Hi.  We have  63 plate KA Mk2 and the Gear selector knob buzz's when driving as the knob is loose. It didn't used to do this. This gear stick is the type that has the collar you lift to engage reverse. I have looked in great detail at it and can't see how it comes off or tightens up. I have looked through this site and all I can find is posts "thinking" it unscrews or might have a screw to secure it, it doesn't but no definite answer. Googling it didn't help either.

Has anyone got any ideas? Thanks. 

Finally got this sorted. There is a grub screw inside which tightens onto the selector shaft. Getting at it is the tricky bit. The front leatherette cover needs to come off. Be careful though. Use plastic trim levers to ease it off from the bottom and top simultaneously. For some reason I now have a small 3/32 gap at the top between the cover and the white part. Apart from that all is now good. No buzzing.  I might recover it and fill the gap in that way.