Center Rear Differential rattles when starting up

[ptl69]

I’m not sure what’s my car doing when I engage it; it does this once in a while. When I start off my car in first gear, it starts rattling in the rear like it’s trying to grab it (like a bad clutch trying to grab). However, I am changing my clutch soon; I wanted to know if you guys think if there is something wrong with the center, rear diff or ACD so I can ask them to look at it also.

Thanks for your guys help.