I recently bought a house that has a tub/shower with the 3-stem configuration (hot, cold, diverter). All three stems leaked from the stems, plus when the diverter was switched to shower mode a stream of water would still run out the tub spout (about 10% of the flow) so I replaced the hot and cold stems and rebuilt the diverter (couldn't find an exact replacement). I also replaced all three seats.

The rebuilt diverter no longer leaked but still allowed water to come out the tub spout while in shower mode. After about a month, it's letting more through. I'm beginning to wonder if the previous owner put in the incorrect diverter valve, but I have no way of knowing what diverter valve would be the correct one!

Any insight is appreciated -- thanks.