I also have a tub diverter spout that's not working right; water still comes out of the spout when I pull up on the lever. From reading this forum, I'm sure it needs to be replaced.
Previous answers say that the spout is either a "screw on" or a "slip on". I checked underneath the spout and it has a slot at the wall. Assuming it was a "slip on", I got out my allen wrenches, got underneath the spout and tried to find the set screw. As far as I could tell, this spout doesn't have one.
Could it be that the slot is there as a grip for some sort of tool?