I think my 2018 72" X3 Rc Smart Lock Diff needs to be replaced. I could feel in the pedal pulsate/vibrate when I would put it in 4x4 so I went to change the fluid out and there was barely any in it. Maybe 2 or 3 ounces. I bought it used the previous owner said nothing was wrong with it I bought it out of state. I got it and knew something wasn't right. He is no help but that's life. Anyways I changed the fluid and like I said there was barely anything in it and I had small pieces of metal sticking to the drain plug which I was like that is not good to have metal pieces. I poured some new fluid and took it out and felt the same thing. It's hard to describe but once you are just cruising and you put the 4x4 you can feel it through the peddle vibrating really bad and I can hear it slightly but it literally feels like it's binding up or something. Like I said it's hard to explain but it feels horrible. I can smell diff fluid too and it;s not leaking. I assume with the metal shaving like little pieces it's toast. I mean it still works but it literally feels like something is just pulsating hard and fast on the gas peddle it's horrible. What are my options? Can these be rebuilt? Should I send it out to someone or can I do this on my own? Thank you.