught up in the top mechanism. This let water spill under the back seat and into the trunk. Another issue with it installed incorrectly is that it was too tight and ripped on one side. Fortunately, the gutter on my old top is salvageable and I'll reuse that part. Once I got the gutter off, this is what I found:

This rear tack strip is garbage. It's completely rusted out and was like that when they put this top on. The tack strip material was missing out of most of the channel and was replaced with the wrong type. On top of that, since they used the wrong type, they had to rivet it in just to get it to stay. Since they tried to rivet it in to rust though, they rivets just popped out.

On top of that, the front 18 inches or so of the passenger side was just completely rusted away. They cobbled in a piece of Home Depot C channel to replace the missing part but that just barely worked to get it out the door.

What I don't understand is why they even bothered wasting the time to botch up the rear tack strip when you can just order a brand new one for not much money at all.


While going though my collection of parts I noticed that the rubber seal on the replacement passenger side gearbox was in better condition than my existing one. One clip and one rivet later and I had it swapped over.

I also found that a specific carriage bolt on the replacement frame seem to be of a revised, stronger design. My existing one was worn so I swapped in the different ones.

Next I mounted the drivers side lift arm to the gearbox and mounting frame.

With this arm assembled, I mounted it back into the car.

The arm was a little long and the front guide pin missed it's hole.

To correct this, you adjust the stop at the middle hinge and that adjust the length of the arm by allowing the joint to pivot more or less at that point.


After putting the drivers side arm together and back on the car, I found out that it's much easer to just put it together in pieces on the car rather than building it on ground and then mounting it to the car. I mounted the bracket first.

And then the arm to the bracket.

And finally, the gearbox to the bracket and the arm.


I put a new tack strip on my front bow. You can see the tabs that hold the tack strip in that were missing on the other front bow.

And finally I bolted the front bow to the two arms.