speedo needle keeps falling lower

[1981C10pos]

I got an 81’ C10 that keeps having an issue with the speedometer needle, it won’t drop to the same spot when stopped and it keeps throwing the whole gauge off. I will take the cluster off and reset it to the proper resting position and it stays where it should for a couple days to a week then drops way below. Does anyone have any explanation to why this might be happening before I deal with replacing the speedo wire and housing on the trans.

 

[squaredeal91]

Sounds to me like the needle might not be holding onto shaft tightly anymore allowing it to change positions.