China Southern Wuhan layover... do I need to go through customs and immigration?

I have a 2.5 hour layover, flying San Fransisco to WH, 2.5 hour layover, then WH to Saigon. Both tickets were bought together on China Southern. Does anyone know if I will need to get a go through customs and immigration (enter and leave China) just to catch my next flight? And if so, will 2 and a half hours be enough time to do that? Thanks