I am replacing a 1 1/2" tub drain with a 2" shower drain. The existing 1 1/2 PVC Tub Drain leads into 2 " on the main sewer line. Is three a way to remove the 1 2/2 line (maybe ream out the 1 1/2 pipe thats fitted into the 2 "??

Can you make it all 2"?
http://www.ronshomeandhardware.com/1-1-2-PVC-Box-Adapter-p/114838.htm?click=1014