I replaced the stems on a 1972 vintage American Standard Colony set. I fished 'most' of the peaces out of the old ones, replacing cold, hot and divertor colony long stems (link below for picture of diverter) http://www.suttonplumbing.com/pc-470...rter-long.aspx

I have good pressure but from the gitgo I was bypassing too much water to the tub spout when fully diverted to the shower. I finally called a friend, a full time plumber to come look at it.

He took it out, did what he wanted and put it back. Still bypassing water. He said give it a couple weeks to fully seat. (Fine freind, huh?)
Well, a couple months later my wife is about to kill me if I don't fix it.

I pulled it out and it tried to stick like the old one when I pull it. When I got it out, the backing screw stayed in. Fortunately this one didn't fall down the valve body and I fished it out.

Now, the questions. Do I lock-tight that sucker? Tighten it down tighter against that nylon bushing? What is grabbing it and working it out as the diverter is rotated?
Why can't I get more water to divert to the shower? No probs fully diverted to the tub spout. I could understand if I was getting water up to the shower when trying to use the tub spout. Like a partial obstruction from a dropped screw or stem peaces? I just don't visualize an obstruction up to the shower.

Any help is of course very appreciated.