Great post, and I just wanted to add a little followup on the Froggy video that BOMBSHOP posted.
This worked for me. I found the video very longwinded and thought he went a little overboard with everything.
For me, I checked the slop in the worm gear and there was a good bit of axial play.
I took the motor out, checked it by touching a 9 volt battery to the two input tabs (lines up perfect).
Once I knew motor was good, put it back in and used a flat head (actually I used a butter knife cause I was too lazy to go outside :P) leveraged against the motor housing to push the "key" forward so it was tight against the worm gear.
I was in a hurry so didn't take pictures, but I sketched it out. Hopefully this makes sense.