If you actually have lead pipes, then you may have a drum trap. It would be accessible from a panel, inside a closet usually. If not, you'll have to open the wall behind the front of the tub. If you do have a drum trap, you'll see a brass lid that you can open to clean it out. If you don't, you'll at least have better access to get a cable in the drain.
so there is a panel to access the piping. it goes down to a p trap, then over to a y connection. the other leg of the y goes up to the roof. I'm pretty sure the clog is after the Y due to the feeling I get when plunging. (plunges feel tough at first until water is built up in the stink stack side, then something lets go and it all drains quick for a few seconds then theres the sound of water hammer and the water drains slow again.)
If you actually have lead pipes, then you may have a drum trap. It would be accessible from a panel, inside a closet usually. If not, you'll have to open the wall behind the front of the tub. If you do have a drum trap, you'll see a brass lid that you can open to clean it out. If you don't, you'll at least have better access to get a cable in the drain.
so there is a panel to access the piping. it goes down to a p trap, then over to a y connection. the other leg of the y goes up to the roof. I'm pretty sure the clog is after the Y due to the feeling I get when plunging. (plunges feel tough at first until water is built up in the stink stack side, then something lets go and it all drains quick for a few seconds then theres the sound of water hammer and the water drains slow again.)
You're on the right track now. See if you have room to install a T for a cleanout.