FYI, most of the posts on this thread about IGH service are old info. The newer Shimano Nexus (8R30/31 and 8R35/36 and Alfine are very well sealed as is the SRAM i-Motion 9. There's no need to drop $100 for Shimano's "special" lube, synthetic ATF is beng used by many folks with good results, only $5 per quart.

Here's a link that explains the differences between old and new Nexus hub's sealing:
http://www.astounding.org.uk/ian/hubgear/index.html