GE Trash Compactor hums
 

I activated the ram and it stopped in the down position. I have turned the chain to return the ram to the top. Looking from the open top down I can see that the side parts that are attached to the ram are well greased. When I close the door the unit hums. I have checked the foot pedal and the start switch which appear to be working correctly. Does anyone know what I should do next? Thank you.