I just got off the phone with Shimano technical support asking whether they had a service manual available for the SG-S500 or 501 Alfine gear hubs. I was told that everything available is in the PDF downloads from their web site. I had already checked there and the only items available are the hub installation sheet and a parts list with exploded diagram of the hub.
How can Shimano offer a parts list of theoretically available parts and then not have a service manual available that covers how to install such parts? The whole thing seems to me to be very poor support on their part for their products.
They used to offer a service manual for the SG-8R20 Nexus hub as it is posted on the Harris Cyclery web site and I just printed it out, all 34 pages or so. Thank you Harris Cyclery.
IMO both Rohloff and SRAM offer MUCH better technical documentation for their gear hubs, including disassembly/reassembly and service instructions.
BTW per downloaded parts lists there have been three versions of the Alfine hub. The first has the SG-S500 model number on the hub not underlined. The second has the model number underlined and the third is the new SG-S501 hub.
End of rant! ;-)