Probably a simple solution?

[urbanplumb]

I just haven't found it yet.
This shower was a gift from previous owners, not sure what their plumbing experience was but I assume from other things I've found in the house, it was not very broad.
Anyway, the drain itself appears to be made of brass, there are no threads so I took my best shot and purchased a 3" pvc snap-in drain, which was a bit to large to fit inside the drain. My educated guess is that the pipe shown in the photo is 2 3/8".
My question is how am I to approach this issue to keep it from leaking and thanks for any help.

 

[Mr_David]

Looks like you have 2 different pipes in the drain.
One inside the other. ???
This might help, Have to leave but if you're on a concrete slab this won't help.

http://www.plumbingforums.com/forum/showthread.php?t=2136

 

[urbanplumb]

Well I was afraid of that..the good news= I have plenty of crawl space...the bad news= in order to get to the fitting I'd have to tear out the wooden floor underneath. Guess I was hoping there might be some kind of connection that would tighten up underneath the stall floor...
Thanks for the tip

 

[Mr_David]

I use a large basin wrench to tighten the nut.
I used a drill to split the nut to get it off.
be careful you don't drill through the fiberglass pan.
You will hit a thin rubber washer before the pan.
If it's the pipe in the fitting that leaking then then you need to figure out why it looks like 2 pipes before you can find a solution.

Looked again the black or darker ring is the bottom of inside of the fitting. If the flange is solid and tight to pand just pack the fitting with oakum and lead wool