I'm nonstop from Detroit MI, USA, Delta Airlines, to Beijing & arrive 2:45 pm.

I will transfer for a 6:45 flight to Changchun, Delta ticket on China Southern Air.
- Are they in the same terminal
- will my luggage be checked through to Changchun?

If it's not checked in, do I have to 1) retrieve luggage and 2) go through airport security as if I'm starting over?
Or, do I have to retrieve luggage and just re-check with China Southern Air, hoping it's in the same terminal. I have 4 hours between landing in PEK and departure to Changchun