Help me identify and remove this Delta shower faucet

[Drfranks]

I put a pipe wrench on the chrome piece and turned it clockwise many times. It doesn't seem to unscrew. It feels like there is the constant friction from the rubber ring when I turn it. I tried wiggling it straight out but was afraid I would break something. It didn't seem to budge. Trying to fix the constant dripping.

I see another thread says it is a 1500 Series Pressure Balance valve. What is the trick to removing this? I presume I don't turn the white plastic nut or the big white part (probably the cartridge).

 

[Terry]

The chrome tub slides off. If it's Delta, there will be a round brass thread on, which can be difficult if it has become stiff. I sometimes use heat to expand that brass thread on, and then spin it off.