Will I be able to fix this shower/Tub Single Handle Valve Trim myself?

[diy]

Forgive me if I am naming this item wrong. I think it's called "Single Handle Valve Trim". Right now it does function ok. But when I turn it, it feels something inside is "loose". I think it's due to 15+ years of wear and tear when turning. It feels "empty" when the turn is right around the middle of the complete turn.

Are there anything I can replace to fix the turn so it feels normal and secure as new?

Thanks!

 

[breplum]

Usually there is an allen screw holding the handle on. With the handle off you can potentially replace the cartridge or not.