My drivers side window has always been abit stiff and screeches a little too, Ive just fitted an electric window motor to that window which showed just how stiff it was as the motor really struggled, I took off the felt? guide thingy towards the front of the door as I was planning on getting new ones anyway and it loosened right up and now runs smoothly, so that was clearly the problem, but my question is, Do I actually NEED to replace it? what is it there for anyway? Window seems to go up and down quite happily without it...