I bought the car from a private dealer, the car is...

I bought the car from a private dealer, the car is 2 years old, and still have 2 years of factory warranty left. The car has a strange popping noise coming from inside rear left door panel and inside rear deck from time to time, especially when I make a right turn, I can duplicate this noise every time. Took the car in to have it checked out, and also asked the dealer to inspect the car to see if there is anything wrong with the car. Received a text message towards the end of the first day, the car needs to be left at the dealer for overnight, talked to service adviser, and was informed will let me know once the car is ready to be picked up. I received no email, no phone call, no text message about the status for my car for next day. On 3rd day, around noon, I contacted the dealer to find out what is going on with my car, just to find out the car has been ready since the previous day. The dealer told me the popping noise was coming from the limited slip differential, although I don't have great knowledge about LSD, but, I know for sure, it's not coming from the LSD. I am not sure if the dealer has enough knowledge about this particular car. I was told they did the inspection and found nothing wrong, and they did not charge me anything for the inspection. I am not comfortable about the lack of communication. I'll try another dealer located at Lynnwood and see if they are better.