shifter/gearbox rattle

[VanderPut]

So, my car has decided to create a new rattle.(a 05 MT base model)

while driving up until 90/100(KM/H) (55/60 MPH) the car is fairly silent,
then at speeds upwards of that, a rattle starts to come from the shifter, regardless of gear(4th, 5th or 6th) and clutch being engaged or not.

after a while, I got furious with the thing, so I took out the plastic console between the seats and drove around to check the origin a little better.
As it turns out, the rattle is coming from within the shifter, at the very bottom, under the sealing rubber, where theres the plastic nylon piece.

at that stage I decided to close up the parts and call it a day because its too far into the gearbox and i dont want to mess with it myself.

does anybody know whats the cause of this rattle? before anyone mentions it, i know its not the metal spacer on the shifter knob, because i drove it without the knob to test it out.