My wife and I were all packed and ready to go to WCR19 waving goodbye, she wanted to open the window. It did; all the way. The plastic button had escaped from the moving dog. A new plastic button did not really fix the problem, but it worked for a while. Then I decided to go to the lathe and make a button from bronze and attach it so it can't fall off.
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The button didn't pop off, but the window wouldn't roll all the way up. Looking closer I found this issue:

The worm gear track follows a plane. For most of the travel, the dog that actually does the lifting is sticking up, normal to that plane. That is, the grove that the dog slides through
Most of the way, the dog looks like this. Drinking straw added to make things clearer.
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See, straight up and down.
But as the window gets to the top, the tube bends like a switch back on a trail. The engineers must have assumed the slot would stay straight. But it doesn't.
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This is an extra track from eBay. The angle doesn't look that bad, but what it does is to wrench the dog out of the button. When they were new, I suppose that there was enough hold upon the button to make it through, but here where the dog is towards the top of the run things get stiff even if everything stays together. The top of the run is where my bronze thingy jammed. It wouldn't allow for that twist of the run.

My solution was to take the worm screw completely out and reshape the slot in the tube that houses the worm. You should take the worm out anyway to clean and lubricate it. Then you grind away where I have marked with paint pen. Not enough so that the drive worm is thinking about popping out, but enough to let that dog keep facing the little plastic button. Also, you need to make the transition smooth so the dog doesn't catch at the spot you started or ended the grinding.
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This worked for me, and although I don't horse around with the window handle, the window so far has stayed put together.

Now with my TR6, I went overboard. It has the scissor type drive as found in the later 914s. I cleaned and relayed so much that the window drops from its own weight.
@Literati914 , @ClayPerrine

Great, thanks for the thorough explanation!! I’m gonna definitely do this when putting my doors back together. Would you say the bronze item is not necessary.. think the original plastic item would be fine, considering the mod to the track/tube ? Also, how long has your mod been in use so far?


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The way the mechanism is designed, it is hard to come up with a better solution than the plastic piece , and 914Rubber makes them. I was able to fit a cutoff wheel into the slot, but a sanding disc on a roll base might be better. I am curious what other folks with more experience than I have think about this fix.
Good luck with your restoration. I am working on my '76, with the reinforced doors. I like the idea of side impact protection, but my son Doug points out that the bumper of the opposing vehicles these days would probably be at window height!

I would suggest that you upgrade to a late window regulator and track mechanism. If you are not doing a coucour level restoration, using the later regulators makes the windows work much better.