I'm hearing a hissing sound when I pull the diverter valve for the shower and the water pressure is bad, so I'm guessing there is a leak somewhere between the valve body and shower head.

Last time this happened in a different house, I found the nipple for the tube spout was leaking at the valve body due to a lack of thread tape. I pulled off the tube spout on this shower to find it wasn't a threaded nipple, but just soldered copper pipe.

Could the diverter valve or seal on the spout cause a hissing sound and bad water pressure? The spout doesn't have water coming out of it, so I'm not sure how it could be the spout.

I don't have an access panel on the back side yet, so I thought I would pull off the handle and see what I could from the front side. After a lot of cleaning, I got the set screw out of the Moen single handle. Now I can't get the handle off the spline. If I try to pry, the whole valve behind the surround moves. Any ideas how to get the handle off? Am I waisting my time with the handle and should just cut into the drywall on the other side?

Keep in mind Moen stands behind their products for life so a replacement cartrdige will not be costly. Remove the handle by prying off the small plastic cap on the handle then the Phillips screw, pull handle straight out at you. Now remove the 2 screws holding the escutcheon plate and you should be looking right at the cartridge, some havd bult in integral stops to close the water or you may need to shut down your main. Are you still with me? http://www.masterplumber.net/moen.htm