This modification to the Replicator extruder rotates the fans to the back and the extrusion motors to the front. I did this so I could see the ends of the extruder motors so I could better gauge the rate of extrusion. This also puts the delicate fan blades in the back so they are better protected.This is not a object build but rather a modification to the Makerbot Replicator. While I have a dual extruder, the modification should work for the single extruder version also. Please read the attached PDF file and understand the risks involved before doing this modification.Now that I can see the shaft, I can better judge if the filament is slipping again the pinch rollers.In the attached picture, you can see a white ABS disk that I glued to the end of the left extruder motor shaft so I can watch the extrusion speed.