I had the same problem with my 8ball knob as others have too... I think its to do with the weight being different making the knob vibrate differently, & also the material it's made out of... What is your new knob?
I remember reading in Cisco's Micra files that the noise us very common & Nissan are aware if it which effects how they make the gear knobs with regards to weight/materials. I remember there being a guide on there, like in the bit were he has FAQ section, were he describes how to reduce the noise.
I don't think you'll be doing any harm? I had mine on for ages no problem & I know offers have had them on for years...