Hi, the drain in my tub has been horribly slow for quite some time... I've tried to clear it wish minimal success... I thought it might be the old drain stop, so I took off the lever face to discover that it had corroded and separated from the rod or chain that connected it to the stop... Any tricks on getting it open, or do I have to take the pipe apart? Thanks...

Can you reach down inside the overflow with a bent wire coat hanger and fish the linkage out?

If the waste and overflow is accessible from a basement or crawl space, you might be better off replacing the whole thing.

Put a very small "shepherds hook" in the coat hanger and try to hook the cross rod on top of the plunger. Good luck, Tom