Hi, I was taking out the assembly, took out the 3 nuts just fine, but then the fourth one is covered in rubber which i took off, and its some cone shaped contraption instead of a nut. What is this? And How do I remove it to take the assembly off? I am not a car guy whatsoever, so I am completely mystified why they would even do this in the first place. Why nut just put 4 nuts on? Thanks for your help in advance to remove the assembly.