Someone please HELP!!!

I recently started having a problem with my shower in the main bath upstairs. Whenever I turn the water on, no problems. When I turned the diverter to shower, the water starting coming out fine and then the pipes would make a wierd sound and then the water would pretty much shut off (a small trickle out of the shower. Happenes when shower head off too!!!). When I turn the diverter back to tub, the water comes out of the faucet fine. I can get the water to come out of the shower ONLY if I slowly and barely turn the diverter on so that there is water coming out of both the shower and the faucet. If I turn the diverter far enough to almost cut the faucet water off, I hear the noise and the water flow stops. Note: This also happens with the shower head off!!!

Now I have replaced both the hot and cold water valves as well as the diverter valve and this continues to happen. I only seem to be having the problem with my shower. It happens if I use hot or cold water.

Sorry, one more note.

This is a Gerber (I believe) shower valve with the hot cold and diverter all in a row. The diverter is not on the faucet.

Gerber are decent shower body's when they work BUT are fickle.

I suggest you remove the diverter (Water valves can remain on) then open the Cold water side then the hot allowing the lines to flush out any debris.

Sometimes the diverter washer gets jammed inside the body causing this kind of problem.

Re assemble remove the shower head and try again.

ALSO Check the seat and washer on the diverter.

Stupid question... can this be done without ripping into the wall behind the shower? I have the same symptoms that just started happening in my shower this week.