I know what it is,It's a round black plastic piece......sorry I couldn't resist. unless it was on the outside, i can't think of what it could be, but it shouldn't have been inside the diff. I would take it or pics of it to your local kawasaki dealer and ask them. you'd be surprised what they find when servicing vehicles and they might have seen this before. if not, change the diff oil and and you should be fine, but you might check the oil level frequently to make sure it is where it needs to be. to be safe you might want to change it again to be sure, if nothing else comes out, you should be fine. drain it and fill it again, if nothing else comes out I would think you are good to go. if it's under warranty take it to the dealer and have them go through it.
it cant be very big if it came out the drain hole. Keep us posted on what you find out. it could help others on here. it won't help me, I'm perfect and never make mistrakes
I still don't have any ideas as to what it is.??
I hope somebody in here knows, my only guess is something done in production at the factory, like a temporary plug to keep dirt out before the real drain or fill plug was screwed in.? I hope you find out