Many users of the BCG800XL SmartGrinder experience jamming and a horrible gear-stripping / grinding noise sort of sound at some point.
Here's a 10-second video I recorded of the problem / symptoms:
This is usually either a worn out impeller or stripped drive gear. The main symptom of a worn impeller is it'll jam and the motor will bog down even at a coarse grind settings (which should be easy on it).
The BCG800XL smart grinder has an impeller that sits underneath the steel burrs. Its purpose is to push the grounds out the chute that leads to the basket (or espresso portafilter). When the blade fins wear down over time, the grinder begins to jam up because it can't properly expel the grounds anymore. This often gets mistaken for a problem with the main drive gear when a stripping sound comes from a torque limiter mechanism. You can tell if you simply remove the burrs, and look at the gap between the cylinder wall and the impeller blade tips. If it's more than 1 mm, then it's probably worth replacing. If you can take the impeller out without dis-assembly, then it's definitely worth replacing (A good impeller is wider than the hole and can't just come out).
Breville unfortunately doesn't sell parts, so this tutorial has been made possible only recently by 3D printer technology ( I've designed an upgraded impeller for the BCG800XL and made it available here: http://www.shapeways.com/product/NASLAGCCP/coffee-grinder-impeller-upgrade-for-bcg800xl?optionId=59828418 )
Here's a quick two minute overview of this replacement part:
This guide will walk through impeller replacement to fix the most common cause of jamming with the BCG800XL Smart Grinder from Breville.
Special thanks go to the folks at Dunlap Public Library (dunlaplibrary.org) who helped greatly by printing prototypes for me.