SPS,
The main reason we use to pull down the tail is to have a look at the flex plate that connects the T/R drive shaft to the gear box. Always a good idea. You have probably noticed that there is an inspection hole for just this sort of thing. I remember a Robinson video (actually it may not have been Robinson) for flying schools that showed the pulling down of the tail boom. The only other thing that I can add is that there have been a couple of types of T/R gear box housings, one of which had a lower sight glass.
Hope this helps, cheers.