I hope someone can help me, as I am a newbie, to this forum and plumbing. I believe I am working on an American Standard shower faucet, trying to fix a leaky faucet. There are three knobs - Hot, Cold and diverter. I removed the hot water knob and the outer sleeve. Then I removed the putty and cut some of the surrounding tile to see what is behind the stem, only to find out that there is No hexegon nut. There was an attached sleeve on the stem that I kinda broke off, trying to turn it, it broke off at the base showing a couple of threads. It looks to me that this stem screws into the brass fitting somehow. How do I get the stem to unscrew with out messing everyting up. Please keep in mind, there is nothing on the outside to unscrew, somehow it screws into the fitting.