If your American Standard shower mixing valve is causing water hammer this video will show you how to fix the problem.

In the beginning I tried water hammer arrestors which didn't work. I also made sure all air was bled from the piping which didn't work. I then set out to find a way to defeat the pressure regulator in the valve cartridge.

In older homes with old galvanized piping the hot water side usually becomes restricted. These cartridges have a hard time with the extreme pressure difference. It's my theory (but I'm no plumber) that the valve tries to limit the cold water side but goes to far and completely stops the flow. It then overcompensates and the diaphragm moves the other way allowing flow again but repeats the process thus starting a cycle of water hammer.