water tank?

Hi all

the ballcock/valve was not shutting off [old age] so renewed it but now when water is filling up in tank the valve rod to ball is juddering and bouncing about until it shuts off, there was a bit of play between valve & rod arm put in a small washer this has made it a bit better but it is still juddering every now and then right down to taps in sink ?

Frank
May 2012