1953 Chevy Belair

Sounds like either the end of the cable is worn(could be where it goes to the speed or the end going to the tranny) or the gear in the speedo where the cable goes in, or the gear in the tranny.

You got to always be looking for parts cause they are getting harder to find all the time no matter how simple the part is that's if you aways want to cruse

A 60 year old speedo needle might need a drop of oil.

I'm sorry but some of these questions need just a little common thought and your on this site you can find new and used parts all the time if you have a computer if you really can't get a hold of me I know I'm an#l thats why my first wife left me caught me sleeping with the car

My money is on the speedometer needing a little TLC. Check the cable also for wear or kinks or bends that may slow the cable. It also may be the gears in the trans, but that is the last place to look. Lube the cable with the correct grease, make sure it runs easily and smooth. Put a variable speed drill on the speedometer and see if it will go continually up to the top speed if possible. If you live anywhere in So. Cal. There is a speedometer shop in Costa Mesa that is magic. They work on units from new cars to 30's American cars. Very reasonable and they will talk to you about the unit.