My AA260 has an occasional heavy 'rumble' when it's runing,, the 'rumble' and vibration seem to come from the transfer head, but at times it seems that it's coming from the support bearings, .
I took the two brass half moon bearings out an turned them over, and mounted them swapped top to bottom. with the oil hole on top, I made a small cup and keep gear oil in it..80w-90wt. just a few drops every now and then,
My auger is getting worn, so the slot for the brass bearing is worn and there are other reasons it can make noises..
Thankfully my AA is out in the shed in the back yard,, but noise and vibration is not good for machinery,, it is the machine crying for HELP11
So it's good to chase down the cause..
I have taken a rubber mallet and whacked the tranfer head and this usually stops the noise so I'm thinking its the combination of the worn brass bearings and the worn slot in the head of the auger tube.. allowing too much room..
The auger is pretty much balanced on the the support bearings, so anything to set up a vibrations will continue to vibrated..