I used the dental floss trick successfully to re-thread the rear derailleur cable.
I have broken the dental floss 4 or 5 separate times trying to pull the cable end through the end hole. Seems to be a rough spot as well as the sharp bend upward.

I got my new (old) wheels today. Hard to believe this bike and most of the components are 20 years old.

So I'm going to try to thread it again. Any helpful suggestions welcome.

For internally routed cables I use a strong magnet to guide the cable through, and a pick (or the end of a spare spoke) to fish the cable out.

See if the bottom has a removable plate that gives you some access to the cable as it comes down the DT. If not, I've used weed trimmer line to go through, then taped it to a cable and pushed the cable, gently pulling on the weed trimmer line so as not to pull it through the tape....


The weed trimmer line is stiff enough, but has a curve to it that helps on the far end.

Thanks, but this is not like on a steel frame or even the brake fittings. There is a small plate riveted on that has a hole just slightly larger than the diameter of the cable. The solid bb shell is very hard even to get the cable around. Below is a picture of the cable threaded in backwards.

The only idea I have come up with is to do the floss and vacuum trick in reverse, and then solder/splice the shift cable to that wire and hope the splice holds and is not too thick to pass... I'm not up to trying this yet.