Shower drain replacement

[afink]

Hello, new here, but have some questions on replacing a shower drain. Needing some advice on how the assembled pieces come apart. I will enclose pictures of how it is assembled.
I purchased a tub wrench and was turning it counterclockwise and could only turn the drain about quarter of a turn untill it had quite a bit of resistance so I turned it back clockwise and then counterclockwise a quarter turn to resistance and the barbs in the drain broke off.
I'm just wondering if there is a certain way of taking this apart?? I wasn't expecting that much resistance to unscrew the drain it was flexing the 1/1/2 drain pipe it connects to when I had pressure on it turning. So I need some advice how to replace the drain and possibly put a new rubber gasket in there or new assembly. Thanks

 

[breplum]

1. shower drain is supposed to be 2" to modern standards. (I have a 50's house with same too-small drain)
We cut out everything below and start fresh.

 

[Twowaxhack]

You can’t take that drain out without removing the pvc first. Then the nut holding the drain can unscrew. Then the drain lifts out from the top.

 

[afink]

You can’t take that drain out without removing the pvc first. Then the nut holding the drain can unscrew. Then the drain lifts out from the top.

Sorry for late reply. Okay, so I should remove the pvc pipe assembly and then pull it out through the top of the tub to be able to unscrew the the large black nut? And then remove the drain from that? I saw that there is a connection on the outlet side of the s drain where I can possibly unscrew it. Thanks for the help.

 

[Twowaxhack]

Cut the pvc where I marked in red, all the way through.

Then unscrew the pvc from the shower drain.

Then unscrew or cut the nut off that I marked in blue. Be careful if you cut that nut off, don’t cut into the fiberglass shower.

Then lift the drain out from the top side of the shower.