Does anyone know why my speedometer cable "screeches"? It's a A833-OD in a 1966 Dart SW with a 360 V8. I put in a new cable, double-checked the correct length with another car (same year and model), lubed it generously and it still screeches! It sounds like it's at the tranny end rather than the speedo end. Mystified. Could it still be too long? (too short and it wouldn't turn, right?). Many thanks.

Yes, too short and the cable will not turn the speedo.

If you have an extra cable, it would be easy to shorten it and give it a try.
"Funny noises" are always hard to trouble-shoot, one other check would be to disconnect the cable at the speedo end and drive the car around, then try pushing on the rotating cable end to see if the "screech" presents itself.
(Proceed at your own risk... keep long hair, loose clothing and other things you value away from rotating parts)
DD