FLM aluminium tranny case

I use the case myself and it works flawlessly. In fact, it wasn't until I used this case that the tranny finally felt like a quality meshing machine. Which case are you running..Pede, E-Maxx? I assume a pede case from the parts you mentioned. You should make sure the innards are spinning freely before mounting the spur, and work your way in to the problem. You could measure center to center at all the shaft and outputs and compare to your plastic to see if you have a bad case. I can tell you though, if you get a good case the tranny is transformed to a beautiful thing....free of flex and precision mesh.