A plumbing problem that we can't seem to get a grip on:
When we turn the shower knob, the water still runs out of the tub spout. There was initially a piece missing (black rubber gasket type fitting) from the back of the diverter assembly, but now that this piece has been added the assembly either 1. won't set back far enough into the pipe to reach the line that feeds the shower head or 2. does not allow water to reach that pipe and the water shoots out of the wall.
Sorry, we do not know the model as it's a new home for us and all was existing, but it is a 3-handle in the wall style. Any thoughts?

BeforeI can help I have to know what I'm helping with. Does your tub/shower valve look like the one pictured below?

Yes, it looks like the diagram except that the pipe up to the shower head is set back behind the horizontal pipe that feeds the hot and cold stems.

"it looks like the diagram except that the pipe up to the shower head is set back behind the horizontal pipe that feeds the hot and cold stems."

Make sure they gave you the correct part. Did you replace the entire stem and washer assembly or just the washer? Try this. Take the diverter stem assembly out and turn the water back on to flush out the valve body. There might be a part of the old washer still in there that's blocking the washer from seating. Let me know what you find. Tom

Had the same problem. Try turning the diverter to the one position before screwing it in. that way it should turn off all the way, without blocking or diverting h20 down the spout. Don't know why, helped me.