default wrote in
:

Can someone give me a heads-up and/or link to more info on a DIY
repair.

I've got a combo tub/shower with a common three-handle arrangement,
the center handle switches from tub faucet to shower. Unfortunately
there's no brand name in sight. I've replaced the rubber washers in
the hot and cold valves numerous times. Lately, the tub faucet
dribbles a fair bit in the shower position. I think it's getting
gradually worse and I'd like to fix it.

My shower is tiled, and there's no easy access to the back side of the
plumbing; the other side of the wall is in a closet, covered with
drywall. I'm hoping to get some knowledge before attacking this. Is
this a reasonable DIY repair? Simple like a washer, or hard like
replacing the entire valve assembly? Will I find repair parts in the
big box or hardware store? Can it be done from the front? If not,
maybe by breaking though the drywall on the other side of the wall? Is
this going to lead to a bathroom remodel?

TIA,
Joel

See #11 in this diagram. It will give you an idea of what the cause is.
For this particular Central Brass one, it is called a Celcon Washer.
Looks like just white nylon.

http://centralbrass.com/documents/PA...DOWN/B0950.pdf