Not sure what to do with this, I am remodeling the upstairs bath and decided to replace all the plumbing in the house since it is all old leaky galvanized and the main sewer stack has been leaking. well this is the last three feet above the floor. it WAS a 4in line now about 2in. when i cut through it about half the pipe was thin (cut fast like butter) can this be salvaged or do i start tearing up the floor???
any help is appreciated.
thanks

I would at least remove the section of pipe connected to the cleanout fitting and replace with plastic. Be sure to have the remaining cast iron drain under the slab cleaned before rebuilding the stack.

Cleaned? You mean with a snake? I'd bet the snake would chew up that rusty ole relic.

I say start digging

Unfortunately digging up the basement is not in the budget this go around. I have a lead main for supply line that i am thinking we will replace next spring and i can do the sewer lines then since the yard will all be dug up anyway. more or less just looking for a bandade right now.

my band-aid approach would be scoop out (shop vac) the gunk from inside that pipe down to the elbow at the base. attach right onto the pipe where you cut it and run your new plastic pipe. put a cleanout right there in case you need it. that lower cleanout may never open and you might destroy the pipe trying to open it.
if you are going to replace it next spring, why go thru all the fuss and mess of trying to clean it outside?
if it turns out the gunk restricts the flow that badly outside, then use your new cleanout and have it cleaned.

My advice would be to exit the house above the existing sewer line as high as you cqn. Get it outside in the dirt quickly and make a tie in outside downstream of the base elbow.